Johnson 250 V8 Outboard Low Compression on top 2 cylinders

[skidog519]

I have a 1993 Johnson Ocean Runner 250 V8. Outboard with 519 hours on it. A leak was found in the intake gasket so a compression check was performed on the cylinders. All of the cylinders were around 120 lbs except the top two cylinders one was 55 lbs and one was 85 lbs. The tech pulled the heads off and checked the inside of the cylinder wall on the questionable cylinders. I was with him when this was done and there was a little scoring on the wall of both cylinders. I was told it needed to be tore down and the heads machined .010 over and new pistons put in the top two cylinders. There is no other damage. I was told depending on what they found when they tore it down it would cost between $2,000 and $3,000. I about fell off my boat when I was told the price. They claim it would take around 24 hours of labor to tear it down, fix it and put it back together. Can anyone tell me does this sound right? It just seems outrageous to me so anybody who has a thought I would like to hear your opinion.

 

[kenmyfam]

Re: Johnson 250 V8 Outboard Low Compression on top 2 cylinders

Photo of the scoring would be a great help.
Tear down on a V8 motor is never cheap and then you have the machining, new gasketry and rebuild to consider. I would be more interested as to why the top 2 cylinders have scoring and not the others. You have to root cause the issue and fix it as well or you will be posting the same question shortly after you spend all that money. Could be running lean up there and not getting the lubrication it needs.
You pays your money and you takes your choice, put the repair money toward a replacement motor or fix this one up.
Do you need all of the 250hp you have ???

 

[skidog519]

Re: Johnson 250 V8 Outboard Low Compression on top 2 cylinders

Could of it been caused by the intake gasket leaking? The scoring is not that bad very minimal but I do not have a picture. The motor is on a 21' Boston Whaler Center Console. It is a lot of motor and not very fuel effieicent

 

[jonesg]

Re: Johnson 250 V8 Outboard Low Compression on top 2 cylinders

Could of it been caused by the intake gasket leaking? The scoring is not that bad very minimal but I do not have a picture. The motor is on a 21' Boston Whaler Center Console. It is a lot of motor and not very fuel effieicent

Yes, an air leak is like over-advanced timing.

I'd go for it, you'd be hard pressed to replace it at that price.
Well I think I'd have a go at doing the breakdown and rebuild, have a machine shop do the cyl work. That would save the lions share of the cost.

 

[skidog519]

Re: Johnson 250 V8 Outboard Low Compression on top 2 cylinders

You said you would have a go at doing the tear down or did you mean I should have a go at it. That would end up costing me way more by tearing things up or not getting i tput back correctly. Yes I agree it is way cheaper than a new one

 

[jonesg]

Re: Johnson 250 V8 Outboard Low Compression on top 2 cylinders

"Cannot lives on Will-not street".

I don't know that I could do it, but I'd sure be trying rather than predicting failure.

You're gonna need the shop manual, a hoist to pull the block and a workbench. A marine machine shop will machine the holes and fit the new pistons to the bore, around $200-300 job.
Have all the holes honed and re-ring the other pistons, like a new engine.
Engine hoists on craigslist $125 all day long.

Get the shop manual and have a good read, there isn't a lot to a 2 stroke engine.
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