4.3 Harmonic Balancer

[Jmunk]

I helped a friend winterize his 4.3L and I happen to notice a faint but noticeable wobble of the harmonic balancer. I couldn’t tell if the outter portion of the balancer has slipped on the rubber or if the problem was with the crank snout itself as I didn’t pull the balancer.

The boat is a 2006 with the original engine that has never been out. I looked up the balancer part number while I was at the boat and had the serial number in front of me, the OEM part number is 888776T. Pretty pricey at around $400. I’m not sure how the crank snout could have gotten bent unless it was assembled with a out of spec crank?

I’m guessing the balancer is a GM part and not specific to Mercruiser? I found a GM balancer that has the same outter diameter but is listed for 5.0L and 5.7L. Anyone know a GM part number that crosses over to the above Mercruiser part number?

I need to pull the balancer, hopefully it’s not the crank snout.

 

[Scott Danforth]

Measure the diameter, it's a GM truck damper. Just get same diameter. It's a $50 part

 

[tank1949]

I helped a friend winterize his 4.3L and I happen to notice a faint but noticeable wobble of the harmonic balancer. I couldn’t tell if the outter portion of the balancer has slipped on the rubber or if the problem was with the crank snout itself as I didn’t pull the balancer.

The boat is a 2006 with the original engine that has never been out. I looked up the balancer part number while I was at the boat and had the serial number in front of me, the OEM part number is 888776T. Pretty pricey at around $400. I’m not sure how the crank snout could have gotten bent unless it was assembled with a out of spec crank?

I’m guessing the balancer is a GM part and not specific to Mercruiser? I found a GM balancer that has the same outter diameter but is listed for 5.0L and 5.7L. Anyone know a GM part number that crosses over to the above Mercruiser part number?

I need to pull the balancer, hopefully it’s not the crank snout.

Perhaps it was the pulley?

 

[stresspoint]

i just recently went through this fiasco and found some interesting info.

depending on motor year S/N the harmonic balancer / dampener could be unique to that year 4.3 motor .(crankshaft cast # , build location , boat or truck motor)
also the rotating assembly could be a balanced set from Mercruiser OEM on internal balanced Vortec 4.3 motor.
i recommend to do some internet research as i did to find the info you need relevant to your motor s/n,
as Scott Danforth posted above , they are mostly just a stock part that can be bought over the auto parts counter for 50 bucks.

however ,that said as my machinist said , sticking the wrong one on will cause vibrations and a very quickly worn out new balancer rubber dampener and possibly damage the crankshaft.
FWIW , i had my entire assembly balanced ( flywheel , crank , rods , and dampener) when i did my motor with the replacement dampener, i believe it needed some work to 0 everything out.

there was also talk of possibility's of later cranks with CPS pick up wheel having a longer snout requiring a unique balancer, but i don't know how much merit that has .

 

[Jmunk]

My knowledge, which could be wrong is that the harmonic balancer is neutral balanced and the flywheel has the weights for balancing.

Perhaps when getting a engine rebuilt at a machine shop they have the time to include the balancer into the rotating assembly. For mass production GM probably just balanced at the flywheel and tossed on a neutral balanced harmonic balancer for speed of production.

From what I saw in either 1986 or 1987 the 4.3 became externally balanced.

 

[stresspoint]

exert from the bible which i studied when i was learning about the 4.3 (thank you Scott Danforth ) ) >> However, you should also be aware that all of these engines are externally balanced with various combinations of flywheels/flexplates and dampers for balance, and that they are "trimmed" at the factory after the hot-run test by pounding balance weights into the holes that are already drilled in the damper. So, if you build them right and still have a shaker, the customer will have to add or subtract weight from the damper and/or flywheel/flexplate in order to get it right.

