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Author Topic:   Propeller Advice for Whaler 27
Rick U posted 06-24-2004 11:50 PM ET (US)   Profile for Rick U   Send Email to Rick U  
I am again at the propeller selection stage of my re-power project. The boat is an 1988 Whaler 27 notched transom with new Yamaha 250 HPDI's. Fully loaded including a 55-gallon bait tank and a marlin tower.
Operating range is 4500–5500 RPM.
After breaking the motors in (and replacing a power head) I ran some numbers starting with the props off my old 200's and 2 additional sets my local prop gave me to try.

Yamaha Black Standard Stainless 13.75 x 17
40 26.5 18.9 ? 1.4
42 29.7 22.5 1.32
45 32.0 24.5 1.31
50 37.0
58 43.8

Mirage Plus 15 x 17
40 29.3 24 1.22
42 32.0 25.7 1.25
45 34.5 28.2 1.22
50 38.1 37.5 1.02

Mercury Vengeance 14.5 x 17
40 29.3 23.5 1.25
42 32.5 25.4 1.28
45 35 27.5 1.27
50 38.7 33.5 1.16
52 39.0 35.00 1.11

Looks like the first set is giving me the best economy and the best top speed. Here is my dilemma. The Yamaha props appear to be a little small because I can exceed the recommended RPM. The prop guy doesn't have any loaners between the Vengeance and my old Yamaha propellers. That means I would have to order and have to keep anything else I want to try. Is it worth trying to better the Yamaha's? Can I adjust the throttle stops to keep from going too high in the RPM? Top speed is not that important to me. Also, I like the finish and the hubs much better on the Merc props.

Peter posted 06-25-2004 08:25 AM ET (US)     Profile for Peter  Send Email to Peter     
Rick -- The 13 3/4 x 17s Yamaha props are clearly not getting as good a bite as either the Mirage (the one I have is a 15 1/2 x 17 not a 15 x 17) or Vengence. That isn't to be unexpected given the diameters are small. Assuming the pitch is the same on all props, you should expect the Mirage to get the best traction followed by the Vengence and the Yamaha props and based on your data that is what is happening.

I would think that your 250s should be able to twist the 17P Mirages close to 5500. I have read many times that the Mirage is a speed prop and believe it should be run closer to the surface so I wonder whether they are being run too deep on your boat. Through what hole are your motors mounted (alternatively what is the height of the AV plates relative to the bottom)? Also, what is the on-center spacing between the motors and what amount of toe-in are you running?

In about a week, I will be trying a pair 15 1/2 x 17P Mirage Plus on my 27 Whaler WD pushed by a pair of 225 Evinrude Fichts. So far I've run 14 3/4 x 19P Vipers and 15 x 17P SSTs. The Vipers yield a top speed of about 45 MPH at ~ 5600 RPM and the SSTs yield a top speed of about 43 MPH at ~6000 or higher (I think the motors may be hitting the rev limiters). Best average efficiency (~1.35 MPG) comes at a cruise of around 32 to 33 MPH with either propeller. The 17P propeller is the better choice for me as it allows the engines to turn up to the higher end of the WOT range which is important for the health of the Evinrudes from what I understand. The 17P SSTs, however, do not seem to be getting terribly good grip and I suspect that is because they are not being run deep enough. Hopefully, the Mirages will be the perfect fit.

As cruising fuel economy and good grip in rough seas should be the goals for the 27, in your case you should consider trying Yamaha's 15 1/4 x 17P Saltwater Series propellers. It is designed to be most efficient at cruise (3500 to 4500 RPM through a 1.81:1 gearcase). I had one on my Revenge 22 with a 225 Yamaha and thought it was quite good. Alternatively, if your motors are set deep, you might try a pair of Yamaha black painted steel in the 13 3/4 x 19P size. That should get your WOT engine speed down to 5500 RPM or so. However, if you look at the Yamaha performance reports for boats in the size range of the 27 Whaler, you will see that they are usually running larger diameter propellers in the 15 inch range and most of the time its the SWS propeller.

