Best way to evaluate motor with unknown history
 

In my new repo / winter project. At this point all I know is that it is a Gen V 1995 502 MPI that fires right up. Hour meter says 400 but it's not the original motor so who knows. Planning on doing a leak down and compression test next week. Any other suggestions to help me figure out where this motor is at and if I need to tear it down and rebuild or not? Thanks

Take the valve covers off and check the springs. If the boat will allow it, pop a rod cap off and check the bearings.

Cord,

Won't the leak down tell me if there is any problems with the springs. I'd have to pull the motor to check the bearing's, I wish there was another way.

Depending on ambition, you could possibly check for extreme valveguide wear without too much trouble. you could also boroscope inside the cylinders looking for big ridges at the top of the cylinders. Either of these may push you towards a rebuild even if it ran fine and had decent compression. Or you could run it till she pukes and in the mean time locate some good known low hour spare(s).

Have you got any run time on it yourself? does it use oil? have good oil p?

Almost forgot- run it in your driveway for a couple minutes, take an oil sample and send it to a lab for analysis (assuming the oil has some run time on it).

This can tell you a lot and it's pretty cheap- maybe $15-25, send a sample from the drive while you're at it.

No. A broken spring may still seal the valve. It just won't be able to rev and still control the valvetrain. It's also a good spot to check for moisture.


Lesson-I took my drive to the dealer the other day and asked them to check it for me. Well low and behold, the drive was OK. Unfortinately it's not good enough to put back togther. Now I have to come up with 2k to reassemble the drive. Sometimes you are better off not knowing as the check will proably turn up something that really wouldn't have mattered.

You may want to check the black box. You could check hours, and also check for any codes. this is assuming box has been with motor, and not a replacement block.

If it runs good and you did a leak down, change the oil and go out and play with it.

If leakdown is good and you are stuill worried, send an oil sample out, they will note any bronze or ferrous metal contamination. You can also remove and cut open the oil filter and see what's in the pleating. And a visual check of each and every valve spring is a must.

Oil samples are one of the best indicators of an engines internals, I would never buy an engine, drive or tranny without an oil sample.

How does an oil sample work? How much does it take? Where do you send or take it to? What does it cost? and what does it tell you?

Sound like a great idea I just don't have the slightest idea how to get it done:confused: