'88 Evinrude 90Hp not achieving WOT

jwalt66

Recruit
Joined
Jul 12, 2021
Messages
3
Hello everyone. As the title states, I own an '88 evinrude 90 hp. I recently purchased it about a month ago and have been chasing problems ever since. A few issues that I am having are as follows;
-stall at idle in neutral
-must be started at high idle, even after warmed up
-while underway in forward gear, when I try to go WOT, I can only get 3000 rpm. I took it out today and tried to open it up to full throttle. After a brief run at 4500 rpms, it bogged down to 3000 rpms and stayed that way for the remainder of the run. It would briefly jump up like it was trying to open up but stayed at around 3000 rpms. This is all while the controls are at full throttle.
-idles and runs fine on muffs without any load

Repairs made so far:
-new plugs gapped at .040
-cleaned and rebuilt carbs
-new ignition coils
-new thermostats
-new water pump and impeller
-changed Lower unit oil
-changed fuel water seperater
-new ignition switch


Could any of this be caused by a bad stator, timer base, or regulator? I'm not sure where to start and any information would be greatly appreciated. I'm new to boats and I am learning a lot. Sometimes more then I wanted to! I want to try to make this a reliable running motor so I can go wet some lines, but so far I have only been able to take it out for 2 test runs.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
38,674
Lots of work and guessing done.----But step #1 is a compression test.----Post your values.----These motors are nearly world famous for broken piston rings.
 

jwalt66

Recruit
Joined
Jul 12, 2021
Messages
3
I meant to post that but it got missed.. The compression is 100 psi across all 4 cylinders.
 

jwalt66

Recruit
Joined
Jul 12, 2021
Messages
3
I just went our and checked the compression again. It w
I meant to post that but it got missed.. The compression is 100 psi across all 4 cylinders.

I meant to post that but it got missed.. The compression is 100 psi across all 4 cylinders.
These are the corrected values for the compression check 100-90-89-80. Also, on the bottom starboard cylinder, the spark plug was as clean as it went in brand new as if it has never fired. I attached a picture below. I'd also like to note that while warming it up for the compression check I checked the temperature with a laser thermometer. The port side cylinders were at normal temp of around 130 degrees but the starboard side cylinders were only getting up to around 110 degrees. This was after about 15 minutes at 1000 rpm.
 

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oldboat1

Fleet Admiral
Joined
Apr 3, 2002
Messages
9,612
Measure spark with an adjustable open-air tester (tells you if the ignition is strong or not). I would go to .030 point gap.
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,171
Get a different gauge and retest the compression. All those #s are terrible. Spark test is a waste of time until you confirm compression #s
 
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