MarkySparky
Seaman Apprentice
- Joined
- Jul 10, 2011
- Messages
- 37
working on a tight budget, bought boat with mercruiser 4.3 v6 with freeze damage. Replacement engine with very low mileage had bad bearings/damaged crank upon inspection. My question is can I safely put perfect crank from old engine into newer block, and use almost perfect pistons and rods that were in newer/low miles engine. If I could have a bottomless checkbook I'd have bought a brand new boat or at least brand new engine to put in this boat, but reality says "make do or do without"! Newer block cylinders and pistons look almost like brand new, and compression test before teardown of newer engine showed average of 170 psi on all cylinders,and it was very clean inside, so I feel its a waste to throw a lot of new parts and machine work at it. One possible issue I see is engine balance- are ALL engines balanced to their respective pistons/connecting rods at the factory, or just individual components to certain weight specifications? I know you pay extra for balancing an engine at a machine shop, and how that is done, but what about "factory-built" engines?
<EDIT> Just talked with one local machinist who is familiar with these engines and he said I should just put in new bearings and run it, as factory built and reman engines are not balanced so its very unlikely to be a problem. He could balance it for me but pistons are still connected to rods and he thinks he would likely break a piston trying to remove its pressed-in pin, so he won't unless I successfully removed pistons from rods. Also he said I should install a v-8 oil pump for higher volume, and put in a windage tray. Doing further online research, apparently some folks are having much success improving balance on their own engines by weight-matching piston/rod assemblies down to 2 grams or better and not worrying about the crank's balance, their engines reportedly running much smoother just making all their piston/rod assemblies the same weight at home. Yes, if I were replacing pistons etc., I would have the machine shop do a "proper" balance, but for now I'll just run with it!
<EDIT> Just talked with one local machinist who is familiar with these engines and he said I should just put in new bearings and run it, as factory built and reman engines are not balanced so its very unlikely to be a problem. He could balance it for me but pistons are still connected to rods and he thinks he would likely break a piston trying to remove its pressed-in pin, so he won't unless I successfully removed pistons from rods. Also he said I should install a v-8 oil pump for higher volume, and put in a windage tray. Doing further online research, apparently some folks are having much success improving balance on their own engines by weight-matching piston/rod assemblies down to 2 grams or better and not worrying about the crank's balance, their engines reportedly running much smoother just making all their piston/rod assemblies the same weight at home. Yes, if I were replacing pistons etc., I would have the machine shop do a "proper" balance, but for now I'll just run with it!
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