Rick U posted 06-25-2004 10:06 AM ET (US)     Profile for Rick U  Send Email to Rick U     
Priceless information Peter, thank you. My cavitation plates are at the keel height and the motors are 26.5 inches apart on center. Toe in? (tie bar slightly longer than 26.5) crossing wakes about 40 feet behind the boat at about 35 MPH. Why are the Yamaha's giving me the best economy if they are too small?
Backlash posted 06-25-2004 11:24 AM ET (US)     Profile for Backlash  Send Email to Backlash     

Excellent advice by Peter. The only comment I might make, and I am certainly no prop expert, is that your motors are mounted too low for the Mirage Plus props to perform properly. The Yamaha props are standard "elephant ear" (to quote LHG) props that are made to run completely submerged. They will also slip. Performance props (Mirage Plus, Offshore, Laser II, Revolution 4) are designed to run closer to the water surface or even piercing the water surface and do not slip. I think this is why the Yamaha props seem to give the best performance in your initial tests.

Using the Mercury prop selector, it appears the Revolution 4 might be a good all-around prop for your boat. The prop selector requires "tuning" to best match your application. Be sure to change the gear ratio to 1.81. Perhaps some of our prop experts can help you in fine-tuning it.

Good luck and keep us posted,


Rick U posted 06-25-2004 11:59 AM ET (US)     Profile for Rick U  Send Email to Rick U     
How high are your motors?
Peter posted 06-25-2004 05:23 PM ET (US)     Profile for Peter  Send Email to Peter     
Rick, my motors are 30 inches apart and the tie-bar is 29 3/4 inches long with about a 1/8 inch of adjustment on either side of that. If your tie-bar is longer than on-center distance, then it sounds like you are running a toe-out alignment rather than a toe-in alignment. I don't know what the specifications are for the 27 without the WD but with the WD, Whaler specifies 32 inches on-center and 1/2 to 3/4 inches of toe-in (distance between front of gearcases should be 1/2 to 3/4 inches less than the distance between the center of the prop shafts). I'm not sure exactly what is ment by "crossing wakes" but the general consenus is that it should happen about 75 feet back. All I know is that when I got my boat, the motors were aligned toe-out, the wake was a mess and not far behind the boat, and it was generally noisy because the prop wash from each of the motors was running into each other causing the wash with the exhaust to surface close to the boat.

The engines are mounted (one hole up) so that the middle (between left and ride sides) of the anti-vent plate is basically even with the bottom of the boat (15 inches to either side of the keel). If your AV plates are even with the keel (I'm not sure that is possible with twin motors 26.5 on center), then it sounds like they could be mounted too low.

Rick U posted 06-26-2004 10:56 AM ET (US)     Profile for Rick U  Send Email to Rick U     
I want to try running a true toe in but if I cut my tie bar and don’t like the results, I’m stuck. Where did you get the specs for toe in for the 27 WD? I don’t see anything in my boats owners’ manual. Thanks again
Peter posted 06-26-2004 11:48 AM ET (US)     Profile for Peter  Send Email to Peter     
Specs came from Chuck Bennett and were later confirmed by Dealer Service/Technical Bulletin No.: 4-87. You might do well to contact Whaler to get the specs for the non-WD version. While it is likely that the on-center distance is specified differently, I doubt that the specs called for a toe-out alignment on the notched version as the norm for V-bottom boats is neutral to toe-in with the reason being that water coming off the vee is being pushed outward away from the keel so aligning with a toe-in alignment puts the gearcase more in-line with the flow coming off the boat. Toe-out would put the gearcase more perpendicular to the flow increasing the chance of blow out. Toe-out is sometimes used on boats with long set-back brackets (LHG's boat for example) where the gear cases are set off from the transom by 2 to 3 feet. I think the reason is that at that point the water flow in the wake is tending to curve back towards center so toe-out puts the gear cases more in-line with that flow.

