posted 07-16-2007 02:57 PM ET (US)        

The engine on my boat was mounted on the top bolt hole so the anti ventilation plate was under the keel line and it ran like a dog, I had the engine raised, so it is on the 3rd bolt hole from the top with the anti ventilation plate about half an inch above the bottom of the keel and now it runs like a different boat – this has made a huge difference and the boat runs more or less perfectly.

Only problem now is that it runs so well that it hit's the rev limiter at 5600 rpm. Currently I have a Mirage Plus 15.5 x 17 pitch prop which gives a max speed of about 40 mph on trim level number 2 before it hits the rev limiter. My dealer lent me a 15.5 x 19P Mirage Plus prop and it now reaches about 43 mph on trim level 2 (nearly 3) at about 5100 – 5200 rpm. Only problem being with the 19P it struggles a bit to pull me out on a mono ski and it is difficult to hold on the plane at about 16 mph when wakeboarding. When cruising the 19P seems better and runs at about 34 mph at 4000 rpm and it will do near on 40 mph with 3 people in the boat. I guess an 18P Mirage Plus would be ideal but Mercury don’t make one!! I have no idea yet on the difference in economy between both 17P and 19P but guess they must give fairly similar economy.

One dealer recommended I try a Bravo Two prop 14 x 19P – they said this will have faster pick up for a skier as the prop is a smaller diameter – does this make sense? Has anybody tried this prop – can they recommend it? The dealer seemed to think that the Bravo Two is pretty well tested, yet the technical people at Whaler say to stick with the 17P Mirage Plus and back off before hitting the limiter.

The prop I most want to try is a 14 x 18P or 19P Enertia – has anybody tried one of these? It is a very new prop design which is supposed to be excellent, but I think it’s recommended more for bigger boats, but the Dauntless is quite a heavy boat. The Enertia is supposed to run at about 150 rpm higher than the same pitch Mirage Plus. An 18 inch pitch Enertia may just keep below the 5600 rpm rev limiter, if not then I would have to try the 19 inch pitch.

posted 07-16-2007 03:27 PM ET (US)            

You are right, correctly propping a boat is very much a trial and error process.

If the 17" Mirage Plus is not enough and the 19 is too much, I can recommend the 19" VenSura (Offshore) or the 18" Enertia.

I run 19" Mirage Plus's on my boat and tried a pair of 19" Enertia's for a while last month. The Enertia is an excellent propeller that will yield an extra 250 RPM compared to the same pitch Mirage Plus thus I suspect the 18" would put you right where you want to be, butmaybe the 19" would be the better fit.

The Enertia also grips very well ventilating less than the Mirage Plus. It will be excellent for water sports.

posted 07-16-2007 05:21 PM ET (US)            

Thanks a lot for the reply.

Sounds like I need to try the 19P VenSura - that should stay at just below the 5600 limiter based on it reving 400 rpm higher than the 19P Mirage Plus. Do you think top speed will stay around 42 / 43 mph or will it drop a bit due the prop being a four blade? Sounds like a great prop for watersports.

What boat and engines do you have, sounds like an outrage. If so, the Enertia should suit a heavier boat like an Outrage very well. Have you stuck with the Enertia props? Do you think a 19P Enertia would give similar performance to a 19P VenSura, I guess the Enertia would give a bit more top speed, but a bit less acceleration than the four blade VenSura. If the Enertia gives me better acceleration than the 19P Mirage Plus, then that should do the trick, my boat just needs a bit more kick to pull me out quickly on a mono ski.

One thing I don't understand is if an Enertia is designed to give heavier boats better acceleration, surely for lighter boats the affect will be even greater. Also using the prop selector on the Mercury website, the Mirage Plus doesn't even come up for the parameters I've used for my boat - strange that Whaler recommend it as the best all round prop for the boat - guess they must test quite a few props for the boat before making a recommendation.

posted 07-16-2007 07:34 PM ET (US)            

The Enertia can be used on any boat with V-6 power including your Dauntless. It is a modestly sized propeller that should work well for you.

