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Author Topic:   2005 305 Conquest: Engine Mounting

Ricky posted 02-24-2008 08:39 PM ET (US)
Just read a thread on Verado Club site from some one in Canada that thinks his 2006 Conquest is bow heavy and believes he should raise his engines one hole (out of three) to top position. Informed consensus from that group was that he should. Indications were lots of spray from engines onto cowling, trim tabs useless as he never has to lower bow, and inability to get [engine speed] over 5,600-RPM. I have a 2005 305 Conquest with identical symptoms.
Actual discussion related initially to propeller selection but I think raising engines a hole or two has some merit, at least after reading some informed comments. Owner probably has to wait until spring to test his engines but I was wondering: Have any warmer climate users raised engines on Conquests? My 2005 has 5 holes and factory mounted in middle position. Is there enough cable and hose length to raise engines just by removing four nuts, raising engine, and re-bolting? Any other [concerns]?
East Coast of Florida has a lot of easterly wind in winter and with bow down pushes water up in air and wind blows it back over boat. Would love to reduce this effect by raising engines a hole or two and possibly have bonus of better fuel economy. Any thoughts?
jimh posted 02-24-2008 11:42 PM ET (US)
If you think your 305 CONQUEST is bow heavy, take some weight out of the bow. Do you have a big anchor and lots of chain up there? If you think about it, 50-lbs of weight at the very bow of the boat, multiplied by the length of the boat back to almost the transom, say 25-feet, makes a long moment lever, 1,250-ft-lbs.
I have a cabin style Boston Whaler, too, (a much older REVENGE 22), and I try to keep as much weight as possible out of the bow in order to keep the bow as light as possible.
As for lowering the engine mounting height, the only way I see that as helping to raise the bow is by creating extra drag at the stern. I think you'll be farther ahead by shifting weight toward the stern.
jollyrog305 posted 02-25-2008 08:15 AM ET (US)
I agree with keeping the bow as “light” as possible. Unfortunately, most of the storage in the 305 is under the V-berth/table (this also the location of the AC unit). I would also think that BW would mount the engines in the best/default location.
glen e posted 02-25-2008 08:27 AM ET (US)
take my word for it whaler buries the verados on a 305..we've raised several here in a fla....
Tom W Clark posted 02-25-2008 10:00 AM ET (US)
This is looking like a confusing thread in the making. Let's straighten of few things out.
For the most part, engine height and a bow heavy condition have nothing to do with each other. You are not going to compensate for one by changing the other. Both conditions should be considered but not with regard for one another.
At any rate we seem to have some conflicting advice. Jim is talking about lowering the motors on Ricky's Conquest while Glen seems to be suggesting raising them. Ricky is ambiguous as to what is being contemplated, taking about "raising" his motors to the top holes which suggests their lowest mounting position.
Can we have some clarification?
Ricky posted 02-25-2008 10:21 AM ET (US)
I am talking about raising motors. This means using the lower holes (there are five holes and my engines are mounted in middle hole.) The props would be closer to the surface is another way to say it. Don't want to lower engines as it would increase drag as Jim suggests. The thread on Verado site says cavitation plate should be visible when on plane. There were other parameters as well to determine engine height relative to transom. Person submitted pictures that indicated to those in the know that engines were too low in the water.
I am not sure what impact there would be on handling, if any, from raising moters but it does seem bow would ride higher but that is the cruxt of my question. Also fuel economy should improve due to less drag. If anyone has raised engines and experienced improved performance I would like to know so I can benefit from their experimentation.
Tom W Clark posted 02-25-2008 11:03 AM ET (US)
Ricky,
Yes, I agree that raising your motor *could* improve performance but that, by itself, will not make your bow ride higher.
A lot will depend on what propellers are on your motors. Some props are more tolerant of high motor mounting positions that others. Before doing anything else, I would recommend you try a pair of Mercury Revolution 4 propellers if you do not already have a pair on there now.
If the motors are now mounted in the middle of the five mounting holes, then the motors are already 1-1/2" up off the transom. Go ahead and raise them one more set of holes (3/4") and see how the boat performs. There is no harm in doing that.
In general, with today's good propellers, the AV plate should not be dragging in the water when the boat is on plane. With twin engine V-hulled boats like your Conquest, it is not a precise point where the AV plate is above the surface because the water coming out from under the hull is a lot higher on one side of the motor than the other.
On my 25 foot Whaler with twin outboards, I raised my motors one set of bolt holes and now I can see most of the AV plate through the spray at all trim positions and all of the AV plate when the motors are trimmed out to any significant degree. It is the outboard edge of the AV plat that is dragging if at all.
I have no personal experience with the Conquest 305 so I am not sure that the relative transom height on that model is, but if you can raise you motors at all, and get away with it in terms of propeller grip, then you will improve the overall performance of your boat.
