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1972 Johnson 65hp 65ESL72S

B

brent

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" My motor is a little hard to

" My motor is a little hard to start but when I get it started it idles
great. put it in full throttle and it starts to take off great for a
few seconds then chokes down like its at half throttle but the lever
is still all the way up.

I took it to the boat shop and the guy told me that compression was an
issue ( 1st cylinder is 115, 2nd is 85 and 3rd is 100. He also told
me that he couldnt get any spark and that my power pack had probably
went out.

I got a new power pack and took it to the lake and BAM . she took off
like a champ for about 5 minutes then back to the same old thing of
choking down.

I also got a new head gasket thinking that the head gasket may be
blown making it seem that I had a bad cylinder but havent replaced it
yet. (planning on doing that this weekend.

Ordered a book that shows parts, repair, and service for the motor but
it hasnt came in yet. I think I can handle the head gasket though.

New fuel tank, lines, and the carbs have been cleaned about 2 weeks
ago before I picked it up from my dad.

I think this is about it. Any help would be greatly appreciated.

I look forward to hearing from you.

Thanks alot, "
 
" You've got 30 pounds dif

" You've got 30 pounds difference in compression between the lowest cylinder and the highest cylinder. That spells out either a blown head gasket or a powerhead that is in need of an overhaul.

If a gasket was blown that bad, the cylinder would also be getting water in it from the adjacent water passages. In all probability, when you remove the cylinder head, you'll find out which of the two scenarios you're facing.

The usual cause of having a piston fail with the resulting lowering of the compression is a fouled carburetor which causes the engine to run lean.

Joe "
 
"Joe -

If it is a piston or

"Joe -

If it is a piston or carb, why would it run fine for a while before
choking back down?? Heat?? That is why I thought it may e the gasket
working while engine is cold and once the engine warms the gasket it
starts to fail? Not sure on this scerino but possible?

Once I change the gasket I am going to do another compression test to
see if that fixes the compression issue. If it does, where should I
turn? To the Carbs again?

I do appriciate your quick response to the last message.

--
Best regards,
Brent mailto:[email protected]"
 
" ALL -

Well I just finishe

" ALL -

Well I just finished replacing the head gasket and noticed something that may be of a problem. At the bottom left hand corner of the head cover there is a round sensor of some sort that comes out and had 2 wires that screw into a panel on the oppisite side of the motor. One of the wires was pulled out of the piece of the "sensor" (which is about the size of a nickle and about a half inch thick).

Is this piece detrimental to the working of the engine. AND is it a part that I can get. I pushed the wire back into the hole and made sure its tight but dont know if that will fix that specific piece. It has started raining on me so I can't go and see if the engine will run properly.

And I have to wait until Monday to see if my compression issue is fixed since I replaced the head gasket.

BTW - all 3 cylinders looked great, with no scoring or grooves.

Thanks all,

Brent "
 
That is a temperature sensor

That is a temperature sensor for the choke and it does not affect engine operation once motor is warmed up. You can bypass the affect of this sensor bu pushing the choke all the way in manually.
 
" Sparky,

I appreciate the

" Sparky,

I appreciate the info. I took the boat out this afternoon and I couldnt get it to crank over very good. I took my starter off and took it apart. The brushes were dirty and where the brushes touch was corrioded. I cleaned all parts of the starter and creased the shaft. Is there anything else to the starter? I havent put it back in cause its dark. I will post tomorrow when I get it back in to give results. "
 
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