Don't put too much stock in any propeller selector, even Mercury's. There is no substitute to testing and believe me, Whaler does a lot of testing of their boats to find what works well. But they also have to prop their models for general consumption and not all boaters use their the Whalers in the same way.

My boat is a 25 foot Revenge Walk Through with old twin Mercury 150s, full canvas, RADAR arch and a lot of gear. In other words not a particularly fast boat. I find the 19" Mirage Plus's yield 5500 RPM at WOT which is redline for those motors. The 19" Enertias yielded 5750 RPM and the 19" Offshores (VenSuras) yielded 5900 RPM.

posted 07-17-2007 05:45 PM ET (US)            

Thanks again for all your advice. I will do my best to get hold of an 18P or 19P Enertia and a 19P VenSura and give them all a try and see which works best. I will also try and borrow a 14 x 19P Bravo Two and see what that's like as this seems to be a good tested prop on my particular boat - I guess in theory the Bravo Two should be similar to the Enertia but not as good.

If anybody else reading has tried any of these props hopefully on a 18 foot Dauntless or similar weight Whaler, please let me know your thoughts.

posted 07-17-2007 07:18 PM ET (US)            

I do not know what the hell your dealer is talking about. The Bravo Two is an enormous elephant ear prop that is for the Bravo Two MerCruiser outdrive. It will not fit a 135 OptiMax with its diameters of 16-1/4" to 20". There is no such thing as a 14" x 19" Bravo Two propeller. I rather suspect the dealer is referring to a Laser II which is made in the 14" x 19" size.

The other prop worth trying would be the 13-3/4" x 19" Trophy Plus. This is the little brother of the Revolution 4 and should provide outstanding acceleration, grip and handling. You will need the Propeller Seal Ring (part #878421) to use it on your 135 OptiMax.

posted 10-08-2007 02:44 PM ET (US)            

Hope you see this. My dealer has finally lent me a nice shiny new Laser II prop 14x19P to try out, which I will fit tomorrow. At present the prop has the vented plastic holes on the side of the prop - am I better off to swap these with the small black plastic gromets that block the holes? Do you know what difference it would make?

I've been running a 19P Mirage Plus which has been pretty good overall, it lacks a bit of pick up compared to the original 17P Mirage Plus, but it doesn't hit the rev limiter at WOT and the boat does about 42mph (speedo reading) at WOT being approx 5,100 rpm. I don't have a GPS which is a shame as the speed reading would be more accurate with a GPS.

Would you hazard a guess at how the boat will perform with the Laser II prop. Do you think it will plane any quicker or pull out a mono skier any faster? I guess top speed will be a touch more and it will rev a bit higher being a smaller diameter than the Mirage Plus.

posted 10-11-2007 01:58 PM ET (US)            

Top speed was great hitting about 45 mph (speedo reading) at 5,500 rpm with just me on board. With 4 people on board it hit 42 mph max at about 5,100 rpm. I had a 19P Mirage Plus on the boat before and that hit 41/42 mph max at about 5,100 rpm with just me on board. My new prop search all started when the original equipment 17P Mirage Plus kept hitting the rev limiter at WOT at just over 40mph.

The Laser II slipped a bit in corners (think this is called ventilating) compared to the 19P Mirage Plus. Pulling me out on a mono ski the Laser II seemed to have a little less pulling power than the 19P Mirage Plus, but still pulled me out ok (even if I did have to hold my breath for a couple more seconds!). When wakeboarding behind the boat the Laser II seemed to be much easier to hold at around 18 mph wakeboarding speed compared to the Mirage Plus which seemed to be very difficult to hold at a constant 18 mph.

I would still love to try an Enertia and a VenSura prop to see how they compare (I think both would need to be 19P to prevent hitting the rev limiter at WOT). If anbody has any experience with these props on a Dauntless 180 I would love to get your feedback.