A propeller with excellent grip like the Rev 4 will go a long way towards helping you get some bow lift.
glen e posted 02-25-2008 12:07 PM ET (US)
Tom - you are correct...when motor cowls are getting splashed badly, the motors needs to be raised...and with a bit of trim they are dragging badly...we just finished one down the street that was buried - raised unitl plate was wet, but out of the stream - went with rev 4 17's which trimmed way up get you in the right range, 5800-6400) albiet a bit low but everything was better....boat gained in all respects - what it really needs is a set of rev 4 16's or even 15's but they don't make them...In discussions with merc the 305 is the example we all give as to why they need a rev 4 15 counter....
Ricky posted 02-25-2008 02:29 PM ET (US)
Thanks all for input. Think I will start by raising engines a notch then address prop situation. Wonder if you can borrow/rent props to see how they perform. Noticed on one site rev 4-17's were $646 each. Think I will call "god of props".
Tom W Clark posted 02-25-2008 03:12 PM ET (US)
Ricky,
If you are in Florida, by all means, call Ken Reeves (dba Props Gods). He's a really good guy and can do better than $646 on the Rev 4s.
handn posted 02-25-2008 07:33 PM ET (US)
I have a 305 Conquest with 225 YamaMerc efi 4-strokes. It has the optional air conditioning mounted near to the bow.
In my opinion, the boat is not bow heavy for the following reasons.
The sweet spot in my boat is with the engines trimed all the way in (toward the center of the boat). The sweet spot is where engine revolutions and nmph are the highest for a given throttle setting.
Trimming the engines in pushes the bow down. YamaMercs are lighter than Verados. Verados would push the stern down even further and lighten the bow even more proving in my mind that the boat was designed to run most efficiently with the bow firmly in the water. The heavier the engines the less they would have to be trimmed in to find the sweet spot.
I believe the boat was designed with the following in mind. 1. It was designed for heavy Verados. 2. It was designed to give the best possible ride into a headsea. 3. The hull was designed to not only give a good ride but to give this heavy boat with moderate (20 degree) deadrise at the stern good speed and good fuel economy with moderate horsepower. My YamaMercs are rumored to be only 208 horsepower. Despite that the boat gets up on plane quickly and cruises in the low 20 knot range at 4100 rpm which appears to be the sweet spot for the engines and continues to deliver good performance when the boat is loaded with fuel and gear sufficient for a seven day cruise. 4. Last, and most importantly the boat was designed to deliver the aforementioned performance with the bow firmly in the water.
The downside is that the boat is wet under certain conditions as one of the writers points out. The wetness could be minimized without sacrificing the good performance of the boat by a redesign of the first chine or by a more pronounced bow flair. Maybe the hull will be redesigned some day. That would make a very good performing boat a five star performer.
I know Rev 4 props are the best for the boat. One of the best features of the hull is its ability to plane at low speeds. The Rev 4 props pull the boat up big rollers at slow speeds without cavitating. Often the boat will run drier if the planing speed is reduced.
Other things I find that reduce wetness are using the trim to raise one side of the boat when quartering into heavy seas. Triming the engines out raises the bow, reducing the spray but causing a deteroration in the ride and making the boat run less efficiently.
The boat rides drier if it is up on plane rather than mushing along at displacement speed.
Can I make my 305 run as dry as my 23 Conquest...no way. The spray curtains stay on winter and summer.
The Verado guru Glen e has the best advice for engine height. I do point out that raising or lowering the engine has nothing to do with lightening the bow.
revsrobson posted 02-28-2008 08:51 PM ET (US)
I definitely think the 305 Conquest has factory installed 250 Verados that would benefit from raising the engines 1 hole which is 3/4 of an inch. Right now the cavitation plate on the outside of the engines is 3/4 of an inch BELOW the hull. It is about even with the hull on the inside. This setup blasts spray forward when the boat is at cruise with the effect of having the whole back of the boat up to the rear boarding door covered with salt deposits after a day of cruising. That is simply not right.
I think Glen e is right on when he said that Whaler buries the Verados on that boat and the boat would benefit from raising the engines and would really benefit if Mercury made a 15p Rev4 hopefully with Enertia metal. Now that would be a prop!!!!
Regarding the controversy of the 305 being bow heavy I have a couple of comments. Most of the boats I have owned in my life have more weight at the stern. Consequently they are usually lower at the stern at rest and if it is a heavy boat, need trim tabs to bring the bow down. This is not the case with the 305 Conquest. I would characterize the 305 as being "neutral" weight-wise with most of the weight amidships. This gives the impression of the bow being too heavy compared to most boats. This is a disadvantage in very rough seas ( say 6 footers) where it would be helpful to be able to get the bow further out of the water to not only create a more comfortable ride but help to keep the salt spray off of the topsides. You CAN'T get the bow high enough on a 305 when it is rough like you can on other boats because so much of the weight is forward of the transom.
