force 50 sloppy piston?

Hello

I got this force 50 recently as a project motor. The motor is unusually clean. the cylinders have about 100 psi compression in them - not spectacular, but it should run. next I pulled the head and this is what I found (links below). the cylinders are cross hatched and the heads have little carbon on them. it seems like this motor was recently rebuilt due to an overheat, a problem with these engines. seems like it overheated because the thermostat is jammed WAY open. the motor seems like it could run for a little more though. one thing - does anyone know how loose the pistons can be in this type of motor? they seem a little to loose to me. what do you think? also, does anyone know who this motor is made by? It says US marine power all over it, but no indication of merc or chrysler.


https://drive.google.com/file/d/1kJTfq3BnVPC0CuKxyJUoDkgJqUeFV6kx/view?usp=sharing
https://drive.google.com/file/d/1JMtLGGIh6C8H7KFOyoV1Hrl-BUFYm8bE/view?usp=sharing
https://drive.google.com/file/d/1pCy2dwrtZqQd4ytqGAK4YcBdxD5QgIhP/view?usp=sharing
https://drive.google.com/file/d/12hSCIz36Sh5xMqYY9LZdmDeGYlU54qGb/view?usp=sharing

Even new pistons have quite a taper to them.---- Clearance is measured at the bottom of the skirt.------Pistons fit better once motor warms / heats up.----Co-efficient of aluminum is 0.000011" / degree F / inch.------US Marine was after Chrysler and before Mercury took over.

Bayliner Corp. They are part of a big conglomerate that owns Mercury, Sea Ray, Maxim
Mercruiser/Mercury.
The Boat Group makes Sea Ray, Bayliner and *******n pleasure boats; Boston Whaler offshore fishing boats; and Crestliner, Cypress Cay, Harris (formerly FloteBote), Lowe, Lund, Princecraft fishing, deck and pontoon boats.
And a few others.

Your motor looks like a 1989 50.
The "slop" is needed or it would get real hot and seize.
You can see the side of the pistons if you remove the port covers(2)
Replace the gaskets and use a sealer as an air leak will cause poor running/backfires and failure.

Compression at 100 is low, but since both are at 100 the low reading is probably
the way the test was done or the gauge is giving a low reading.
Some gauges give better results.

Put the head back on and do the test again.
Then run it.

Just sold a 2002 225 Mercury.
The new owner brings a NEW!! gauge from Harbor Freight.
Measures the first hole, 80# and the second again 80#
I said WRONG,
Went and got a good MAC tester.
150# all 6 cyl.