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Author Topic:   Propeller Suggestions for 23-Conquest, 225-HP Mercury EFI
mustang7nh posted 05-06-2003 08:51 PM ET (US)   Profile for mustang7nh   Send Email to mustang7nh  
225 EFI Merc 1997-- Currently WOT is 5000-5100 RPM with 3/4 fuel (100 gallons) and two people. I believe the range on this engine is 5000-5800. While I may pick up some RPM when fuel burns off, I was thinking about dropping down in pitch to get closer to 5500-5600. Any thoughts?
Perry posted 05-06-2003 10:10 PM ET (US)     Profile for Perry  Send Email to Perry     
The rule of thumb is 200 rpm gained by decreasing 1" of prop pitch. So going down 2" of pitch would give you an increase of 400 rpm. What size prop is on it now and is it a cupped stainless steel prop?
Sal DiMercurio posted 05-06-2003 11:34 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Hmmmm,...100 gallons of fuel indicates a good size boat, most likely a deep V ocean boat maybe 20 - 23'.
Sounds like he's running a 19 pitch prop & he needs to drop down 3" of pitch to get 5,600 - 5,700 rpms.
Sal
mustang7nh posted 05-07-2003 07:02 AM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
Your good Sal- 23 Conquest. Stock prop SS. There are some numbers stamped on the side of the prop that end with a space and the digits P17. The engine seems to labor a bit until 4000-4200. I like to cruise at 3500 but even though on plane the Merc seems to labor a bit. I was thinking of droping down one level in pitch and freeing it up a bit.
Sal DiMercurio posted 05-07-2003 11:03 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Mustang, 1 level is 2 inches of pitch.
400 more rpms wont hurt.
By any chance, is that engine mounted all the way down on the first holes ?
Could pick up another 100 or so rpms by coming up a hole.
Also, see if you can borrow a 14.25x15 Stiletto, as it will raise the whole boat while on plane allowing less drag while increasing your rpms another 100 .
Sal
Sal DiMercurio posted 05-07-2003 03:55 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
To be honest, I feel there isn't a single outboard application today, to do that boat justic.
My opinion is, it needs a pair of 150s, I say 150s, because they should twist a pair of 14.25 x 19s or 21s & only need to be run at 3,500 rpms or less, giving a 30 mph cruise speed plus giving fantastic fuel economy.
The closer a person gets to over powering their boat, the better the fuel economy.
My experience is, lots of horse power on smaller boats means less strain on the engine or engines, equals the best mpg today.
Sal
lhg posted 05-07-2003 08:13 PM ET (US)     Profile for lhg    
This sounds like a 17" pitch 3 bladed Mirage prop. It could be that a 4 bladed Offshore Performance prop would be a better prop for the boat. They are indicated for heavier boats and give lots of lift to improve performance and hole shot. Top end may suffer 1 or 2 mph.

To determine pitch, run the boat light on fuel, with just one person aboard. The RPM should be close to the 5800 mark. If not, drop down to a 15" pitch.

jimh posted 05-07-2003 10:46 PM ET (US)     Profile for jimh  Send Email to jimh     
[Changed TOPIC; was "Pitch to RPM ratio."]
mustang7nh posted 05-08-2003 07:15 AM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
Thanks for all the advice. The engine is a XXL shaft and is long longest shaft I have ever seen. I haven't gotten a chance to play much with it yet but I agree the twins would be more ideal.

But pre-owned I don't have as many options, the price was right, and it was immaculate and barely used by an older doctor. So I'm happy so far with the package with the exception that the hardtop EFI combo is noisy and performance is mediocre.

Hopefully through prop change etc I can get a comfortable cruise speed. I'm not as concerned with top end with this application. I would just like it to purr more at 3500 and not groan (a little exaggeration), even with full fuel and two adults.

But I also hypothesize that the rpm to planing speed for the single is perhaps the problem and not prop. More specifically, the transition from displacement to semi disp to planing takes place as increases in vessel speed. The problem might be that at 3300 rpm with a single screw, the engine can't push the boat fast enough to achieve the more efficient true planing dynamic and I might be in a quasi semi displacement phase. yet once the engine winds out to 4000 the boat has hit enough speed to be fully planed and hence she begins to purr as the load is reduced and efficiency is optimal.

None the less, does anyone know how one goes about trying different props without having to buy them all and keep them?