The other big issue which is directly related to the heavy weight amidships is the ridiculous lack of flair in the bow to stop the bow from burying itself into a wave at slow speeds. I have lost count of the number of times that I have spent hours polishing the boat and as soon as I leave the dock I am confronted with another boat's giant wake. If I bash through the wake fast I end up spraying salt all over the windshield. If you don't want to do that, the prudent thing to do on most boats is to slow right down and let the waves pass under you. On most boats this is no problem. On a 305 Conquest, if the wake is big enough, after the 2nd or 3rd wave the Whaler anchor pulpit buries itself right into the wave and you instantly have a salt soaked horn ( which quits functioning a few days later), anchor, windlass, and anchor pulpit. This pisses me off all because their is not enough buoyancy and flair at the bow. This is why I agree with people when thsy say the 305 Conquest is bow heavy. It is bow heavy because 300 gallons of gas are located quite far forward.
One advantage of the 305's weight distribution is that it can handle alot of weight being added to the boat without upsetting the performance or the attitude of the waterline. Fully loaded or empty the waterline doesn't change much. If I had a boat that kept the spray below the rubstrip I would be alot happier.
handn posted 03-01-2008 08:57 AM ET (US)
Revsrobson has got it pretty much right. Going off plane into a big wake invites a soaking. Usually I can escape with only a little bit of spray if I go over the wake at a reduced planing speed.
The only remedy I have for frequent boat cleanings is to boat in Mexico where there is someone waiting at the dock for you happy to clean the boat at a reasonable price.
Every hundred hours I take the top part of my winch apart, clean the old grease off and coat everything with marine grease. I forgot last time and had great difficulty taking the winch apart as everything had corroded together.
My horn has never failed. Yours must be leaking salt water somewhere. I am replacing my navigation lights as the starboard one has sprung a leak and shorts out at the first good soaking. The port one is o.k. but they only sell them in pairs.
Is there a budding small boat designer out there. Someone more talented than I out there could design after market spray rails and sell them like hotcakes. There are a lot of wet 305 owners out here.
My friends Albamarle 26 handled badly and was wet as a submarine. Both characteristics were much improved by factory designed spray rails. The early Cabo 31's were soaking wet much to the disgust ot their fat walleted owners. The factory listened to their complaints and designed spray rails.
Ricky posted 03-01-2008 01:54 PM ET (US)
Seems there are a few people with my issue. Before my 305, I had a 1989 25 foot Revenge that I wore two sets of engines out on. Never a drop a water over the bow. (Maybe you did not notice because of the pounding you took). None the less, the 305 is a great boat but could be almost perfect if Taco Marine or someone designed a spray rail and attached it to existing rub rail fasteners. I'm not smart enough to figure that one out.
Wanted to do this post because didn't want others thinkng boat is a loser. Very nice when you are half way to Bahamas knowing this boat is under you. We all want perfection.
revsrobson posted 03-07-2008 02:01 PM ET (US)
I agree with Ricky, the 305 Conquest is a GREAT boat. Sure it has a major deficiency in that the boat is "wet" in rough seas, BUT you feel REALLY SAFE in this boat when the waves get big. I also think the 305 styling is way above the competition and the Verados are awesome. I would like to get a bigger boat but frankly I don't care for the 345 Conquest (especially for $200,000 difference!!!!) and the other choice I would consider, a Tiara 3500 Sovran is way too expensive for me. I think I will stick with my 305. It will take me anywhere I need to go.
JIGS posted 03-10-2008 02:09 AM ET (US)
I have a 2005: 305 Conquest and have fully raised both engines. The Pros: I have noticed speed increases of about 3-4 extra MPH's and also marginally gas consumption savings. The Cons: in rough waters I have lost some noticeable handling characteristics, in order to combat that I have to keep the engines trimmed down.
I would not consider the bow of the 305 to be heavy; I would consider it to be neutrally buoyant. But I agree with handn and revsrobson, the 305 is a wet ride and the nose will burry itself into a wave especially in low speeds.
My navigational lights are also always giving me problems, probably from the salt spray, (the perko lights are not water proof). I usually fix the situation by unscrewing the top and moving the bulb to get a better contact also bending the top holder for the bulb gives it better contact and that solves the problem for some time.
revsrobson posted 03-10-2008 11:35 AM ET (US)
Questions for JIGS. I am planning to raise the engines on my 305 as well so I would like to ask you some detailed questions about your experience if you don't mind.
When you say that you "fully raised" your engines, do you mean that you raised them as far as possible i.e. 2 holes from the factory setting of the middle position, or did you only raise them one hole?
When you say negative handling characteristics in rough water, what exactly do you mean.
Lastly I would like to know what props you are using. Are you still using the Mirage props? What engines do you have? Thanks for your time.
Tohsgib posted 03-10-2008 12:43 PM ET (US)
They make universal spray rails that will work for your boats. Friend had a 15' Palmbeach and it would literally soak you...literally. We put a set of these spray rails on(3m glue) and it was 75% better which meant you only got wet and not down to your skivies wet.
