cylinder compression in tohatsu 40c

jwilkey84

Chief Petty Officer
Joined
Jun 26, 2005
Messages
524
I have a 73' evinrude 25hp and a tohatsu 40c, but the 25 has almost as much power/speed as my 40c. I have a manual from iboats, so I checked the compression with the engine warm, as instructed, and I got 78psi in the upper one and 92psi in the lower one. 78 is the recommended range for fixing. My question is, will boring it out and putting new pistons and stuff in give the motor more power/speed? Also is there a kit with everyting I would need? Approximately how much would it cost to do it myself, or someone else do it? Is it even worth rebuilding? I love the engine, it runs good, I just wonder is doing this will really give it more power and if it is worth it if the rest of the motor is good. The previous owner got the engine hot one day and I wonder if that is when the damage was done, or is this just something that happens with normal wear? Also I know 100 psi is normal, but how much difference should there be in the two different cylinders?
 

TOHATSU GURU

Admiral
Joined
Jul 22, 2004
Messages
6,164
Re: cylinder compression in tohatsu 40c

Yes<br />No<br />$300.00 for parts(at least), at least $300.00 for labor.<br />No<br />He burned it up.<br />There should not be more that 5 psi difference on that model.
 

jwilkey84

Chief Petty Officer
Joined
Jun 26, 2005
Messages
524
Re: cylinder compression in tohatsu 40c

Thanks for the quick reply. Maybe I can take the two engines and trade them at the local marina for one? Or I could just run the 40c till it dies.
 
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