Compression on older 150hp evinrude
 

Hi All Anyone know what the compression should be on a older 1986 150hp evinrude ..I know on most outboards the comp. should be over 100 psi and even on all cycls.. But I am getting conflicting info on theses motors ..Some posts on google state that the big old motors were only rated at 80-90psi and some other post state 110-120..they state some as loopers and some as crossflows I think,,, which I have no idea what either are..THANKS

If it's any help, my 1991 200 HP Johnson's compression is in the low 90's.. right where it should be.

86 150 EVINRUDE will be a cross-flow engine and have a bubble back exhaust on it most likely. The looper engines will have a one piece block whereas the cross-flow engines will have plates that bolt onto the sides of the cylinders and the exhaust will also have a plate bolted on it between the 2 heads. The main thing to look for is that all the cylinders are the same or within 5-10% of each other. Normal compression on that engine should be in the 90-100 pound range on a fresh tight engine, but years of use and carbon build-up can and most likely will change those numbers.

Had an "84 150 horse on the V before repowering with the current motor.
At the time of swapping out the engines it had 89/90psi on all cylinders, same as it was 3 years prior to mounting it on the boat.
Like ferm said, most important thing would be near even compression between all the cylinders.