JIGS posted 03-11-2008 12:22 AM ET (US)

Dear revsrobson:
1. Yes, when I said fully raised the engines I mean 2 holes from the factory mid setting. In retrospect I probably should have only raised them one hole at a time and checked their response. But my boat is full time in the water and it is difficult for me to have the dealer make those kinds of changes.
2. What I meant about the negative handling in rough weather. My best description is that the boat feels like it skids over the water instead of plowing thru it especially when making any turns. In other words, one of the most impressive handling characteristics my 305 had was the sharp turns (even a 360) that one could make even at full speed; it felt like the boat was on rails. Now the boat skids a little in clam waters and more in rough conditions than what it used to. Therefore, because of the skidding the boat feels a little looser and it takes a little longer to react. Probably not noticeable to a non Whaler owner because it still handles better than most other boats. I hope that explanation helps.
3. I have 250 Verados with the 2005 factory props: Mercury Marine Mirage Plus; 3 bladed model No's: 48-19841 15 P (port); 48-19838 15 P (starboard).
Does anyone have any recommendations for better props in which the extra performance enhancement would make it worth the extra expense?
I've heard the Mercury reps say the engines should be revd. between 6200 & 6500 RPM's at full throttle but the max my engines rev is about 5800 for my port and 6000 starboard. What results for the max RPM’s are you getting?
In addition, I've never gotten the results stated in the engine performance test provided by BW. I am usually off by 2 to 3 MPH's in the speed ranges and I've never gotten to 1.35 mpg; at best I've been at 1.15 mpg at cruising speed and usually 1 mpg. Mind you, my boat has all the extras including the Genset, A/C, Toys, and ect. What performance results are you experiencing?
Thanks for your time.
revsrobson posted 03-11-2008 03:02 AM ET (US)
Thanks for the quick reply JIGS. After reading your description of your boats handling with the engines raised, I am more confused than ever. When you describe the boat skidding out in the turns, I can't even imagine my boat doing that. Are you talking about the outside engine getting too high out of the water on sharp turns and the prop blowing out ( unless you trim the engines down)? The boat doesn't actually skid along the top of the water does it?
I think you should look into changing your prop to an enertia by Mercury. Check out Ken at www.propgods.com
I was hoping that by raising the engines I would gain more RPM's so that I could use a 17P Rev 4 prop but after seeing the RPM's you are getting I am not so sure anymore. My engines perform very close to yours. I get about 5,840 out of my port engine and about 6,070 rpm out of the starboard engine. I have been told that the rev 4 prop will drop the rpm's by at least 200 rpm and maybe as much as 400 rpm. This would drop the port engine below the acceptable minimum of 5,800 rpm.
My gas consumption is very hard to figure out precisely. My Smartcraft guage is not accurate ( in my opinion) when it is on the MPG mode. I have NEVER seen it higher than 1.1 mpg. I believe this is an inaccurately low reading. If I switch the Smartcraft guage to gallons/hour I believe the guage is extremely accurate. At 4,000 rpm I am burning around 20 gallons per hour. From my calculations this works out to 1.3 mpg which is close to Whaler's claim of 1.35 gallons per hour ( which I am sure was accomplished with no bottom paint or hull transducer) The last time I wound my boat out it hit 38.5 knots with a light load.
One last question about raising the engines. Did you notice any less accumulation on the amount of salt spray that accumulates on the engine cowlings and aroumd the transom boarding door area after you raised the engines? I get a lot of spray shooting forward from the engine legs at cruise and after I stop, the back half of the engines are covered in salt. I was hoping by raising the engines, this would be eliminated.
glen e posted 03-11-2008 07:10 AM ET (US)
I am going to say this one more time...We have done this to (2) 305's with 250's down here. Stock mounting by whaler and verados is terrible from the factory.
Do this:
1. run rev 4 17's - period...if you want get them pitched to 16, you would be perfect but 17 will work and get you 5800 if properly trimmed in a prop test. The boat is too big and heavy for enertias..period...
2. Mount on the hole that puts the cav plate getting splashed, but out of the stream
3. yes this will stop the splashing and get you better cruise mpg and much better holeshiot.
call apro on this - ken at propgods....
glen@veradoclub.com
JIGS posted 03-11-2008 11:13 AM ET (US)
revsrobson and glen e: Thanks for the prop info and lead, I look forward to talking with Ken.
The spray is much less now.
I get very simillar performance with you except I've never been able to run at 38.5 knots even when the boat was new, without bottom paint, low weight and wind at my back. My max has been 36.5 knots, not an incredible difference but you mentioned you are bottom painted. What you didnt mention is what props you have on and whether you have the Genset, A/C and other extras which weight down my boat.
As far my boats performance, I live in Miami Fl and Id be willing to meet you in the water and test drive both boats.
revsrobson posted 03-11-2008 12:35 PM ET (US)
Thanks Glen and JIGS. What this boat really needs is a 15P Rev 4 but they don't make a counter-rotating version. Why they don't is beyond me.
