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My 2004 Whaler 150 Sport has a new prop on the way from Tom Clark.

Its a regular gearcase 60 hp 2 stroke with 1.64 ratio.
Full prop number is 48 73136A40 13P (10-3/8" x 13" Mercury aluminum three blade BlackMax)

I did do some additional testing last Saturday with my tach and taking GPS speeds.
This was with 2 adults, 1 child, and 15 gallons of gas (normal trip for us).
I would guess this is about 1650 lb total weight.

Upriver:
3500rpm = 19.3mph
4000rpm = 23.3mph
5000rpm = 31.1mph
full throttle, about 5500rpm = 34.0mph

Downriver:
full throttle about 5400rpm = 36.7mph

I would love to try 3 different props and choose my favorite, haha, but after a few discussion with Tom, he has recommended a 10-1/2" x 12" Stiletto Triad .
I will update with results when I get it on.

Thanks for the help Tom.

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As always, the best way to find out what propeller works best is to experiment. People are often reluctant to do this because the cost of acquiring propellers is high, but in the end, one only usually needs one propeller and just as propellers can be bought, they can be sold again.

I bought and sold dozens of used propellers when I was trying to figure out what would best on my own boat. It became a sport unto itself.
I should add that borrowing propellers is a great way to experiment at very low cost.

Short of personal experimentation, reviewing the performance data of others with identical boats and motors is very useful too; this is why we like folks who go to the trouble of acquiring accurate test data to share it here with others, so others can learn.

Allan -- Thank you for sharing this data and let us know how the new propeller does. You may be helping the next guy.

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I received the prop and was a able to try it out for an hour or so.

Stiletto Triad 12p
3500rpm = 23.3 mph
4000rpm = 27.3 mph
4500rpm = 31 mph
5000rpm = 34 mph
WOT, 5300rpm = 36.9 mph

The Triad didn't seem to be affected as much by upriver/downriver, or possibly it was just the wind/current difference from last time. As discused below, Trim up/down seemed to also have less effect all together.

I did a few WOT runs by myself (about 160 lbs lighter than above) and maxed out about 37.1mph @ 5300rpm (upriver and downriver). I guess ideally this would hit 5500rpm, especially considering it will get 20°F hotter than now?

I feel the boat does plane out faster, but possibly at a higher speed. We like to cruise at 18-20 mph, and I found the Stiletto a little more difficult to do that than the BlackMax, the bow seemed to be slightly higher no matter what my trim (3200rpm with Stiletto vs 3500 rpm with BlackMax). I didn't feel I could get the bow down like I could with the BlackMax. And I would have to try it, but I worry this loss of adjustment will be bad in choppy waters too.

Motor is still mounted in middle of 5 holes, I wanted to do this in steps. I tried to look for the cavitation plate while planed out, I don't think I could see it. Based on other motor features it should have been close to the top of the water.

I was able to make the prop ventilate a few times in sharp slow turns and when going over small wake I had made. Although going straight I found it could handle more trim up (out). It is possible that it would take so much trim going straight that I didn't realize how much it had when I slowed down, causing ventilation, more testing would be necessary to know for sure. I added what I felt to be a lot of trim and it never ventilated going fast or started purpousing.

Going forward options:
I plan to have the boat for a while, so I would like to get the setup close to ideal.

1. At this point I don't know if I should try to raise the mounting height one hole, hoping this would lower the bow and increase the WOT rpm. Maybe with the engine raised I would not use as much trim and would not ventilate at low speed manuevers.

2. Buy another prop, like the Stiletto Star 11p to try to raise stern (lower bow) and raise rpm. Hope this would not effect WOT speed but calcs show a possible 2 mph loss. Then see how it acts before I adjust motor height.

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Allan -- Thank you for going to the trouble of collecting and sharing that data. This will be very helpful to others in the future, especially those with the 150 Sport 150 Montauk.

Every boat is different and every model of propeller is different. This is a good example of that.

You've already picked up 2 MPH with a simple propeller swap, a 6 percent gain. But unfortunately, you are worried you are not achieving a high enough engine speed at WOT? The WOT range of your motor is 5000-5500 RPM. You are already in the upper half of that so I think it is OK.

