Outboard Compression

[Rudy AZ]

I've read this site for a while and asked questions before so I know there's some pretty informed people who contribute to it. Can anyone tell me the compression spec for a 7.5 hp Evinrude (83)? My manual doesn't have it listed and I don't know if 90 psi is OK or low. Yep, I know you're thinking why doesn't he go to Evinrude site to get this info. Well I did and many more as well. The company that bought OMC has Bombed the site. Thanks Rudy

 

[Justin - O'day Owners' Web]

Nice pun

Bombardier has indeed bombed OMC's old sites. I don't know the spec you need but I would suspect its ok - perhaps a little low but not too troubling. You've got compression of 6.4:1. This would be low in a new low emissions engine but could be right on for an older engine. Low compression ratios allow low grade gas without harmful detonation.What's going on to make you check compression?Justin - O'day Owners' Web

 

[Rudy AZ]

More on Outboard Pressures

Justin, Thanks for your help. I have a spare power head that's supposed to have 95 psi so 90 didn't seen that low to me. However with no referrence point, well... you got it. We keep the boat down in San Carlos, Mexico (Sea of Cortez) and had the Outboard Shop clean the carburetor due to stalling out upon approaching the ramp. It would not start again so I had to pull it into trailer with a dock line and crank it onto trailer. The mechanic said he was concerned with PSI and it had a cooling issue. Duh, I thought if water is coming out the back indicator tube then it's passing through the head (block) first, sometimes water seems hotter but I can still hold my hand under it. Years ago I fixed, overhauled cars and have done lots of mechanic stuff, but need to concern myself with safe sailing first, a scared wive doesn't help. Thanks Rudy