1958 Fastwin cylinder psi mismatch - concerns

mologus

Cadet
Joined
Aug 27, 2003
Messages
23
My 1958 Evinrude Fastwin is measuring 60 psi on one cylinder and 100 psi on the other. What is goin on here?<br /><br />Also both coils(?)are cracked badly. But still get good spark. So far the engine will not run even after rebuilding the carb. Spits and backfires on me. Is this due to psi mismatch on cylinders?<br /><br />Got motor month ago.<br /><br />(how do I know plug wires are not switched?)
 

emckelvy

Commander
Joined
Jan 16, 2004
Messages
2,506
Re: 1958 Fastwin cylinder psi mismatch - concerns

It might run if you had good spark.... you'll never get that motor started with cracked coils.<br /><br />40 psi diff is not so good either but the motor should at least run, albeit poorly. You may have a bad head gasket; or, perhaps if you get it running you can run some Seafoam or other decarbonizing spray thru the motor in hopes of freeing up the rings. If your motor has intake port covers, they can be easily removed to check the condition of the rings. Or, pull the head and check the pistons/bores. <br /><br />Check the head gasket for leakage and if you see an uneven clamping pattern on the gasket, likely the head is warped and needs to be milled flat. Or you could do it yourself with wet/dry sandpaper on a thick piece of glass.<br /><br />But those coils aren't going to cut it. Any old JohnRude with cracked or oozing coils is going to have spark problems. Replace the coils and it should run.<br /><br />HTH.........ed
 

rolmops

Vice Admiral
Joined
Feb 24, 2002
Messages
5,299
Re: 1958 Fastwin cylinder psi mismatch - concerns

Before you dump any mony into that engine,make sure that the compression difference is only caused by sticky rings or carbon buildup.Take the plugs out pour a good amount of penetrating oil or seafoam in the cylinders and let it sit for a day or 2.Now try and get the engine to run or at least turn it over often enough to make sure all the penetrating oil is gone and do another compression test.If that improves the compression to the point where the 2 cylinders are within 10% difference from each other you should invest in coils, points,plugs and condensers and you can probably get her to run as good as she did in 1958.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1958 Fastwin cylinder psi mismatch - concerns

just pull the head and have a look<br /> its quick and easy. if the cylinders are chewed then go find a motor.<br /><br /> good luck and keep posting
 
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