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Prop and motor height question

Posted: Sun Jul 29, 2012 3:37 pm
by Mrtoler
Ok i'm getting tired of the poor performance vie been getting on my boat, I know I'm propped wrong because before my rebuild it would turn 6300 rpms. After the rebuild my boat is alot lighter but I'm not 100% sure my tach is correct now since it started acting funny right before the rebuild, but it will only get about 4300 now at 20mph. Another thing I've been struggling with is not enough weight in the rear and the motor will come out of the water unless I have a couple people sit in the very back when I'm loaded....I have no idea what pitch prop I need or what I have, there is no writhing on mine except where it says shop but that's it....here's some pics of the prop motor height and running in the water at about 18mph

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If I trimmed up this splash got worse

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Re: Prop and motor height question

Posted: Sun Jul 29, 2012 3:44 pm
by timmac
By the pics your motor height looks OK, could go a little higher but not by much, what is your prop pitch and what is your HP and boat length/weight..

Re: Prop and motor height question

Posted: Sun Jul 29, 2012 4:13 pm
by Mrtoler
It's a 24' with 112 johnson 2stroke not sure on the pitch or weight

Re: Prop and motor height question

Posted: Sun Jul 29, 2012 4:35 pm
by timmac
Mrtoler wrote:It's a 24' with 112 johnson 2stroke not sure on the pitch or weight
Start with a new prop 1st, find your pitch/size by some prop experts on here and replace that prop and go from there, adjust height after your new prop, also balance your load on boat, you say its front heavy than store your gear in the back of boat and/or carry more fuel in back.

Whats your top speed now.

Re: Prop and motor height question

Posted: Sun Jul 29, 2012 4:42 pm
by gramps
Ditto on above, I think you can move motor up another notch.

Re: Prop and motor height question

Posted: Sun Jul 29, 2012 5:06 pm
by Bamaman
The motor is all the way down on the transom. The picture from the back side looks like your motor is pretty low.

When it's running at a cruising speed, you should be able to see the anticavitation plate clearly. I just see a bunch of splashing in the pictures.

You might want to move the engine up a notch and see how it performs. I assume that you've got working power trim.

Until you get the engine at the correct height, experimenting with a propeller is a moot effort.

I remember that generation of OMC's to be pretty torquey motors, and 112 hp is plenty to get you up to speed. I don't know what the gear ratio is, but I would think a 13 or 15 pitch prop might work.

Find yourself a good prop shop and get them to tell you the prop's pitch. They can also give good advice. If you remove the prop, you might find a part # with the pitch as the last 2 digits.