1999 Johnson 70hp 3 cylinder, one cylinder lost most of its compression. I have the head off and will get a head gasket. Should that fix it? I fear it got hot when my nephew pulled skiiers this fall.
If the head gasket is the problem then there should be an obvious sport on the steel ring of the gasket where it is burned through to allow the compression to escape.<br />Like DJ asked. What does the cylinder wall look like?
I was thinking about putting on a new head gasket then test it again, if this doesnt fix it can I pull the head back off and save the gasket? <br />I could then put a new head on? or try and fix the current one, not sure how to tell if the head is bad?
Ive toaste mine a couple times....over-revving and pulling a heavy load into a wind that wouldnt allow full throttle were my hard lessons.Premium fuel ,espeacilly in the wintertime blend will cook your insides.<br /> I always had signs of ring damage and lost #2 both times.<br /> Make sure you are propped right and have a tach.Teach your kid about the redline and how you dont go any faster when you hit the upper end of the powercurve.<br /> A leaned carb or bad timing setting will cause the trouble if the cooling system isnt the initial problem.<br /> Also run the engine tuner to rid the carbon.<br /> Tim M
Since you have the head off you have to locate what went bad. Stabbing around changing this and that is a time and money waster. Every time you pull the head you'll need a new gasket.<br />If the gasket,the head and the piston appear OK then it could be the rings (stuck or broken) or old fashioned cylinder wear. <br /><br /><br />Charlie
Theres a reason for the damage Tim. And theres no such thing as going over the "red line". The rev limiter is at 6700 and it'll stop there on its own. If youve damaged the middle cylinder twice, you need to correct the cause -- not just fix the effect. <br /><br />The middle cylinder runs the hottest on that design. Ive seen more of those cook the middle cylinder running around at 3800 rpm than at full throttle. There are things to do to cool down #2.
