Is it worth replacing the powerhead?

[displaced47]

My 1976 Johnson 70 hp had lousy compression (mid 50's all three) so I pulled the heads and the cylinders look smooth and ok. The local wrecker can get a used powerhead.

What would be included on the replacement? - Like does it have the pistons, crank, cylinders, etc?

Is it worth replacing it or should I do gaskets etc on the old one?

My old thread here http://forums.iboats.com/showthread.php?t=579418 has pictures of the head open.

thanks in advance - any advice would be appreciated.

 

[Lyle29464]

Re: Is it worth replacing the powerhead?

I would have to find out why 50# maybe carbon?

 

[Scott Danforth]

Re: Is it worth replacing the powerhead?

could just be carboned up rings.

you have to ask yourself if its worth it. I would ask my wallet. Most of the time it says find an inexpensive solution. you may also want to check craigslist. sometimes you can get a complete motor with a busted lower unit, or other simple problems for dirt cheap.

 

[displaced47]

Re: Is it worth replacing the powerhead?

I would have to find out why 50# maybe carbon?

Hi could you please explain what you mean by 50# ?
thanks

 

[displaced47]

Re: Is it worth replacing the powerhead?

could just be carboned up rings.

you have to ask yourself if its worth it. I would ask my wallet. Most of the time it says find an inexpensive solution. you may also want to check craigslist. sometimes you can get a complete motor with a busted lower unit, or other simple problems for dirt cheap.

I wish it were that simple for me but unfortunately (in this way only LOL) I live on an island in a relatively remote area and there isn't much for sale within 1000km from here.... i will keep looking though!

 

[Lyle29464]

Re: Is it worth replacing the powerhead?

Hi could you please explain what you mean by 50# ?
thanks

An even 50 lbs of compression with the wall looking good I would try to de-carbon the engine. look it over to find the problem.

 

[durban]

Re: Is it worth replacing the powerhead?

most likely the rings are stuck in the grooves & not expanding & that's where you lose compression

 

[displaced47]

Re: Is it worth replacing the powerhead?

Thanks for clarifying... looking at the cylinders two of them appear quite dark with carbon and the other piston head is white/grey and chalky... what would be involved in de-carboning the engine?

If I put it all back together do you think I would NEED a new gasket or would that be optional? Should the gasket have gasket goo on it?
thanks for your help!

 

[Lyle29464]

Re: Is it worth replacing the powerhead?

New gasket, no glue. Go to marine supply and tell them you want to remove carbon. search this site for reinstalling the head.

 

[phillnjack2]

Re: Is it worth replacing the powerhead?

being as compression was equal i would of got a different compression tester to make sure of the readings.

But to de-carbon it is very simple process and cheap.

you could end up with engine running good for very little money.

phill

 

[displaced47]

Re: Is it worth replacing the powerhead?

Thanks all - I will make some further inquiries (read other posts etc) and get back to you... Do you think there is any way to get by without the thermostat? I live in the tropics and there really is no time that the water should be shut off (salt water too).

Also the temp sensor looks rusty and probably dead is it necessary?

cheers

 

[Scott Danforth]

Re: Is it worth replacing the powerhead?

you need a thermostat to regulate water flow. without it, the water is moving too fast to transfer heat and you actually will overheat the motor.