Think I'm looking for the impossible, but if I could find a prop that gives me the speed of the Laser II but with better acceleration for mono skiing that would be perfect, but from what I can see you have to go one way or the other, better acceleration will normally = less top speed. If any prop will meet my wish list I guess it could be the Enertia - my dealer is getting some of these in within the next couple of months, so if I can get my hands on a demo I will report back. I guess the VenSura will give much better pulling power for watersports being a four blade, but less top speed.

posted 10-11-2007 02:26 PM ET (US)         

The VenSura will be a little slower top end, but have pulling power and great hull lift, but not hold quite as well at elevated heights. You might want to have both props, one for lightweight top end, and one for pulling power.

posted 10-11-2007 04:06 PM ET (US)            

Will do my best to try out a VenSura - very interested to see how one of those would perform. I'm going to try and get hold of a Enertia prop too as there is a lot of hype about how good these are.

posted 10-11-2007 11:45 PM ET (US)            

Sorry to have missed this thread for a while. Yes, I agree with Larry for the most part, the Laser II is a fast prop for top speed but may leave something to be desired for your needs. Your test data would seem to indicate as much.

You can try the use the small or medium vent plugs but I think will will find it leads to more ventilation and not much more, if any, acceleration since you are not running a four stroke motor.

The VenSura (Offshore) would be a good prop to try. I am not sure how it will perform on your boat but I recently propped a friend's Bertram 25 with twin MerCruisers and they performed very well in the 19" pitch. I have tried the Offshores on my own boat as well as a single Mercury 225 on a 22 foot Mako. Excellent grip and good speed if you can find the right pitch.

Your OptiMax 135 is a smaller motor but it should be able to handle it though you may need to go to a 21" VenSura (Offshore) to keep your RPMs below redline.

I have also tried the Enterias on my own boat in the 19" pitch. The 19" Enertia will turn about 200-250 RPM more than the 19" MIRAGEplus and about 200 RPM less than the 19" VenSura (Offshore).

posted 10-14-2007 09:17 PM ET (US)            

Thanks for your reply, appreciate your feedback. I tried the Laser II today with large vent plugs (don't have any medium or small vent plugs yet) and maybe my mind is playing tricks on me, but the pick up seemed to be a bit better with no sign of any more ventilation when cornering at lower speeds on the plane. Seems strange when most reports I read on these vent plugs say they cause more ventilation on most boats and give poorer acceleration which is why I think I may be imagining they are better.

I didn't get a chance to mono ski behind the boat which will be the real test if the pick up is any better pulling me up on a mono ski. I must say the prop is great for speed with 4 heavy guys on the boat and getting up to 42 mph.

Tom - would you mind giving me your thoughts on the ventilation plugs - I don't quite understand how they work and for my particular boat how would you expect them to perform? Do they perform better on a lighter boat (Dauntless is fairly heavy) or why a four stoke compared to a two stroke like my Optimax. Sorry, lack of knowledge on my behalf, so would really appreciate your views so I can try and understand how they work in a practical scenario on a boat like mine.

Going to do my best to get hold of an Enertia and also a VenSura prop to see how they perform - guess both will be great props. I will post something back on the site when I get a chance to try these props - if anybody has tried either prop on a Dauntless 180 I would love to get your feedback.

posted 10-16-2007 12:13 PM ET (US)            

In theory, ventilation holes allow some exhaust gas to escape the propeller hub and mix with the water surrounding the propeller blades *at slow speed*. Once a boat is on plane the exhaust gases are not able to escape the hub and full water flow is restored around the blades...in theory.

The idea with the Mercury PVS system of vent plugs, is that you can select the size of vent hole that works best for your application, or none at all. It is a simple and effective way to offer nearly unlimited ventilation options.

It should be noted that you can mix and match any number or size of vent plug you like. The combinations and permutations becomes quite extensive.

