1995 Mariner 60hp cylinder compression

[Coxn]

I've got a couple of 94-95 2 stroke Mariner 60hp engines. Both have compression issues, but I'm hoping to rebuild a good one out of the two by honing one block and using the best of the remaining pistons and rings. I've got 105psi across all three cylinders cold, but she runs rough and compression drops to 90psi when warm. I thought PSI went up when everything had warmed and expanded?

I could spend money on getting her rebored and fitting a new piston kit, but I'm concerned about a cracked block as well. Any advice on checking the jacket for leaks?

 

[frustratedboater]

Given the year, I would bet that your rings could be getting worn and or gummed up with carbon (or need replaced, but would require that re-build with a good criss-cross honing).
You could spray a [little] seafoam into the cylinders to throughly work into the cylinders and allow to pre-soak over-night or all day. Shoot them again with a little more and move the flywheel back and forth a few inches to work into the rings and let sit. This should free up the rings on the pistons to rejuvenate them.
At start up, you'll see a little extra smoke due to the oil burning off, but will clear. You'll also see thin black oil dripping from the drain hole in the side of the lower unit. It's just draining out. I like to add some boat soap in my barrel to 'scrub' the insides.. It will also flush out when running. That's what I'd try to see any compression increase if any.
Just my two cents worth towards a remedy.. Good luck!

 

[Faztbullet]

Honing a worn block and installing used worn parts get you a worn motor. Bite the bullet and bore .020 with new pistons and gaskets If the new style looper block( 59ci) it is rare to have a water leak only if cracked from severe heat or physical damage. These blocks suffer more from sleeve slippage due to overheating /bogging. Everyone I rebuild I pin the sleeves in place

 

[Coxn]

Honing a worn block and installing used worn parts get you a worn motor. Bite the bullet and bore .020 with new pistons and gaskets If the new style looper block( 59ci) it is rare to have a water leak only if cracked from severe heat or physical damage. These blocks suffer more from sleeve slippage due to overheating /bogging. Everyone I rebuild I pin the sleeves in place

Thanks for the input. Yeah, looks like my attempt to rebuild from the best parts I have is not going to pan out. The hone looks good, but 90psi hot is pretty low for this engine I think. I was told by someone else they began with 140-145? Can anyone else confirm that?

 

[frustratedboater]

Thanks for the input. Yeah, looks like my attempt to rebuild from the best parts I have is not going to pan out. The hone looks good, but 90psi hot is pretty low for this engine I think. I was told by someone else they began with 140-145? Can anyone else confirm that?

And.. boring the block is the other option! Didn't know how deep you wanted to go.