My bar was 30 1/4 inches long from eye to eye centers and the toe-out alignment was about 1/2 inch. Figuring that 30 1/4 inches provided about a 1/2 inch toe-out, I cut the bar and the sleeve that fits over the bar down to 29 3/4 for an approximate 1/2 inch toe-in. The bar can be adjusted from about 29 5/8 to 29 7/8. I still don't know if I have it optimized yet but the wake and prop wash look much better than before the surgery. Worst case is if you cut the bar too much you'll need to get a new bar. General alignment is best done with the boat out of the water. Fine tuning can be done in.

When fine tuning alignment, its best to have water pressure gauges to make sure that neither engine is running dry under any given alignment.

jimh posted 06-26-2004 12:27 PM ET (US)     Profile for jimh  Send Email to jimh     
[Tabular reformat]
jimh posted 06-26-2004 12:31 PM ET (US)     Profile for jimh  Send Email to jimh     
[Tabular reformat]
Rick U posted 06-26-2004 11:45 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Did you contact Cheuck through Whaler's site?
Backlash posted 06-27-2004 08:31 AM ET (US)     Profile for Backlash  Send Email to Backlash     
Chuck Bennett -
Rick U posted 06-27-2004 11:23 AM ET (US)     Profile for Rick U  Send Email to Rick U     
I'll post the specs for reference when I here back from Chuck.
Peter posted 06-27-2004 08:54 PM ET (US)     Profile for Peter  Send Email to Peter     
If the specs are toe-in, take a picture of the wake at your normal cruising speed before you adjust and then after so you can compare.
Rick U posted 06-29-2004 12:44 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Hi Rick,

Toe in: Measure the distance between prop centers and forward edge of the gearcase at the ventilation plates.
The measurement at the forward edge of the gearcase it to be 1/2" to 3/4" less than the prop center measurement.

Chuck Bennett
Boston Whaler Inc.

Peter posted 06-29-2004 03:07 PM ET (US)     Profile for Peter  Send Email to Peter     
That toe-in specification is the same as it is on the Whaler Drive. I think it's a pretty standard specification for most vee hulls.

As a reminder, the measurement should be made with the motors in the down position so that the AV plates are parallel or in line with the bottom of the boat. That's very hard to do if the boat is in the water.

Rick U posted 06-29-2004 03:52 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Are you saying the AV plates should be inline with the bottom of the hull (where they line up)or the lowest part of the hull?
Peter posted 06-29-2004 04:19 PM ET (US)     Profile for Peter  Send Email to Peter     
If you want to be somewhat precise about it, take a 4 foot level or something straight like that, put part of it flush with the bottom of the boat so you have a straight line extending from the bottom of the boat past the transom and then set the trim on the motors so that the AV plates are parallel to that line. Then take your toe in/out measurement.

For engine height, the center of the AV plate should be about in line with the top of the level extending from where the AV plate lines up with the transom (basically the on-center distance). What that means is the outer halves of the AV plates are below the bottom of the boat and the inner halves are above the bottom of the boat when looking toward the transom at the AV plate level.