The reason why you might want some ventilation around your propeller (normally we try very hard to eliminate ventilation) is that a mixture of water and gas is softer than the water and a propeller blade can move through it more easily. This has two effects:

- Because it takes less force to move the blade, the motor is allows to accelerate faster that is, it can gain RPM faster. This is where the benefit of controlled ventilation comes in; some motors do not generate much torque at lower RPMs so by allowing the motor to spool up quickly, torque can be gained much faster and the boat may accelerate more rapidly. Once the boat is on plane, ventilation goes away and you get the full benefit of your propeller's efficiency.

But:

- The blade is moving faster but also moving through a medium that is "softer" and thus less forward motion is generated for any given movement of a blade.

All of this is great...in theory, but in the real worked it can break down. For starters, most two stroke outboard son Whalers have no trouble accelerating. If a Whaler is somewhat underpowered, there may be a benefit to controlled ventilation and thus faster engine speed acceleration.

But ventilation also equates to prop slip, the loss of efficiency of a propeller's forward motion relative to it rotation. Think of it like the "featehring" of a clutch in your car or truck. If you are on the launch ramp retrieving your boat with a manual transmission in your car or truck, you really need to feather the clutch and allow some clutch slip in order for your car or truck's engine to gain RPM and pull you up the ramp at slow speed. Let out the clutch too rapidly, and you stall the engine.

The PVS vent plugs sort of allow you to "feather" you prop at slow speed but not at high speed. The PVS vent plugs break down when they ventilate at planing speeds or allow too many RPM during the boat's acceleration thus slowing the time to plane.

If you read the link Larry has provided above, Mercury makes it sound as if the PVS vent plugs alone will compensate for any special situation you may encounter. This is not so. They can only do so much. If the PVS vent plugs really did all that Mercury claims they do, there would not be any need for so many different types of propellers. There would only be one propeller made and we would all just fine tune that one prop with different vent plugs. Not gonna happen.

posted 10-19-2007 09:21 AM ET (US)            

Thanks a lot for your feedback. I understand now why the vent plugs work better for a four stoke as they have less torque than a two stroke, so should be beneficial on a four stroke to get the revs up higer into the power band more quickly with the use of the PVS plugs. Guess they will also make a bit of difference with a two stoke like mine, but not as much difference as they should make with a four stroke.

I'm going to try all the vent plug sizes with the Laser II prop and see how they vary. I will also do my best to try out a VenSura prop and a Enertia prop and report back on here my findings.

As you say Tom the whole process is very much trial and error. Every boat/engine/type of use combination is going to react differently to different props and the best way to get your perfect prop is to try them all. Ideally for my boat you want the lowest pitch possible for acceleration, but a pitch that will sit just below the rev limiter flat out with one person on board, which unfortunately the standard fit 17P Mirage Plus doesn't do!

I'm asking for the impossible a bit, as I want great top speed which the Laser II gives, but acceleration and grip for waterskiing and wakeboarding which the Laser II will struggle with - something like the VenSura will fit that bill better. Ideally I should just bolt a 175 Optimax (same block & weight as 135 optimax) on the back - that would be fun!

Seems to be very little info on this site about the Dauntless range. If anybody reading has a 180 Dauntless and has any feedback regarding props I would love to hear your thoughts.

posted 10-19-2007 09:46 AM ET (US)            

These is quite a bit of information on the Dauntless 180 on this site. Have you used the search engine? I just typed in Dauntless, 180, OptiMax, 135 and propeller and found 37 different threads discussing propellers for your boat.

posted 10-20-2007 12:02 PM ET (US)            

I do seem to hear much better reports about the small tube (intermediate gear care) High Fives on Montauks and other small boats than I do on the large tube (V-6) High Fives on larger boats like 25.

posted 10-24-2007 05:00 PM ET (US)            

Thanks a lot for your feedback. Sounds like a case of every boat will have a different effect with different props. Only way to find out is to try each. I've seen a few Whalers (22 Dauntless, etc) running the VenSura prop, so maybe they suit recreational whalers like the Dauntless well. I will do my best to try each prop and report back on this site.

posted 10-29-2007 10:28 AM ET (US)            

What is the altitude where you boat?

Could you leave a couple of friends ashore or try a bigger ski? :)