correct prop?

boating brad · Jun 9, 2003

i have a 85 13.5ft bayliner capri with a fresh rebuilt 83 evinrude 50hp i also have 15 and 17 pitch props i have tried both with the same amount of weight in the boat, rpm @wot is 4600 and is the same with either prop but the speed with the 15p is 25mph the 17 is 28mph. my question is should'nt this boat be a little faster? or tach up more than that, and if i do get more rpm, will that mean more speed? by the way it does have a doelfin hydrofoil level with the bottom of the transom.

steelespike · Jun 9, 2003

Re: correct prop?

Dont know reccomended wot rpm but I would think that combo would run about 40 mph.5,000-5,500 rpm. Check for wide open throttle,Check compression. The Doel fin will slow top end some but not more than about 2-3 mph.

Spidybot · Jun 9, 2003

Re: correct prop?

If wot is the same with 15 and 17 something is wrong. The 15 theoretically raises rpm at wot by 400 rpm compared to the 17 (200 rpm/inch). Sounds as if the motor itself, not the props, are limiting the rpm to 4600. BTW: Does it sound the same at wot with both? Could be your tach that fools you!

Dhadley · Jun 10, 2003

Re: correct prop?

Something does not add up here. Verify your tach and make sure your motor is running on both cylinders at wot and your sync and link is correct (including timing). Your target rpm is 6000 with an average load. Your boats foam could be full of water so you need to verify the boats weight. Use a shop tach and a test wheel to verify that the engine is indeed able to reach full rpms. That will seperate the motor from the boat and tell you which to look at. Good luck!

duck-n-pond · Jun 10, 2003

Re: correct prop?

Interesting what you say about expected top speed. I just bought a 15' Tempest bowrider E/W a 50hp Force. I can get about 30mph with just me aboard, rpm about 5300. I did hope for faster, but things seem to be working fine. I wonder will you get 40mph with a 50hp?

boating brad · Jun 10, 2003

Re: correct prop?

it could be my tach, the tach seems resposive and ive had it up to 5200rpm and 35mph with just me in the boat. ive also checked the throttle position at wot the cam is giving full throttle, the motor seems to run great, no problem starting or accelerating. foam saturation interesting! i have been thinking of taking it out and making a little storage, but wondering if it will effect the boats boyancy? i take it to santee cooper often and the boat handles great (for its size) in big water, i dont want to compromize that.

iRich · Jun 10, 2003

Re: correct prop?

The foam does nothing unless your boat starts to sink so removing it, (not recommended), would have no effect on the boats handling unless it is waterlogged and therefore adding weight. Rich

Dhadley · Jun 10, 2003

Re: correct prop?

Do the test wheel and shop tach test first. This will tell you if the motor is producing enough power. Why did you have to rebuild the motor? Did it run at higher rpm's before? Good luck!

boating brad · Jun 10, 2003

Re: correct prop?

thanks rich. if i remove any it wont be but maybe 20-30% of it, and probably from the back portionof the boat. if it is saturated foam, my guess is that is where it will be, but i will drill some holes just to make sure. (today) im kinda wondering about the rebuild job on the engine, when i find someone with a pressure guage i think i'll do a compression check. any body know the acceptable compression range? 83 2cyl evinrude 50hp

boating brad · Jun 10, 2003

Re: correct prop?

im sorry, but i forgot to mention that presantly im running about a 30;1 ratio. when i get to 50;1 do you think i'll gain rpm? i now have about 12hrs on the rebuilt motor.

boating brad · Jun 10, 2003

Re: correct prop?

Dhadley, i got the boat as a project about 2yrs ago it had a 85 chrysler 50hp force on it. which was a piece of crap. then i bought a used older model 40hp merc for $400 it broke a ring the first 20min out on the water, so i went with this evinrude 50hp for $1500 because i wanted to fish not work on outboards. im running 30;1 for the break in, and after several hrs (12) the plugs are still clean. so im assuming it is running right. currently i am ready to run the gas out and go to 50;1. and thanx for your input im willing to do anything to get it right

boating brad · Jun 12, 2003

Re: correct prop?

update; after further investigation, i found the little bolt i guess it is a throttle limiter, anyway it was backed all the way out. i hav'nt been getting wot after all. have not put it in the water yet but will after it stops raining guess the guy that rebuilt it wanted to assure that i would'nt over rev it during the break in. maybe that 40mph is in reach

does any body know what max wot rpm would be on this motor? 1983 50hp evinrude (small gearcase)

correct prop?

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