As far as mounting heights, it is sad that the factory would not mount it properly (if this be the case) particularly in a prepackaged rig.

Thanks again to all.

lhg posted 05-08-2003 03:20 PM ET (US)     Profile for lhg    
Since the 23 Conquest is a pretty heavy boat, you are definitely minimally powered at 225, and could be under-propped as well. Back then, BW had some incorrect weight listing on it's models, and this could have an effect on the prop supplied with the engine. Going down in pitch may solve your performance problem, but not the engine sound problem, since RPM's at a given speed will now be higher.

Like some others here, I believe under-powering is a serious mistake, and greatly decreases the enjoyment of a Whaler.
I would seriously consider looking for a similar year, matching counter rotating, used, Merc 225 EFI and set the boat up with twins. These are available, and for not too much money. The boat will handle the twin 225's, and this will give quiet cruising speed RPM's and tremendous reserve power for load carrying. Top speed will be significant, but no one says you have to use it. Gas mileage will change but will be insignificant, and your attitude about your investment will improve considerably. Your existing 225 will have to be shortened back to 25" with removal of the 30" XXL extension kit.

mustang7nh posted 05-08-2003 06:51 PM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
lhg- that's a great idea, do you have any idea where I would best locate 97 225 EFI CR? THanks
Sal DiMercurio posted 05-08-2003 07:26 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
With a pair of 225s, your talking one haulin booty Whaler, probably 50 mph or more.
There would be minimal wear & tear on either engine as they would coast at 3,500 rpms pushing you every bit of 30 mph.
I would say, if you could run them between 3,000 & 3,400 rpms, you would probably use the same amount of fuel as you would running the single 225 at 4,200 - 4,500 rpms.
But the odds of finding an xxl 1997 - 225 hp [ 30" shaft ]counter rotator aren't so good .
Sal
mustang7nh posted 05-08-2003 07:40 PM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
Would it ever be ok to mismatch years if they are mechanically similar? Like a 96 and a 97 or 97 and 98? I suppose this would kill resale numbers though if you decided to sell it.
lhg posted 05-08-2003 08:11 PM ET (US)     Profile for lhg    
I think the engines close to your year would work, maybe even have the same decals. I would think anything 1996-2000 would work, and a matching decal set is only about $130.
A Dealer can tell you which year models are a close or identical match. Resale would not be affected. On my own 18 Outrage I have a 1984 and a 1985 Mercury 115.
They are identical engines, even same decals.

Used CR engines can be found, since 25" shaft is very common and often used sets are broken up, with the CR model usually being the hard to sell "orphan". I would look around larger local Mercury dealerships and I'll bet you can find one, or they can locate one for you. Even if a dealer has a "set", they most often will break it up to get rid of the CR model, than they have a standard one left to sell, which is easy.

I recently saw a 1998 used 225 EFI, standard rotation, at a Bass Pro Shop in FL, for $6000. There are a lot of these floating around in FL., but I would only buy a used engine locally.

jimh posted 05-08-2003 09:01 PM ET (US)     Profile for jimh  Send Email to jimh     
I have been noticing that the minimum planing speed for many of these heavier AccuTrack hull models is rather high. They plow along in displacement mode, then suddently jump on plane and go 25-30 MPH with just a small change in throttle.

Look at the results for a 26-foot Boston Whaler that was powered by twin 200-HP engines. At 3000 RPM it is only going 9-MPH. Open up the throttle to 3500 and it jumps to 27-MPH.


I have seen this same trend in other test results.

See table in Reference section article:

http://continuouswave.com/whaler/reference/prop2.html

Sal DiMercurio posted 05-08-2003 09:48 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Yep, that 500 rpms puts her right over the top, but in order to get anything that might resemble decent fuel economy, better keep em 3,500 or less.
Sal
tully_mars posted 05-10-2003 02:14 AM ET (US)     Profile for tully_mars  Send Email to tully_mars     
I see all these numbers going around hypothetically, and thought I would through in some facts.

My 23 Conquest with twin 150's will cruise 24knots and get 1.8 mpg at 3200 rpm. That is the most efficient place for it. With the twin engines I can run on a plane at 17knots for rougher seas. 40 knots is my WOT at 5100rpm (2-3 people and full fuel 125 gallons).

My props indicate by part number are 15.5x17 but if you put my top speed number and rpm, gear ratio etc in the prop calculator that gives a negative slip number. If I change the pitch to 19 I get a 3-5% slip number. But I figure they are 17's because the boat can really jump out of the water when I want it too, and I can plane on 1 engine and run home quite nicely.

Tully Mars

mustang7nh posted 05-11-2003 08:56 PM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
Well I've got a chance to run it for a few days. WOT (5100 rpm) with 3/4 fuel and just me is 32.9 knots. Cruise at 3500 is 24 knots if I remember correctly (I've yet to bring a pen and paper with me). I can bring her down to 3100 and just keep it on plane and do around 19 knots. I can plow somewhat ok up to about 10 knots. Prop is not a Laser, it says something on it but again I've forgotten to write all this stuff down.

Nwt that I've burned off all the winterized oil and am getting used to it, it actually leaps on plane if you hammer the throttle. The EFI has alot better throttle response than my old carb beasts.

Question: when getting from slow to on plane- does it put more wear and tear to nail the throttle to 80% or more and then back it off when it planes off rather than give it 50% and let it slowly climb on plane?

Also, in an application like this is it possible that I'll get better fuel economy at 4000 than 3500 due to it being a bit more free than under load?

Thanks for all the help.

Sal DiMercurio posted 05-11-2003 09:50 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Tang, no problem coming out of the hole at 80% then backing off.
Rememmber one thing, rpms cost money [ fuel wise ].
The two worst rpms to run is wide open & about 2,200 rpms, the best is usually in the low to mid 3,000s.
Once you get over 4,000, you need a fire hose for a fuel line.
Sal
bsmotril posted 05-12-2003 11:24 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
The Conquest 23 is rated for 300HP max. I doubt you want to invest another 15 K for another 225 outboard like the one you have now, which will be way too long in the leg for a twin engine set up. (unless you shorten the gearcase). To work with what you have, the 4 blade Merc offshore prop will help a bit and give you a 2-300 rpm bump over the 17 at any speed and a much better hole shot. Top end will go down a few mph, but who runs wide open in an offshore cuddy boat, right? Your prop now is a Mirage 17. The offshore of the same pitch with four blades will spin a bit faster, I've tried them and know that for a fact.

I run a pair of 17' Mirages with Opti 135s on a Conquest. I get an honest measured 3mpg at 3200 rpm, they hit readline at 5600 rpm and 45mph and will keep the boat on plane down to 18mph and 2800 rpm. I tried the offshore 4 blades at 17", with no noticable impovement other than a better hole shot. The 4 blade comes into its' happy range in a single installation on a big heavy boat, like what you have. With two props on my boat to carry the weight of the rig, the 4 blades did not buy me much. You should be able to find a Merc dealer to loan you one with a deposit for a sea trial. That is what my dealer does. Don't listen to anyone who tells you to go to a smaller diameter high rake prop (stilleto) on this boat, it just does not work. The conquest is a big heavy boat with a high drag hardtop and deep vee. It needs the blade area of a bigger prop to perform like it should, especially with a single engine.
BillS

bsmotril posted 05-12-2003 11:27 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
The Conquest 23 is rated for 300HP max. I doubt you want to invest another 15 K for another 225 outboard like the one you have now, which will be way too long in the leg for a twin engine set up. (unless you shorten the gearcase). To work with what you have, the 4 blade Merc offshore prop will help a bit and give you a 2-300 rpm bump over the 17 at any speed and a much better hole shot. Top end will go down a few mph, but who runs wide open in an offshore cuddy boat, right? Your prop now is a Mirage 17. The offshore of the same pitch with four blades will spin a bit faster, I've tried them and know that for a fact.

I run a pair of 17' Mirages with Opti 135s on a Conquest. I get an honest measured 3mpg at 3200 rpm, they hit readline at 5600 rpm and 45mph and will keep the boat on plane down to 18mph and 2800 rpm. I tried the offshore 4 blades at 17", with no noticable impovement other than a better hole shot. The 4 blade comes into its' happy range in a single installation on a big heavy boat, like what you have. With two props on my boat to carry the weight of the rig, the 4 blades did not buy me much. You should be able to find a Merc dealer to loan you one with a deposit for a sea trial. That is what my dealer does. Don't listen to anyone who tells you to go to a smaller diameter high rake prop (stilleto) on this boat, it just does not work. The conquest is a big heavy boat with a high drag hardtop and deep vee. It needs the blade area of a bigger prop to perform like it should, especially with a single engine.
BillS

JoeyP posted 05-13-2003 10:45 AM ET (US)     Profile for JoeyP  Send Email to JoeyP     
Good info here. I have been thinking about going to the REV 4 props. I'm running a 275 Conquest(formally known as the 26)with twin 200 Opti's. I have the 17" pitch mirage plus props now.

Does anyone know the difference between the four blade offshore and the Revolution 4's?

The New 2003 Conquests powered with the 225 four strokes are propped with the 17" pitch Revolutions 4's.

BW23 posted 05-13-2003 02:26 PM ET (US)     Profile for BW23  Send Email to BW23     
Mustang,
I have the same setup as you. prop is believed to be 14 1/2 x 17, it is a Vengance.

Things to note, When I had the boat surveyed and sea trialed last May, the surveyor was able to obtain a top speed of 38 knots(rpm unknown) documented by GPS (4 people,1/2 tank fuel). Shortly after I purchased it I tried to achieve the same top speed and I was unable to achieve more than 31-32 knots running abot 5100rpm WOT. I tried numerous tilt / trim tab settings with little change.

I contacted the surveyor and he recommended that once I achieve aprox. 4000 rpm I should to trim the motor up to get it to ventilate / cavitate and the rpms will increase of course. Once the rpms increase I can then lower the motor and try to get the prop to "bite" which will enable me to obtain higher rpm's and higher top speed.

Once again I've tried many settings and I will more than likely not switch props. Unless you come up with a good answer.

I rarely run WOT but I would like to duplicate what the surveyor observed. I was present during the sea trial but never tested WOT myself. Other than this I'm quite happy with the boat.

mustang7nh posted 05-14-2003 07:43 AM ET (US)     Profile for mustang7nh  Send Email to mustang7nh     
BW23- yes, my prop is a Vengance also. Sounds like we have similar performance. The idea of getting the engine to rev by ventilating and then trimming down sounds like a speed trick that is not very practical for every day use. Also, probably not very good for the engine. I suppose the theory is that by getting the engine to wind up higher into peak horsepower, you then could reapply the resistance by trimming down and hopefully get the engine to stay reved up and hence more speed.

I might try it once for fun but like you I'll probably stay with the Vengance for a while. The four blade props sound interesting and if I can find a marina that will let me try one I would be interested.

What kind of gph are you getting?

Thanks and take care.

BW23 posted 05-14-2003 08:51 AM ET (US)     Profile for BW23  Send Email to BW23     
Mustang,

I never did any fuel calculations last year.
This off season I insatlled a Standard FF41 fuel flow meter and garmin 2006 C chartplotter.

I'll keep you posted with the numbers.

Dave

diveorfish posted 05-19-2003 12:15 PM ET (US)     Profile for diveorfish  Send Email to diveorfish     
bsmotril: Have you ever considered switching to 19 pitch props? I have the 17 Mirages as well and my numbers are roughly the same as yours. I was wondering if the 19" pitch props would be better for top-end speed and cruising speed economy. On boattest.com they tested a 23 Outrage 19 props and top-end was almost 50mph and most efficient cruising speed was faster with lower RPMS. Right now my hole-shot is almost instantaneous, would it suffer much with 19 props? Do you (or anyone for that matter) know the pros and cons?
andygere posted 05-19-2003 04:02 PM ET (US)     Profile for andygere  Send Email to andygere     
Mustang,
the Mercury 200 on my Outrage 22 Cuddy came set-up with a 5-blade 19 pitch Mercury High Five prop. Even with a T-top and enclosure, 70 gallons of fuel, 3 adults and a lot of gear, the boat hops out of the water fast and did 44 mph in a stiff breeze this weekend. The hole shot and rough water bite on this prop are outstanding, and it may be another option worth considering.
Sal DiMercurio posted 05-19-2003 08:51 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
BW, do "NOT" alow your engine to ventilate [ over rev ] & try to get the prop to catch, as these engines are not designed to run without a load at high rpms, & thats exactly what you would be doing if you allow it to blowout & try to make it catch again.
It's like floor boarding your stick shift truck & popping the clutch.
It is a very bad thing to do to an outboard.
Sal

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