Re: Proper engine height
From what I can see from the pics, the prop wash off the blade is visable and I think I can see the antivent plate. that says that your engine isn't too deep in the water at WOT.
Your comment about backing off I don't think is prop related. I think that is the engine in the "cruise" mode where they keep the timing fully advanced and reduce the butterfly opening in the carbs.
Your rpm's tell me that you are not under propped. The engine will/should be rated 4750 to 5250 or 5000 to 5500 so you are right there in rpm's......at or near the upper limit.
On trimming out and what I see from your pics, a SS prop should help your performance, and may allow you to trim out more before blowout, but selection will be tricky.
Since you should get better performance off it, and be able to trim out more, the boat speed should increase and as a result the rpm's should increase. This should counter the rpm reduction that you should expect by the cupping that SS props usually have which bite the water harder .
So If it were me, I'd be looking for a 3 blade SS of the same dia and pitch as you currently have....optimum suggestion.
I just web searched iboats, Michigan wheel and Merc and didn't find any SS props for your engine as you said.
However, I did find a Michigan prop designed for 74-76 500 Mercs. You might call Michigan wheel and ask them why that prop won't fit your '66 model.
The 10 1/2 x 10 is MWC # 033093
The 10 1/2 x 12 is MWC # 033094
Might give Kenny a holler (Walleyhed) on here and get his opinion as he is the prop expert.
The 10P would give you better hole shot and let your rpm's come up some which may be your best bet. But the SS is a much better performer than aluminum and you might get what you want with the 12P. On pitch, sometimes more is not better. But then if you loose performance with the reduced pitch (10P.......which I doubt) you won't be happy with the setup.
I went to your original input on this thread and you mentioned poorer hole shot and acceleration, but WOT was the same with the CMC.
I think that has been answered correctly by tilt unit dragging in the water at the lower speeds. But you are having to offset more transom weight by the installation of the CMC. The trim will/can help your hole shot and WOT.
You and Kenny will have to decide that, if in fact the MWC SS will fit your engine, whether you would use the 10P or 12P.
Stay in touch and good luck.
Pics were great.
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One final comment. I was running a SS prop of 24" pitch at 5600 rpms WOT. I bought the finest alum I could find (Hustler) but could only get it in 23 pitch (not 24) .
You would think that the WOT rpm's would increase a couple hundred with the 1" drop in pitch. Not So!!!!! My WOT rpms actually dropped to 5000!!!! The difference in performance between the SS and Al overcame that difference......I think the thinner SS blades made the biggest difference as the AL is supposed to be a hot dog for alums.
That is why I said that if the 12P (MWC # 033094) will fit your engine, I think I would be inclined to go with it over the 10P.......my 2c.
Mark
