2003 90 HP Johnson prop question

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dukboat

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I have a 2003 Johnson 90 HP 2 stroke on a 19 ft CC. I'm running a 14" dia x 17 pitch alum prop, only getting 4500 RPM at WOT. I can get a good used 13 3/4 diam x 15 pitch for $50 Will this increase my WOT RPM? Thanks for any help.
 

Silvertip

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Re: 2003 90 HP Johnson prop question

That should bring it up close to 5000 rpm. Keep in mind just because the engine is running faster, the boat will not likely increase speed unless it was being lugged severely (which it wasn't in your case). Less pitch means more rpm because the prop is taking a smaller bite on the water.
 

dukboat

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Re: 2003 90 HP Johnson prop question

Thanks, thats what I figured, not looking for more speed just want to get the RPMs up
 

phillnjack2

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Re: 2003 90 HP Johnson prop question

4500 at WOT is killing that engine, you need to be up around 5500 to keep the motor from burning itself out.
4500 sounds very poor for that size prop to be honest, but maybe your boat is very heavy ???
first thing i would do is try a 13x17 prop, the 13 3/4 diameter is what is killing your set up, its too much prop diameter.
to use such a diameter is for inboards, much bigger outboards or very lightweight boats.
you might find that a 13x19 will give you around 5,000 rpm maybe a touch more, but i would first try a 13x17 and see the results.
you do need to get the max possible revs from the engine to get it to be at its most powerfull and best all round performance.

also by getting a 5500 top end you might see a bit more speed due to this one lugging the engine something realy bad.
its not even in the powerband at 4500 rpm.
try finding someone near you who can lend you their prop to try out, if its a 13 spline then have hundreds to choose from as the 3 cylinder engines use the same props as the v4 2 strokes with 13 splines.
once you get the right prop to give you 5500 top end, youl also see a huge difference in holeshot and much lower fuel bill !!!!!
the boat will be better all round for sure.

check how many splines and let us know what you have, you might have the larger 15 spline gearbox, but i doubt it.


phill
 

dukboat

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Re: 2003 90 HP Johnson prop question

13 spline, WOT as per Johnson is 4500 to 5500 its in the owners manual, the boat is heavy and under powered, only bought it because it was a deal, The boat dealer by me is going to give me a few props to try, when I get one close to 5500 I'll buy it. Thanks
 

Bob_VT

Moderator & Unofficial iBoats Historian
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Re: 2003 90 HP Johnson prop question

Is the boat heavy due to being waterlogged? I met a person last week with a 2002 16' Starcraft (near identical to my older one) and he was saying that the waterlogged foam weighed over 800 lbs! Get the boat weighed (look up the specs) and see where you are at.
 

dukboat

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Re: 2003 90 HP Johnson prop question

don't think its waterlogged, It a Triumph 19' was stored indoors and not used very much. Its rated for 150HP max and a 90 is a little small. Right now its running 30 mph {GPS} I'm not worried about speed as its just going to be used in the bay I have a Astro Bass boat if I want to go fast. If I go to a smaller pitch and dia prop is ther a point that you will get to max WOT RPM but the prop is to small to get the boat on plane?
 

danquocky

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I have 2004 blue wave 180c special with 2004 90 hp johnson. My prop is 13 7/8 ? 17 and it does not catch water at 3500 rpm. I'm not sure what is the right size prop for me to use. My boat length is 17.8'long.
 

steelespike

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Your numbers seem pretty good with slip at about 17% a ltitle high but that may be from the relatively low wot rpm.
A 15" prop would surely improve the rpm.The boat should feel more powerful stay on plane with less fiddling,
The motor is actually less stressed if it can rev freely within its rpm range and should feel more powerful.
You might consider a 15" 4 blade. Should improve hole shot further,stay on planer easier,should seem smoother
and respond better around the dock.
With some luck if we can get the slip to 10 or 12% We may be able to maintain wot speed.
Either one of these props should make it feel like a different boat.
 
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ondarvr

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I have 2004 blue wave 180c special with 2004 90 hp johnson. My prop is 13 7/8 ? 17 and it does not catch water at 3500 rpm. I'm not sure what is the right size prop for me to use. My boat length is 17.8'long.

You may want to start your own thread on this, I have a Blue Wave also, the setup can be a little tricky.
 

wil141

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Mar 25, 2017
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i have a Johnson1995 48spl can anyone tell me what the torque is for the prop nut
 
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