The Triad is not offered in any lower pitch than 12" so there is no 11" Triad to try. If there were, your RPM would climb, ceteris paribus, by 400-500 RPM so that wouldn't be a good thing anyway beacase you would then be exceeding the redline.

So now the options include trying the Star, which will offer a great deal of stern lift and will hold your boat on plane at a lower speed. I cannot predict how fast it would be because I have no experience with the 150 Sport, but this recent thread discussing the propping of a Dauntless 13 is interesting:

http://www.whalercentral.com/forum/vi...d_id=16572

The one problem Gary reported with the Star was that, because of its size, there was some annoying prop rattle at certain RPM.

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I am not "worried" about more speed as I am about keeping the setup efficient. I was pessimistically thinking I would only hit 5-5.1k when the GA heat comes. That may or may not be the result. I mentioned the Star 11p only because I was assuming it would only increase WOT by 200 rpm from the Triad 12p (but that also may not be the case) and give me a better plane for low speed cruising.

I don't have the experience to know if raising the motor will lower the bow ride height during low speed cruise. In my imagination it does. Just asking before I spend time. If it matters, bow rise during acceleration does not really seem to be my issue, only bow height/control during cruise. Before I really consider this I may do more testing on my ventilation issue.

Oh, and the only reason I mentioned rpm in the motor height discussion was for an added bonus, please don't take that the wrong way. I am aware you told me you didn't have direct experience with a 150 Sport before I made the purchase, but I feel you have more experience than most, so I am happy to accept more input.

I did look at your linked thread a few weeks ago. That thread has some very helpful information. I found it interesting that Gary knew he desired less bow rise than his aluminum prop, where I thought my stock aluminum provided acceptable bow control/height. I possibly just didn't know what to look for. I did compare his speed and rpm to mine before I even purchased a prop.

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If your motor looses about 10 percent power due to heat and humidity (an extreme case), at the most, you would loose 100-150 RPM.

I mention (as always) all of the details, not because I think you do not already understand, but for the benefit of those following this discussion now, or in the future.

Raising the motor another set of holes might help but if you are suffering some ventilation (not cavitation) in turns now, it would make things worse.

Yes, it may be that the Triad is allowing more trim so when you enter a turn it is trimmed too much for full grip.

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I have taken the boat out several times now, confirming the same pros and cons with going from the factory aluminum to the stainless Stiletto Triad. I have though about going with the 11p Stiletto Star, but I don't want a prop rattle issue and I don't want to risk underpropping.

I am thinking about adding a Doel-fin or SE Sport 300 Hydrofoil to improve sharp turning ventilation issue, gain back my trim sensitivity, and possibly reduce planing back to a lower speed. I don't have experience with either fin, but those two seem to get the best reviews. I know there is a split between people that say it is a bandaid for other problems and people that praise the hydrofoil.

...And based on how high I can trim up during WOT now, I hope to be able to raise the motor one hole if the hydrofoil can help in the turns.

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I just put my Dole Fin back on my 60 Merc after having the motor raised one notch with my Stiletto Star 12 X 11 pitch stainless prop. I wasn't real unhappy with the performance without the fins, but I've now got a much better hole shot (3 seconds or less to plane) and my directional stability at lower planning speeds is much better. I did lose about 100 rpms and 1 mph when I added the fin back in.

Also, the fin helped mitigate the prop rattle to where I most times I don't even notice it.

Gary

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Does the prop rattle you were having sound the same or similar as a misadjusted gear selector cable? When I slightly changed the tilt of my throttle control I could actually spin my prop by hand with the throttle barely in fwd position and I could tell it was wrong.

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No, the cables were adjusted after the new prop was installed (there was an issue of it getting into gear properly with the larger prop). This is more like a shaking at low rpm's. Once I get above 1100 rpms we're good to go. I'm told this is not uncommon with large eared, shallow pitched stainless props; more often on 4 strokes than 2, however.

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Thanks for the update Gary. I'm looking into a permatrim now.

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I installed a Permatrim and it seems to have increased the bow control a lot. It looks like top speed was not effected. Yesterday I hit 39 mph downriver and 34 mph upriver. When the boat is on plane the Permatrim about the same height as the water level. The front is actually splashing water over the top of it, so I think I can get away with raising the engine one hole (I'm still in the middle of the five). I will update once I have completed the height adjustment and tested.