 

[Scott Danforth]

While GM claims to have "trimmed" the weights. it never really happened I believe that was PR

I also believe that for 2006, the 4.3, 5.0, and 5.7 all shared the same damper

 

[Lou C]

As much as I want a reman 4.3, one thing that concerns me is all the variations. Will the reman engine sellers get it right? Or am I better off with a local machine shop?
The easiest thing would be to replace what I have (pre Vortec, no balance shaft, roller cam, mechanical fuel pump) with the same thing then I can reuse my old flywheel and I have a spare fresh water used 12 bolt intake. However I don’t know if the rebuilders can find these old engines in good enough shape to rebuild. That’s why I started thinking of the V8 upgrade. Those you can still buy brand new! But more cost more has to be replaced.

 

[nola mike]

i just recently went through this fiasco and found some interesting info.

depending on motor year S/N the harmonic balancer / dampener could be unique to that year 4.3 motor .(crankshaft cast # , build location , boat or truck motor)

I don't think this is true, please provide a reference

also the rotating assembly could be a balanced set from Mercruiser OEM on internal balanced Vortec 4.3 motor.

Not sure what you mean here, but the 4.3s are internally balanced. Flywheels and balancers are not part of it. Merc or gm.

there was also talk of possibility's of later cranks with CPS pick up wheel having a longer snout requiring a unique balancer, but i don't know how much merit that has .

No merit. Non cps balancer will swap. I removed the reluctor on mine but not sure that's even necessary

 

[stresspoint]

I don't think this is true, please provide a reference

Not sure what you mean here, but the 4.3s are internally balanced. Flywheels and balancers are not part of it. Merc or gm.

No merit. Non cps balancer will swap. I removed the reluctor on mine but not sure that's even necessary

come on mate give me a break here , i read through soooooo many posts and references when i was building my motor i would not even know where i read that info.

i would love to share my findings and get confirmation from those that know these motors more than i do , fell free to PM me if you like .

 

[Scott Danforth]

No merit. Non cps balancer will swap. I removed the reluctor on mine but not sure that's even necessary

to keep the damper in the same location on carbed and EFI motors

 

[nola mike]

to keep the damper in the same location on carbed and EFI motors

when I was looking at it after the fact, it didn't seem that the reluctor interfered with the damper, but not sure. The damper came from an '89 and was installed in an '01 blazer block.

 

[QBhoy]

Hi. Had a friend recently with a hell of a knock off the engine, especially when stopping it or low rpm, when shifting out of gear. Was a 4.3 mpi. Turns out the balancer wheel securing bolt wasn’t home all the way (after some work done). It has a very small torque value…so what happened was that the area around where the bolt goes, was a little corroded and hadn’t been cleaned up before tightening down. It was basically torqued against a rough finish. So actually wasn’t all the way home to where it should have been. Couldn’t believe that was all it was, causing such a bloody horrible noise.

 

[Jmunk]

I’ll double check that bolt on the balancer.

I’ll try the GM balancer if the crank snout looks to be fine. Hard to believe the balancer would have slipped on the rubber with only a few hundred hours but maybe the age is more of a factor.

 

[Scott Danforth]

with only a few hundred hours but maybe the age is more of a factor.

Just about ever piece of rubber or plastic on a boat goes off a calendar and does not care if the hour meter ever tics over

Low hours on a boat means more things go wrong between uses and the boat sits.

If you are putting on 50hrs or less a year the boat isn't getting used enough

 

[Grub54891]

Seen to over the years that broke the crank just behind the lower timing gear. Those were chev 350's in cars/trucks. The pully was wobbly, but the darn things still ran. Scary when ya think about what could have happened. Don't think that's your issue but just a thing to check. Take the belts off and grab the pully and see if it wiggles around.

 

[nola mike]

Seen to over the years that broke the crank just behind the lower timing gear. Those were chev 350's in cars/trucks. The pully was wobbly, but the darn things still ran. Scary when ya think about what could have happened. Don't think that's your issue but just a thing to check. Take the belts off and grab the pully and see if it wiggles around.

Someone had a broken crank on here a few months ago, engine was still running, having a hard time timing iirc. V8 as well