My boat has the factory set-up. Engines mounted in the middle hole, standard Mirage props, diesel generator, custom radar arch but no air conditioning. Up where I live, Vancouver British Columbia, you definitely do not need air conditioning. I have an espar diesel heater instead. I try to keep my boat as light as possible so I passed on the all chain rode and have a chain/rope combination and I don't have downriggers etc.
Because we are so far apart I guess we won't be comparing boats anytime soon.
Ricky posted 03-11-2008 03:27 PM ET (US)
I have called Ken. He is going to bring a pair of Rev 4's to try on my boat (Delray Beach) and he can look at the one hole or two question. Said he would like numbers from a 305 anyway. Will let you know results. JIGS- if you feel like participating in this let me know. No date yet but hopefully soon. Ken is on west coast of Fl.
handn posted 03-11-2008 07:14 PM ET (US)
Glen e is correct 17p Rev 4's perform like they are designed for the boat. I have never run Mirages on my 305 but had one on my 23 Conquest. The Mirages wouldn't hold the boat on a low speed plane in heavy seas and were in my opinion unsuitable for anything but a bass or ski boat.
If 17p Mirages won't allow the Verado engines to run over 6000 rpm what is the point of using them? One might as well run the prop that is best for the boat.
My YamaMerc 225 efi 4-strokes run between 5600 and 5700 rpm with 17p Rev 4's. Top speed is 34 knots. With 250 Verados these numbers should be higher, even with Rev 4's.
Ken2 posted 03-12-2008 02:24 PM ET (US)
Well, it looks like were going to run Ricky AND JIGS boats so we'll have info with the motors in the stock position vs with the Engines raised, and the Rev 4's.
Probably run a set of Enertia's too just to see what happens.
JIGS posted 03-12-2008 11:47 PM ET (US)
Dear Ricky: I spoke with Ken today and I'll take you up on your offer. I think it would be great to test both boats; first I could drive up to Delray Beach run the different props on your boat and then drive down to Miami and run the same tests in my boat. Ken mentioned sometime next week as a possible date. I guess we'll wait for him to fill us in on some possible dates. Looking forward to putting all these questions and variables to bed.
Ricky posted 03-13-2008 02:42 PM ET (US)
JIGS- It will be a nice little science project that maybe others could benefit from. Two prop styles and two engine mounting heights. Identical boats. Four sets of data. I sent you an email separately on logisitics suggestion. Hope Ken can make it. It is such an advantage to be able to test $1000 worth of props without having to buy them.
revsrobson posted 03-21-2008 01:00 AM ET (US)
Really looking forward to hearing how these tests go.
Ken2 posted 03-21-2008 07:28 AM ET (US)
Here are the Numbers from Ricky's boat.
I'm sure he will post comments as well.
JIGS boat had engine issues, so he won't get numbers until that gets resolved.
Both Ricky and JIGS were on this boat during the test.
220 Gal of fuel
3 guys
Smooth Conditions
Stock engine Height (middle hole)
Prop RPM Knots MPH Gal/Hr. Miles per Gal
Mirage 4000 23.9 27.5 22.1 1.24
15 4500 26.2 30.2 27.6 1.09
5000 30.4 35.0 38.0 0.92
5500 33.0 38.0 47.6 0.80
5900 37.0 42.6 60.0 0.71

Rev 4000 23.5 27.0 21.8 1.24
17 4500 28.7 33.0 27.0 1.22
5000 33.0 38.0 40.0 0.95
5500 37.0 42.6 57.0 0.75
5700 38.8 44.7 59.9 0.75

Enertia 4000 21.5 24.7 20.5 1.21
17 4500 27.2 31.3 27.8 1.13
5000 31.0 35.7 37.0 0.96
5500 36.3 41.8 43.0 0.97
5900 39.6 45.6 59.9 0.76
Note: Last RPM value was wide open throttle.
The Rev 4's seem to hook up much better throughout the rpm range.
Rev's out performed the Mirage in economy at all speeds.
Little low on rpm, but the motors are buried, once raised, He might get 5900 or so out of it.
If you only run at 36-39kts, the Enertia did pretty well, but low end and midrange didnt feel as nice as the Rev
Ken2 posted 03-21-2008 07:36 AM ET (US)
Tried to straighten it out so its easier to read
Sorry
RPM Knots MPH Gal/Hr Miles per Gal
Mirage 15
4000 23.9 27.5 22.1 1.24
4500 26.2 30.22 7.6 1.09
5000 30.4 35.0 38.0 0.92
5500 33.0 38.0 47.6 0.80
5900 37.0 42.6 60.0 0.71

Rev4 17
4000 23.5 27.0 21.8 1.24
4500 28.7 33.0 27.0 1.22
5000 33.0 38.0 40.0 0.95
5500 37.0 42.6 57.0 0.75
5700 38.8 44.7 59.9 0.75

Enertia 17
4000 21.5 24.7 20.5 1.21
4500 27.2 31.3 27.8 1.13
5000 31.0 35.7 37.0 0.96
5500 36.3 41.8 43.0 0.97
5900 39.6 45.6 59.9 0.76
Note: Last RPM value was wide open throttle.
glen e posted 03-21-2008 09:37 AM ET (US)
nice....told ya the revs were the answer...
