Prop and motor height question

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Mrtoler
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Joined: Wed Jul 21, 2010 8:58 pm

Prop and motor height question

#1 Post by Mrtoler » Sun Jul 29, 2012 3:37 pm

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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Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
2014 South Bay chassis (IN THE WORKS)
2006 dodge ram quad cab
Crosby Texas

timmac
Posts: 123
Joined: Mon Jun 07, 2010 12:02 pm

Re: Prop and motor height question

#2 Post by timmac » Sun Jul 29, 2012 3:44 pm

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..

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Mrtoler
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Re: Prop and motor height question

#3 Post by Mrtoler » Sun Jul 29, 2012 4:13 pm

It's a 24' with 112 johnson 2stroke not sure on the pitch or weight
Ryan, Martha, Ana and Nathan Toler.
(SOLD)1992 24' monark sun spa 240 1996 (rebuilt) Johnson 112
2014 South Bay chassis (IN THE WORKS)
2006 dodge ram quad cab
Crosby Texas

timmac
Posts: 123
Joined: Mon Jun 07, 2010 12:02 pm

Re: Prop and motor height question

#4 Post by timmac » Sun Jul 29, 2012 4:35 pm

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.
Last edited by timmac on Sun Jul 29, 2012 4:59 pm, edited 1 time in total.

gramps
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Joined: Wed Dec 21, 2011 1:47 pm

Re: Prop and motor height question

#5 Post by gramps » Sun Jul 29, 2012 4:42 pm

Ditto on above, I think you can move motor up another notch.
2012 Berkshire, 230cl Tritoon
150hp Mercury 4stroke
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Bamaman
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Location: NW Alabama--Tennessee River

Re: Prop and motor height question

#6 Post by Bamaman » Sun Jul 29, 2012 5:06 pm

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.
'12 Bennington 24' SSLX Yamaha 150

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