Rick U posted 06-29-2004 10:42 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Okay, the height looks about right (I had to jump in the water to see but it’s faster and cheaper than a haul out) My motors are currently toe out about ½”. These props are on loan for testing and I need to get them back ASAP. Do you have any creative ideas for getting good measurements with the boat in the water? (I’d rater stay on the dock)
Peter posted 06-30-2004 06:34 AM ET (US)     Profile for Peter  Send Email to Peter     
Assuming that you have the tie-bar type that is connected between the steering arms, measure the length of the tie bar between the eye centers. If the bar length from eye center to eye center as it is currently set is say 26 3/4 inches long and the engines are 26 1/2 apart on-center then the 1/4 inch of over length in the tie-bar appears to be producing a 1/2 inch of toe-out according to your measurement. If you were to cut the bar down by 1/4 inch so its length is 26 1/2 inches, the same as the on-center distance, then in theory if the steering arms are aligned straight, then you should have no toe in or out. If you cut the bar down by 1/2 inch to 26 1/4 inches then it should produce 1/2 inch of toe-in. As the bar usually can be adjusted about 1/8 inch on either side, with an eye-to-eye length of 26 1/8, you should be able to get close to 3/4 inch toe-in. Once you have the bar cut down, you'll need to experiment a bit to determine what length gives you the best handling. Top end performance isn't likely to change much, if any.
Rick U posted 06-30-2004 11:37 AM ET (US)     Profile for Rick U  Send Email to Rick U     
You Da Man ! One more question. Will the measurements from the prop shafts vs the measurements from the front of the gear cases still be accurate when the motors are tilted up?
Peter posted 06-30-2004 12:45 PM ET (US)     Profile for Peter  Send Email to Peter     
Not necessarily. Any slop in the linkages and rubber motor mounts will tend to exagerate the toe-in (or toe-out) measurement when the engines are tilted up because their respective centers of gravity are on opposite sides of their respective pivot axes when the motors are collectively centered and this will cause the motors to turn more towards (or away from) each other. I believe that is why they recommend the measurement with the motors down so that there is no moment about the pivot axis causing the motors to turn relative to each other.
Rick U posted 07-01-2004 04:47 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Okay, this should be fun. I just arranged to borrow a half full tank and a regulator. I’ll try to cut the tie bar and make the toe in adjustment Sunday then run the Vengeance props again. My prop guy thinks the original Yamaha’s are going to be hard to beat.
Peter posted 07-01-2004 11:19 PM ET (US)     Profile for Peter  Send Email to Peter     

I just ran the Mirage Plus 15 1/2 x 17P today and they ran very well, much better than the OMC 15 x 17P or OMC/BRP Viper 14 3/4 x 19P propellers.

Some performance numbers


Peter posted 07-01-2004 11:40 PM ET (US)     Profile for Peter  Send Email to Peter     
Not sure what happened there. Here is the table I was trying to construct when the submit button was somehow pushed.

3500 24 ?? (wasn't checking)
3800 27 1.4
4000 29.5 1.45 (averaged)
4500 33.5 1.4

The Mirage propellers consistently produce at least 0.1 MPG better across the range than the other propellers I've been using. Slip is much lower. The boat's attitude on plane below 30 MPH is much better. The other propellers (shaped somewhat like the Yamaha black steel propeller) seem to be pulling the stern down more causing bow lift.

Rick U posted 07-01-2004 11:46 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Do your Mirage props have vent holes? The ones I tried did not. I'd love to get 1.4 mpg
Peter posted 07-02-2004 08:02 AM ET (US)     Profile for Peter  Send Email to Peter     
One propeller has the PVS system, one doesn't. I bought these propellers on e-bay. The vents on the one prop are closed up. I don't believe they are necessary as the boat steps up on plane without any difficulty because the propellers are not running that deep. If the "hole shot" was improved slightly using the vent system, it wouldn't matter on this boat. They might be more important, however, if the boat was powered by a pair of normally aspirated 4-strokes that need to get the revs up to produce some torque.

Rick U posted 07-04-2004 10:31 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Gave the motors a toe in adjustment today and put the Vengeance props back on. My motors were actually 29 ¾ apart on center. My buddy flaked so I decided not to cut the tie bar without the extra pair of hands. I was able to shorten the adjustment with by tightening the coupler enough to get a measurement of 30” at the prop shafts. The measurement at the front of the gear case was hard to reach, but was a little more than 30”. Wow, what a difference! Those motors are amazingly quiet when they’re not pointing at each other. I gained 500 RPM and 5 MPH for a top speed of 45.3 @ 5500 RPM’s with the wind @ 16 knots + and fully loaded with gas, water and a full 50 gallon bait tank

40 30 22 1.36
42 33.3 24.5 1.36
45 35.6 29 1.23
50 39.7 35.5 1.12
54 43.0 44 0.98
55 45.3

Hopefully tomorrow I’ll get a chance to cut the tie bar and toe out a little further. I’m assuming there is not reason to try the Yamaha black steel props anymore, as they will surely be too little. Thanks for all the help guys, this is fun!