Tom W Clark posted 03-21-2008 11:58 AM ET (US)
Ken,
Thanks for the data. Question 1: Did you really try a 15" pitch MIRAGEplus?The numbers you report are consistent with my expectations for a 17" MIRAGEplus i.e., about 200 RPM more than the same pitch Revolution 4. I would expect a MIRAGEplus with two inches less pitch than a Revolution 4 to turn about 500-600 RPM more than the Rev 4.
Question 2: What engine problems did JIGS' Verados suffer?
Ken2 posted 03-21-2008 12:41 PM ET (US)
Yes, The stock props were 15 pitch Mirage Plus.
We had Ricky trimming the motors a little higher then he normaly did. We were running at 4-6 bars trim on the V guages.
At 6000 the Mirages were just about to slip. But speed was still increasing up to that point.
The Mirage 15's are quite a bit larger in diameter then the Rev's. That might have made the rpm a little easier on the Rev's.
I don't get to run the 15's that much, so I don't have comparisons between those two props on many boats.

As for JIGS engine problem. It was a problem with the Verado 2005 motors. The "Thermostate Dump Fitting" was made out of aluminum, which eventually corroded and dumps saltwater inside the cowling. In 2006, they switched to a bronze fitting which fixed the issue.
I guess it was a somewhat common problem, might have been recalled I don't know.
Glen E knew exactly what I was talking about when I described it, I guess the veradoclub guys had found that problem a while back.
Ken2 posted 03-21-2008 12:54 PM ET (US)
Just to add to that. JIGS said he got the best numbers trimmed to that level when the engines were at the original height.
Once he raised the engines, he can't trim that high.
We experimented with trim quite a bit on a very long run in smooth water to see what was giving the best economy numbers. We did this with the Original props and with the Rev's and Enertia's as well.

I also noticed, "my opinion" the engine mount holes in the transom weren't drilled in the right spot.
The engines were mounted in the middle holes. 2 holes above and below the current position.
BUT, you couldn't have mounted the engines any lower if you wanted to. The steering system and everything was as low as it could get to the transom.
With the engine at that height (as low as possible)
I would think the holes should have been drilled so that would be the lowest position i.e. top hole.
Thats just my opinion though, there may be other factors that I didn't notice.
Ricky posted 03-21-2008 01:45 PM ET (US)
Guess I'll be buying some Rev 4's soon. When JIGS boat is fixed will try Rev's on his setup which has engines in highest position. Between Rev 4's and raising engines may have substantial fuel savings. Jigs boat has bottom paint so some adustment may ne needed for that.
Boat has a definate change of "feel" with the Rev 4's. Seemed more stable and seemed to come out of hole better. Purely unscientific comment though.
Asked Ken to give an opinion on engine height with original props. After observing at cruise speeed he said they were clearly mouinted too low.
Also sounds like I better get aluminum dump fitting replaced on my 05 Verados. Haven't had problem yet but maybe because I flush engines each time.
Thanks to Ken from Propgods for arranging test and providing props.
glen e posted 03-21-2008 02:49 PM ET (US)
Ricky - get the t-stat fitting fixed ASAP -flushing has little to do with it - your tech should have done it on your last 100 hour check - we have been warning 2005 owners about this 12 dollar part for over a year now at veradoclub.com:
http://www.veradoclub.com/smf/index.php?topic=92.0
Like I told you guys, there is no question..BW props and mounts the engines wrong on a 305 - never seen one with verados right yet..
revsrobson posted 03-22-2008 01:19 PM ET (US)
Thanks for sharing the test results guys. After hearing Ken's opinion on the engine mounting height, I am definitely raising my engines one hole. I bet that will solve the spray issue and the economy has got to improve with less drag. I am still wondering if the Rev 4's maximum RPM of 5,700 is too low? If you raised the engines one hole it should get up to 5,800 rpm wouldn't it?
Sounds like raising the engines at least one hole and rev 4's are the answer. It will be interesting to see the numbers on jigs boat with the engines raised.
