Silly Seville
Senior Chief Petty Officer
- Joined
- Dec 5, 2009
- Messages
- 798
Hi Guys, this is long and probably complicated. I appreciate your patience.
I'm in a real pickle here, and I hope the solution is really simple, and I'm just making it more difficult than it needs to be.
I bought a 1988 boat with a Mercruiser 4.3LX 205hp V6. Block and heads were freeze damaged beyond salvage. I knew this when I bought the boat (very very cheap) My intention was to drop a more modern 2000 model Chevy Vortec V6 from a truck in it's place, since I have done that successfully twice before with 350 V8's. The only fundamental difference between a 1988 and 2000 model 4.3 V6 is the '88 was not a balance shaft engine, and of course did not have the Vortec heads.
I stripped every last marine specific part off the junk engine before tossing it, and kept nothing from the donor truck engine since none of the accessories designed for the truck are compatible in the boat. The truck engine had a flexplate, (automatic tranny) so that was tossed since I clearly couldn't use it. I did keep the truck engine harmonic damper believing that it had to stay with the rotating assembly, and thought I would be able to use the flywheel from the original junk engine.
Well, here is my dilemma. The truck engine used a serpentine drive belt with the wide single crankshaft pulley and a small, lightweight damper (6.25")
In contrast, the original boat engine uses a heavier 6.75" diameter damper, and two single groove V-belt pulleys stacked on each other. The double stack V-belt pulleys will not mate with the smaller diameter damper. I have to use those pulleys! So the million dollar question is...can I use the stock damper that came on the boat engine, or will that throw off the reciprocating balance of the much newer Vortec engine? The same question also applies to the flywheel. Can I use the original 1988 boat engine's flywheel on this 2000 model V6, or will I have to replace it with a flywheel specific to this engine?
Before anyone answers, I will tell you I already asked the machinist who prepped the block for me the same questions. He said that I must continue to use the smaller lighter harmonic damper that came with the truck engine, but that I could throw any old SBC flywheel on there I wanted, (assuming 1 piece rear main seal version) and the reciprocating assembly wouldn't know the difference.
I found that hard to believe since the flywheels are weighted for specific engines from the factory. If he's wrong, I'm going to have to pay big money to have a shop balance the engine, and I really don't think that's necessary with the original rotating assembly still in place. I don't mind buying a new flywheel and harmonic damper if necessary to keep this engine from shaking itself apart, but I also don't want to toss the original equipment if it will function just fine with this newer engine.
Am I making this more complicated than it really is, or does the size and weight of the harmonic damper really have a profound affect on the internal balance of the engine, in conjunction with the weighted configuration of the flywheel? BTW, I tried finding a harmonic damper specific to the 2000 model engine in a version that would accept the double V-belt pulleys, and as far as I can tell, such a damper doesn't exist.
Thanks to everyone in advance who has an opinion or advice in this matter, and keep in mind, I'm typing this at 4:30 am. Maybe I'm too tired to think straight!
I'm in a real pickle here, and I hope the solution is really simple, and I'm just making it more difficult than it needs to be.
I bought a 1988 boat with a Mercruiser 4.3LX 205hp V6. Block and heads were freeze damaged beyond salvage. I knew this when I bought the boat (very very cheap) My intention was to drop a more modern 2000 model Chevy Vortec V6 from a truck in it's place, since I have done that successfully twice before with 350 V8's. The only fundamental difference between a 1988 and 2000 model 4.3 V6 is the '88 was not a balance shaft engine, and of course did not have the Vortec heads.
I stripped every last marine specific part off the junk engine before tossing it, and kept nothing from the donor truck engine since none of the accessories designed for the truck are compatible in the boat. The truck engine had a flexplate, (automatic tranny) so that was tossed since I clearly couldn't use it. I did keep the truck engine harmonic damper believing that it had to stay with the rotating assembly, and thought I would be able to use the flywheel from the original junk engine.
Well, here is my dilemma. The truck engine used a serpentine drive belt with the wide single crankshaft pulley and a small, lightweight damper (6.25")
In contrast, the original boat engine uses a heavier 6.75" diameter damper, and two single groove V-belt pulleys stacked on each other. The double stack V-belt pulleys will not mate with the smaller diameter damper. I have to use those pulleys! So the million dollar question is...can I use the stock damper that came on the boat engine, or will that throw off the reciprocating balance of the much newer Vortec engine? The same question also applies to the flywheel. Can I use the original 1988 boat engine's flywheel on this 2000 model V6, or will I have to replace it with a flywheel specific to this engine?
Before anyone answers, I will tell you I already asked the machinist who prepped the block for me the same questions. He said that I must continue to use the smaller lighter harmonic damper that came with the truck engine, but that I could throw any old SBC flywheel on there I wanted, (assuming 1 piece rear main seal version) and the reciprocating assembly wouldn't know the difference.
I found that hard to believe since the flywheels are weighted for specific engines from the factory. If he's wrong, I'm going to have to pay big money to have a shop balance the engine, and I really don't think that's necessary with the original rotating assembly still in place. I don't mind buying a new flywheel and harmonic damper if necessary to keep this engine from shaking itself apart, but I also don't want to toss the original equipment if it will function just fine with this newer engine.
Am I making this more complicated than it really is, or does the size and weight of the harmonic damper really have a profound affect on the internal balance of the engine, in conjunction with the weighted configuration of the flywheel? BTW, I tried finding a harmonic damper specific to the 2000 model engine in a version that would accept the double V-belt pulleys, and as far as I can tell, such a damper doesn't exist.
Thanks to everyone in advance who has an opinion or advice in this matter, and keep in mind, I'm typing this at 4:30 am. Maybe I'm too tired to think straight!
