Johnson 88 hp outboard won't rise above 1800 rpm

oconee

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Sep 21, 2010
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I have a 1990 Johnson 88 SPL outboard motor on a pontoon boat. Motor ran fine until the throttle cable broke. We replaced the throttle cable, but the motor now will not run over 1800 rpm's (about 1/3rd of the normal speed). The motor sounds like it has a governor on it because it does not have the deep sound that it had before.

Here is the steps that we took to fix the problem (in the order that we completed them)
1) adjusted the throttle linkage
2) replaced the fuel pump
3) Checked the power pack (the mechanic said that it looked good)
4) Replaced the fuel line and the bulb on the fuel line
5) Replaced the fuel in the gas tank
6) Replaced the stator and the timer base


Motor is still running at a maximum RPM's of 1800. The motor will occasionally reach 3500 RPM's while in neutral, but won't reach more than 1800 RPM's while in forward gear.

Any ideas?

thanks,

John
 

ezeke

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Sep 19, 2003
Messages
12,532
Re: Johnson 88 hp outboard won't rise above 1800 rpm

Take the air silencer cover off the carburetors and look to see that the throttle plates are perfectly horizontal when the control arm is fully forward.

Test compression, then test for spark on the running engine by using an inductive timing light so that you can "read" each cylinder across the range of RPM.
 

boobie

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Nov 5, 2009
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Re: Johnson 88 hp outboard won't rise above 1800 rpm

Check what Ezeke posted above but also make sure your timer base is advancing and the linkage is okay. It could also only be running on 2 cyl's due to bad ignition or fuel probs. Also in your post I didn't see anything about spark plugs.
 

oconee

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Sep 21, 2010
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Re: Johnson 88 hp outboard won't rise above 1800 rpm

Thanks for the response. I will look into it. We have changed the spark plugs.
 

Rick.

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Jul 30, 2006
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3,740
Re: Johnson 88 hp outboard won't rise above 1800 rpm

I'm not familiar with your motor but does it have SLOW mode. Sounds like it may be your problem to me. Anyway, lots of good ideas above to look at. Best of luck.
 

oconee

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Sep 21, 2010
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Re: Johnson 88 hp outboard won't rise above 1800 rpm

We tested compression and spark. Everything was ok. We changed out the spark plugs, but he problem did not improve. We checked the fuel and the linkage, but this did not fix the problem. The motor is still running at 1800 rpm when in forward gear. However, the motor will occasionally rev up to 4000 rpm while in neutral.
Any other ideas?
Thanks for your help.
 

ezeke

Supreme Mariner
Joined
Sep 19, 2003
Messages
12,532
Re: Johnson 88 hp outboard won't rise above 1800 rpm

What was the compression on each cylinder?
What spark plugs are you using?
Did you check spark across the range of RPM with an inductive timing light?
Have you rebuilt the carburetors?
Was timing advancing freely when you moved the control arm forward?
What is the pitch of your propeller? (most pontoon boats use 11 to 13 pitch)
You should not run the engine at high RPM in neutral.
 

steelespike

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Apr 26, 2002
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19,069
Re: Johnson 88 hp outboard won't rise above 1800 rpm

Did you note the condition of the plugs you took out?
 

Sav_Redfish

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Oct 28, 2010
Messages
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Re: Johnson 88 hp outboard won't rise above 1800 rpm

Sounds to me like youre timing is not advancing.
One more thing, did you remove both cables? are they reversed?
Anyway thats my 2cents for what it's worth.
 

emdsapmgr

Supreme Mariner
Joined
Dec 9, 2005
Messages
11,551
Re: Johnson 88 hp outboard won't rise above 1800 rpm

A cylinder may be dropping out when under load. Did you do the timing light test when the engine was under load? It is not good to rev any engine above 2000 rpm in neutral. That engine will rev to 4000 rpm, even if it is only running on 2 cyls-that test does not mean anything. It all comes down to what is happening when the engine is under load. Have you taken a fuel sample to test for water?
 

surrender

Petty Officer 1st Class
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Jan 25, 2009
Messages
393
Re: Johnson 88 hp outboard won't rise above 1800 rpm

3) Checked the power pack (the mechanic said that it looked good)?

Did he test the output with a meter?
 
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