Ricky posted 03-22-2008 02:06 PM ET (US)
It is possible to pound down the Rev 4's to a 16 inch pitch. The cost for doing that is about $80 each according to Ken. Seems like that would be the ultimate solution, along with raising engines one hole. Not sure why you need to get rpm all the way up to spec. Maybe cleans out engine. Not going to spend much time at that speed burning 60 gph!
revsrobson posted 03-22-2008 08:16 PM ET (US)
Thanks for getting everyone the performance stats on the 305 Whaler Ricky. I agree that raising the engines one hole is a must do!! I believe the Verado minimum wide open throttle operating range is 5,800 rpm and maximum is 6,400. The rev 4 turning 5,700 rpm still concerns me. I bet a 15P Rev 4 would be perfect. I would hate to buy two brand new Rev 4's and start pounding on them. I mean have Ken who is the expert pound on them. How successful is taking a brand new 17P rev 4 and pounding it into a 16P Rev 4. Are there any vibration issues when you do that? Is the metal as strong after it has been modified? A lot of people have told me that 5,700 rpm wide open is too low but I am sure raising the engines would turn that into at least 5,800.
glen e posted 03-22-2008 08:42 PM ET (US)
once you raise then you'll be at 5950 -6000 - trust me....
Ken2 posted 03-22-2008 10:48 PM ET (US)
I don't pound on them. I just have them for testing, and for sale.
I deal with a couple good prop shops here in Sarasota/Bradenton. A good prop shop can repitch a prop without screwing it up.
Rich Junker, at Leading Edge Propeller is the guy I normally use. Very custom work, and decent prices.
He can take a 17 Rev 4' or any other prop for that matter, and bend it back to a 16 or 15, and it will be better balanced and more precise pitch when he's done with them, then they are out of the box.
(They can normally go up or down 1 to 2 inches in pitch)
Sometimes when people buy a set from me, they have him balance them, and double check pitch (brand new props) before they even get them.
Mercury, has good quality control, much better than most others... its rare, but not unheard of to get a brand new prop that has a little vibration at a certain rpm or something.
revsrobson posted 03-24-2008 03:26 AM ET (US)
If you can change the pitch on a Rev 4 17P to a 15P, does that mean that if you want Rev 4 15P propellers, can you buy the stock Rev 4 15P and also buy one counter-rotating Rev 4 17P and have it modified into a 15P? Would that be the easiest way to end up with two balanced Rev 4 15P props?
Ken2 posted 03-24-2008 03:41 PM ET (US)

I'd probaby get a matching set of 17's and have them repitched.
But I don't see why you couldn't get a 15 RH, and 17 LH and have them matched up. I'm not an expert on repitching and modifying props though.
glen e posted 03-24-2008 11:55 PM ET (US)
Revs -
a 15 p rev for sale in the trading area on veradoclub
Tom W Clark posted 03-25-2008 08:47 AM ET (US)
No, You don't want to match a 15" RH and a modified 17" LH Revolution 4. They won't be the same.
While propellers can have their pitch altered, you cannot change the root of the blade. The 15" Revolution 4 and the 17" revolution 4 are unique castings. The blade shape can be changed to come degree but where the casting of the blade emerges from the hub is not going to move, only the outer blade is.
It is perfectly reasonable to change pitch by one inch. Changing two inches can be done but you start to loose the benefits of the original design.
There are other ways to gain RPM with a given prop. Blade thinning and reduction of cupping aka "labbing" can increase the maximum RPM a given prop will turn by several hundred RPM, but labbing has costs too and not just money.
For the Conquest 305, the best course of action would be to start with two 17" counter rotating Revolution 4s and modify them to 16" pitch. A good shop will match them up in this process which is important on any twin motor boat. As Ken pints out, not all new props come out the same pitch let alone used ones.
Because the props will be worked on anyway, you may as well buy a set of used 17" Rev 4s and save some dough there.
glen e posted 03-25-2008 12:11 PM ET (US)
good stuff ...thx tom
revsrobson posted 03-26-2008 01:03 AM ET (US)
Yes, thank you Tom. That is good advice. Ken, if you come across any GOOD used 17P Rev 4's let me know. I would like to change them to 16P as per your advice. Thanks
revsrobson posted 04-02-2008 09:09 PM ET (US)
Did Jigs ever get numbers on his boat with the engine raised? It would be interesting to compare with Ricky's numbers.
Ken2 posted 04-10-2008 10:44 PM ET (US)
I hadn't heard from him.
Hopefully the engines are ok.
I'd like to see the difference too.
Ricky posted 04-12-2008 04:49 PM ET (US)
Scheduled test for next week after Jigs gets props from Ken. Will publish after test. Will have to account for bottom paint though. Not sure what effect that will have.
revsrobson posted 04-21-2008 12:27 AM ET (US)
Looking forward to seeing Jigs performance numbers. My boat is still in the backyard but as soon as the weather improves I am raising my engines 1 hole.
The neighbours Bayliner broke the mooring lines in a storm last night and went on the rocks.
Ken2 posted 04-21-2008 05:17 PM ET (US)
I'm just going to post a link to the performance numbers.
Trying to cut and paste from and Excel doc. was a pain the the butt.
http://www.propgods.com/forum/default.aspx?g=posts&m=735˟
glen e posted 04-21-2008 05:40 PM ET (US)
Ken - how did the boat "feel" with the rev 4's...my expereince on this boat, they just feel better... around the dock, in rough water and getting on plane...your opin?