Peter posted 07-05-2004 01:43 PM ET (US)     Profile for Peter  Send Email to Peter     
Based on the prop calculator's slip calculations at WOT, I don't think you are going to do much better than what you have now. If you gained 500 RPM with the Vengence, you should probably gain something on the Mirages as well. I would retry the Mirage 17s and see what happens with those before you make a cut.
Rick U posted 07-05-2004 05:04 PM ET (US)     Profile for Rick U  Send Email to Rick U     
The Mirage Plus props look to have more blade area than the Vengeance and ran a little less fuel-efficient when compared at the toe out setting. Do you think that would remain constant now that I’m running a toe in alignment?
Peter posted 07-05-2004 09:08 PM ET (US)     Profile for Peter  Send Email to Peter     
Can't really say what will happen but I read your original data as showing the Mirage and Vengence almost even in terms of economy. I think you owe it to yourself to try them again. I would run each in varying conditions from flat water to the biggest seas you can find and then decide which are better overall in terms of handling, economy and speed. I still think that a big, heavy boat like the 27 needs as much blade surface area as it can get either through a large propeller like the Mirage or Yamaha SWS or a somewhat smaller diameter 4 blade propeller like the Revolution.

Rick U posted 07-05-2004 09:30 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Roger that. Following all your advise to the "T"
Rick U posted 07-06-2004 10:07 PM ET (US)     Profile for Rick U  Send Email to Rick U     
Talked to my prop guy today and felt the Vengeance props were probably going to be more fuel-efficient than the Mirage Plus’s. Based on my last numbers, He didn’t think I had a need for bigger blades that can be more drag. I’m pretty happy with the new overall performance and don’t want to dial it in too much for any one thing at the expense of meeting all my needs. Can’t say enough about Tom at AAA propellers and also about Peter and all the help on this forum.

Steve (Backlash) would you believe the Merc prop selector advised using exactly the props I ended up with?

After almost two years and more money than I would have spent had I been better at budgeting, this tub is ready to do some fishing.

Peter posted 07-07-2004 07:40 AM ET (US)     Profile for Peter  Send Email to Peter     
Glad I could be of some help.

As I mentioned them before, if you ever get a chance to try a pair of the 15 1/4 x 17P Yamaha Saltwater Series propellers, do so. They are designed to be most efficient at cruising speeds. They are not "speed" props like the Mirages.

Backlash posted 07-08-2004 08:53 AM ET (US)     Profile for Backlash  Send Email to Backlash     

Glad to see you're getting the 27 dialed in.

My problem with the Mercury prop selector is that it always suggests way too much pitch on the props. The actual props it suggests are right on.

Over the 4th I had an opportunity to try a Mercury Offshore (now called VenSura) 4-blade prop on my 21' Walkaround. The Offshore is very similar to the Revolution 4 only lighter weight for smaller V-6 outboards. I was truly amazed at the increased performance; time to plane, acceleration, and holding power. It felt like I had a new engine! My boat has never performed like this. I would highly recommend trying the Revolution 4's if you have the opportunity.


Rick U posted 07-08-2004 11:31 AM ET (US)     Profile for Rick U  Send Email to Rick U     
I wanted to but it would have been a special order and not returnable. If the opportunity ever presents itself without the obligation, I’ll definitely try a set
LHG posted 07-08-2004 04:21 PM ET (US)     Profile for LHG    
For those interested, Mercury generally recommends running the medium sized vent holes for outboards. Because the Mirage and 4-bladed props are a mainstay for sterndrives also, they come from the factory with solid vent plugs. All of these props should be run elevated to some extent.

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