1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

[SPolleyPT]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Mine did the same thing and all it needed was a fuel filter. The inline filter was clogged from sitting over the winter.
Good luck

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Update,

Checked the compression today, not good news. Checked each cylinder twice.
- cylinder 1 - 95
- cylinder 2 - 0!! ( guage needs about 20 to start to show pressure and it never did)
- cylinder 3 110

Show what next? obviously there is a big problem. Thinking of taking the heads off to look into the cylinder to see what it looks like? Any other advise or what I should be looking for?? Thanks

 

[Daviet]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Pull the head and see what your problem is.

 

[Monte1961]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Concurs^ with Daviet.

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Took head off, the cylinder in question has a hole in it. . . . not cool. I can see the ring in the hole and it is jagged and about to break. It has scratched the wall pretty bad. So . . . . bore all cylinders .030 over? or can I just do the middle one or what?

 

[Daviet]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

I know you can bore 1 cylinder .010 over with no problem, not sure about .030 over.

 

[larryg]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

do all of the cylinders,so that they are all equal.

 

[JWH0420]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

not familiar w machine work on outboards but generaly speaking u dont want to do just one cylinder will make things uneven

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Ya thats what im thinking. A buddy of mine know a place that will do them for me. So tomorrow I might strip down the engine and take it in there. ive never stripped an engine down before. but ill take pics and i have a book so all should b good

 

[Monte1961]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

If you do it right the first time, you shouldn't have to do it right the second time! If .010" is enough to clean up bad cylinder, then that's as far as I would go. The more cylinder-wall you have, the less chance your going to have other issues like overheating for one. Have all 3 cylinders bored the same, you don't want to run in to a balance problem. If there is any question on condition of original parts, replace them with new. Good luck on your new adventure and keep us updated. Please post pictures of your progress.

 

[clanton]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

There is no problems with just boring i cylinder. Oem pistons weigh the same. Oem only comes in .030 over. Find the service bulletins for cooling system , carbuator, and timing upgrades. prop to 6000 rpms after break in.

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

So I got the engine all tore down to the block. Waiting for the new pistons to get here so they can match it perfectly to the block when they bore it out. Only thing I really still need to find out before I reassemble is where and if any it needs gasket sealer or gel and what bolts need to be sealed.

- here is what was causing the problem, lol

 

[Ryan383]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Sorry I am new to this, how do I create a new thread?

 

[AlTn]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

look for a dark blue rectangular box at the beginning of the forums that says Start a New Thread

 

[emoney]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Y'up, David, I'd say that might cause a little problem, lol. So, what's the decision on boring, or did I miss that?

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Boing out all cylinders .030 over. Just got the pistons in the mail. Going to take them in with the block so they can bore it to the exact size of the pistons. Hopefully within the next few days. Then I can start putting it back together. I did end up ordering an all new water pump parts too so I need to get that put in too.

 

[dmoriarty51]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

latching on to this, as i have have a 95 70hp that has broken/melted the middle piston 2 times now.... currently trying to decide what action to take... im interested in these service bulletins as well

 

[davidkgt]

Re: 1990 johnson 70 hp, starts, idles. but no power. Only goes like 10 mph, HELP!

Update - Got everything done and put back together. Started it today, starting the suggested 10 hour break in. Seems to run a little rough though. I did do a link and sync and thought that I had it pretty good. Tried adjusting needle valve both ways and didnt really help. Not too sure what to try. I looked through the book too and that didnt help. I just dont want to do any damage if something isnt working right. Any suggestions?