Ricky posted 04-21-2008 09:00 PM ET (US)
Replying to Glen E's post I think Rev 4's were far superior to Mirage from a "feel" standpoint. I had them on my boat and I was present at test in Jigs' boat who had engines raised to bottom hole (highest engine position). Turns and dockside performance were better. Cavitation was an issue with engines trimmed up at certain rpm's. Best answer here I think is to raise Conquest engines one hole (not two) and switch to Rev 4's. My fuel efficiency improved 12% just by installing Rev 4's. If I raised engines one hole it would probably improve more but no data to prove that.
This had been an interesting exercise as the cost to raise engines is about $500 (per my dealer) and props are about $900 (per Internet). You would like to get something tangible for that kind of money and I think the fuel efficiency improvement alone justifies it, but when you add the better handling it starts to look like a great investment.
Another variable in the equation is the extent of trim when running. This has an amazing effect on performance (duh). Hard to exactly quantify even with readout from Verado. With fuel prices where they are a whole discussion on trim may be appropriate.
I had trouble with Ken's link but if anyone wants my spreadsheet showing comparing these results let me know.
JIGS posted 04-22-2008 12:47 AM ET (US)
It was a great experiment in both being able to test two very similar boats with different engine mounting positions and different props. I thank Ken for his professionalism expertise and great all around experience; I could not think of buying any props from anyone else but him and his company which ensures me quality and responsiveness. Props to you Ken (pun intended).
The conclusion Rick and I talked about as the best scenario is to install the Rev 4’s because of the overall control, speed and gas savings and to raise the engines to the second to the bottom hole position (raise them one more hole position to almost the highest engine position). That height should be the right position in order for the engines not to be so buried and at the same time to provide a longer range in trimming scenarios without sacrificing performance.
Rick, for viewing Ken’s link try coping it without the square at the end ;-)
Ken2 posted 04-22-2008 11:19 AM ET (US)
I didn't get to ride on JIGS boat, but when I was on Rickys, the difference in "feel" was very obvious to me.
Some boats are very sensitive to a prop change and some aren't. I've tried everything available on some boats, and the results are all about the same.
That 305 LOVES the Rev 4. On Ricky's boat, those props just held the boat with "authority" and the Mirage and Enertia were spongy feeling. (you'd hit the throttle to test the next rpm, and wait for the boat to catch up to the prop) With the Revs, the boat repsonded instantly.
Certain speeds. like 33kts on Jigs boat went from 49gph to 40gph.
I don't see a 9gph improvement very often. I was suprised.
Tom W Clark posted 04-22-2008 11:40 AM ET (US)
So, do we have a consensus? If using Revolution 4s on the Conquest 305, use the 17" pitch and raise the motors one bolt hole (3/4") form the factory installed position.
Ken,
What are your thoughts on the ultimate desirability of have 17" Rev4s repitched to 16"?
Ken2 posted 04-22-2008 12:51 PM ET (US)
I don't know if its worth it to have them repitched.
JIGS got 5900rpm, which is within specs.
getting them pitched down to 16's would get you to 6100, which would be perfect. Performance and economy would probably be pretty much the same, but it may be a little easier on the engines.
Curious what a verado "tech" would say about 5900rpm WOT.
glen e posted 04-22-2008 08:29 PM ET (US)
5900 would work fine in this situation....tweak em if you want but it's splitting hairs with no appreciable diff..
KCB posted 04-25-2008 12:27 PM ET (US)
I purchased a 2007 305 Conquest in January which is kept in the Keys. Experiencing similar numbers to similarly set up boats (Mirage props, middle hole factory set-up). I greatly appreciate this fine research and will eventually make the recommended changes. You guys are great!
I know this should doesn't apply to the post, but I posted a problem I was having and didn't get much response from 305 owners. I have a bugger of a time fueling my 305. The gas keeps overfilling and shutting off the pump even at slow fill. I understand the integrated vents in the caps. Any real-world solutions?
Ricky posted 04-25-2008 02:00 PM ET (US)
My 05 Conquest has separate vents so I can't help you with gas fill. My only input is that when I first got the boat went on a cruise and ran out of water instantly, after "filling" the tank at my dock. Turns out the water tank does have a vent in the fill nozzel. My garden hose started gushing water all over the place so I assumed it was full. It wasn't. My solution was to take a piece of garden hose with a quick disconnect on one end and just hose on the other and shove it down past the vent. Now works great. (Also found that if you look hard you can see the water level in the tank.)
I know you can't fill gas tanks this way but maybe the concept can be adapted somehow. West Marine sells a funnel with a very long neck that may go down into the tank a ways to get past the vent. Also have seen funnels with long flexible necks. ??????
Thanks for comments about prop test. I learned alot from the experience. Will be buying Rev 4's soon and moving engines up a notch.
KCB posted 04-25-2008 04:44 PM ET (US)
Thanks Ricky for the idea. Maybe someone else with the integrated vents will also chime in.

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