Back story, I recently bought a boat with a 2003 90 HP 2-Stroke Mercury. I checked compression when buying, it was all within reason (If I remember 110, 120, 110. One afternoon I took the boat out for a stroll. 5 minutes in, it shut-off on me, I popped the cowl, out of oil. Before anyone says anything, I know I should've checked it before going out. But was racing daylight and didn't think of it.
The motor itself was still cool, only ran for roughly 5 minutes. I got pulled back to the ramp and loaded on the trailer. After getting back home, I put more oil in and ran on muffs, it ran perfect. I got busy and let the boat sit for 2 weeks. Just recently I had an open afternoon and decided to take the boat back out. At the ramp it wouldn't crank and I hauled it back home. I checked the fuel, and the engine was getting fuel perfectly.
My next step was pulling the plugs to ensure spark, all 3 plugs are getting spark. However, a good amount of oil buildup was easily seen on the plugs. I then checked the compression, on full throttle. From the top, the compression is as follows, 30, 120, 80, also this is while the motor is cold as it is currently not running. I also checked that all cylinder was cycling, and they all are. I bought a camera to see inside the cylinder before popping the head, it arrives tomorrow. But I wanted to come on here and get other people's opinions. The motor does still have the built-on external tank, and oil is not mixed in the gas.
I believe it could be the following:
Reed Values
Blown Head Gasket
Piston Rings
Potentially cracked piston or cylinder, but very much hoping not.
I am not the most mechanically inclined individual, and hoping to get any feedback on which to rule out first and what's more likely. I have to fix this myself, as my wife would kill me if I paid mechanic prices.
The motor itself was still cool, only ran for roughly 5 minutes. I got pulled back to the ramp and loaded on the trailer. After getting back home, I put more oil in and ran on muffs, it ran perfect. I got busy and let the boat sit for 2 weeks. Just recently I had an open afternoon and decided to take the boat back out. At the ramp it wouldn't crank and I hauled it back home. I checked the fuel, and the engine was getting fuel perfectly.
My next step was pulling the plugs to ensure spark, all 3 plugs are getting spark. However, a good amount of oil buildup was easily seen on the plugs. I then checked the compression, on full throttle. From the top, the compression is as follows, 30, 120, 80, also this is while the motor is cold as it is currently not running. I also checked that all cylinder was cycling, and they all are. I bought a camera to see inside the cylinder before popping the head, it arrives tomorrow. But I wanted to come on here and get other people's opinions. The motor does still have the built-on external tank, and oil is not mixed in the gas.
I believe it could be the following:
Reed Values
Blown Head Gasket
Piston Rings
Potentially cracked piston or cylinder, but very much hoping not.
I am not the most mechanically inclined individual, and hoping to get any feedback on which to rule out first and what's more likely. I have to fix this myself, as my wife would kill me if I paid mechanic prices.