Ongoing Power Issues w/ '96 Johnson 90HP

Last summer (when I bought it), it ran great. Earlier this summer, it ran great in the driveway but wouldn't stay running in the water. I had the carbs rebuilt and general maintenance performed. I was also told I had considerable water in my gas. We took it out and couldn't get more than 4000 rpm's out of it. So, I removed all gas from my portable tanks, drained the hoses, and added a Racor separator with sight glass. I filled up the tanks with ethanol free gas. We took it out yesterday and it ran great, 'cept it wouldn't rev past 3000 rpm's. There was no water or trash in the filter, it started fine, idled a bit rough (how smoothly do these 2-strokes idle anyway), and had good power up to 3000 rpm's. In neutral, it would rev up to 6000 easily. Also, one side (bank of cyclinders) was a good bit warmer than the other, but all 4 plugs looked good.

Things that have been suggested for me to try:
1) drain carbs; could still be water and/or ethanol in the bowls not allowing enough gas under load.

2) a coil could be going bad. Get a replacement and rotate through the 4 until problem goes away.

3) check compression; I may have a cylinder losing compression.

I'm inclined to think #1 is the most likely, but I'd love to hear any other thoughts. I don't know the pitch of the prop, but it's the same one that was on it last year when it ran at 5200 rpm's. Thanks for any input!

David

Re: Ongoing Power Issues w/ '96 Johnson 90HP

A couple of thoughts, first NEVER EVER rev the engine that high on the hose, cold have serious results. Second I would pull the high speed jets and check for obstructions, on your carbs they are easy to get out and it will drain carbs at the same time.

Re: Ongoing Power Issues w/ '96 Johnson 90HP

Daviet said:

A couple of thoughts, first NEVER EVER rev the engine that high on the hose, cold have serious results. Second I would pull the high speed jets and check for obstructions, on your carbs they are easy to get out and it will drain carbs at the same time.

Click to expand...

Thanks for the suggestions on the carbs. I'll check them out this week. As for revving the engine... that was in the water. It wouldn't go past around 3000 in gear, so I put it in neutral and it easily went to 6000. I don't think I'd subject myself (or anybody else) to the sound of a 2-stroke revved to 6000 rpms without it being in the water!

Re: Ongoing Power Issues w/ '96 Johnson 90HP

i wouldnt rev it anywhere near 6000 rpms wether on muff or in the water...IN NUETRAL..


those kind of rpms need a load.....

I dont think reving past 3000 rpms is good in nuetral



good luck

bob

Re: Ongoing Power Issues w/ '96 Johnson 90HP

Guys,
I was on the water with a boat that wouldn't rev over 3000 rpms in gear. I put it in neutral to see if it would even rev like normal without a load... all part of the diagnostics and symptoms. This is not something I would normally do, it was only for a second or two, and it does not appear to have damaged anything.

Thanks for looking out for me (in terms of engine damage from revving to max rpms). Now, let's get back to helping me solve my motor's problems with running over 3000 rpm in gear... please!

bob johnson said:

i wouldnt rev it anywhere near 6000 rpms wether on muff or in the water...IN NUETRAL..


those kind of rpms need a load.....

I dont think reving past 3000 rpms is good in nuetral



good luck

bob

Click to expand...

Re: Ongoing Power Issues w/ '96 Johnson 90HP

DavidInWilmNC said:

Guys,
I was on the water with a boat that wouldn't rev over 3000 rpms in gear. I put it in neutral to see if it would even rev like normal without a load... all part of the diagnostics and symptoms. This is not something I would normally do, it was only for a second or two, and it does not appear to have damaged anything.

Thanks for looking out for me (in terms of engine damage from revving to max rpms). Now, let's get back to helping me solve my motor's problems with running over 3000 rpm in gear... please!

Click to expand...

have you checked the compression yet?????

have you gone and cleaned or replaced the high speed jets yet?

id try those first, then go to electrical second as those wont cost as much as a coil

good luck

bob

Re: Ongoing Power Issues w/ '96 Johnson 90HP

bob johnson said:

have you checked the compression yet?????

have you gone and cleaned or replaced the high speed jets yet?

id try those first, then go to electrical second as those wont cost as much as a coil

good luck

bob

Click to expand...

Finally, a weekend in town to get back to this. I just checked the compression, although I didn't warm the motor first as some recommend. Here are the results: 135 - 130 - 130 - 133. Based on those numbers, I'd think compression's not the issue.

I can't tell from my manual how involved checking the jets will be. Is it relatively easy (not too involved)? I had the carbs rebuilt in July. I may call the mechanic who worked on it and have check them again. He has a very good reputation for standing behind his work, so I doubt he'd charge much to do this (since I already paid him!)

Re: Ongoing Power Issues w/ '96 Johnson 90HP

Check the fuel pump, sounds like it's not getting fuel. Those motors get a small hole in the pump and it will not rev up.