Logo

Distributor gear worn in strange manner?

pursual

New member
First post, first time digging into a mercruiser or any marine engine.

I have a 1989 4.3 v6 175hp gm block, serial number missing. I was unable to find a block code that matched anything online. I pulled the intake manifold and noticed a strange wear pattern on my distributor gear.

I am going to replace it, but was looking for help as to what might have caused the wear? Also, is there a must-do ignition conversion for this engine, while I have the distributor apart?


Attached a photo of my gear.distributorGear.jpg

And this is probably what it looked like new? https://www.ebay.com/itm/Mercruiser-Distributor-Gear-43-818807-8M0115498-/362830137479
 
That would be the distributor's "driven" gear. And yes, it is showing signs of an unusual wear pattern, as in perhaps excessive resistance.

You will want to go in with a bore scope and look at the camshaft's "drive" gear before simply replacing this one.


.
 
You should inspect the timing chain.

if it is sloppy and needs replacement you may be facing a cam replacement also.

Was the distributor tightened down or was it lose?
 
Looks like excessive resistance(drag) in the distributor's shaft. Time to consider a Delco EST kit.
 
Last edited:
Or does the shaft have side movement in the dist housing? The movement will only be in one spot.

Great point.
If the distributor housing's lower bushing is heavily worn on the one side, the two gears will want to separate, possibly causing the unusual wear pattern.
As said, go in with a bore scope and look at the drive gear. It may be bad also.
 
Going to scope the cam tomorrow. The distributor shaft has a small amount of vertical play (seems normal, not sure if it was bottomed out when intake manifold was mounted), no apparent horizontal play. It is still tightly mounted, and spins normally as far as I can tell..not terribly easy, but not hard either.

This is an off topic question, but I just noticed this blown area on one of the head gaskets. Does this indicate anything in particular? It looks like it was designed to blow this way so I'm not sure if it's trying to tell me to check something. Would reusing this gasket for a quick compression test be unreliable? I am not sure I if I am going to have to bore the cylinders, so wanted to clean them and try a quick compression test before spending any $$.

gasket.jpg
 
...........
This is an off topic question, but I just noticed this blown area on one of the head gaskets. Does this indicate anything in particular? It looks like it was designed to blow this way so I'm not sure if it's trying to tell me to check something. Would reusing this gasket for a quick compression test be unreliable?
Yes...... it would be absolutely unreliable.

I am not sure I if I am going to have to bore the cylinders, so wanted to clean them and try a quick compression test before spending any $$.
By removing the cylinder head, you have now missed your opportunity to perform a cylinder leak-down test.

View attachment 25004
 
I had no choice on removing the heads, engine was seized. I have the cylinders cleaned and engine spinning (headless).

Though I know some of the fundamentals, I am really new to getting this deep into an engine of this size. I could really use some more detail in responses to questions I am asking.

Does the location of the blown area in the gasket mean anything, or ignore it and move on?
What's my best bet for judging the cylinder health at this point? Get new gaskets and do a compression test with them?
 
To move forward, Go to automotive parts store and buy cheap standard auto head gaskets for TESTING ONLY.

Reassemble and perform your testing (compression and if possible leak down test)

Also check flatness of head surface, V6 heads are notorious for warping due to over heating. My advice would be to send them out to shop for a proper exam and cleaning and flatness check not to mention valve condition.

Judging Cylinder health is not easy at your stage.
How thick is the carbon ridge at top of each cylinder? if fairly thick that would mean possibly high hours,

What do the cylinder walls look like when pistons are down in the holes?

Were the pistons stuck causing engine not to turn over? If yes, you may have piston ring issues and that will not be seen unless leak down test is performed or you see heavy scoring on cylinder walls.

So many decisions to be made and things to identify before final reassembly.................
 
Thanks Jack,
The pistons were stuck. This is an $800 dollar boat, and I don't want to put a ton of money into the engine. I may do a bore/rebuild down the line if I purchase a nicer hull.

The pistons and top of cylinders seem pretty clean. There is definitely wall pitting from the rust, but not any scoring. The block itself seems great for its age, might have been a remanufactured block. The rings are a mystery.

I plan on rebuilding the heads, just wanted to try to get an idea of how much compression loss I would have at the rings. I took your suggestion and am going to take the heads to a shop to see if they are warped. I might try a dirty compression test with the one unblown gasket, just to make me feel better.

Cam distributor drive gear looks fine...didn't realize it was so easy to see with the intake off. I guess I will be looking for an ignition replacement kit that has a new distributor as opposed to getting a new gear for the existing...don't want to risk a $60 new gear getting chewed again. Thanks all for the help!
 
I would look for a good used replacement distributor.
Plenty of cracked V6 mercruisers out there.
Might get one real cheap if you look around


Fellpro marine gasket kit!
Get the tag number. Should be riveted to block near above stater
To get correct year of engine if u suspect not original
 
I looked all over, there is no plate, and I couldn't even find engine block codes that matched what things online said to look for.
I fear my engine serial was on the flame arrestor, which I don't have. I do have the outdrive serial.
 
Can I buy a normal automotive harmonic balancer? Or do I need a marine one? I have a balance shaft 4.3.
 
Last edited:
I looked all over, there is no plate, and I couldn't even find engine block codes that matched what things online said to look for.
I fear my engine serial was on the flame arrestor, which I don't have. I do have the outdrive serial.


S/N stamped into block the S/N on flame arrest is just for convenience.
 
I definitely don't have a mercruiser plate, with SN. I def do not have a block code on the lip behind the distributor. I have the standard 14099090 on the passenger side of the block. It also says GM 4.3L, hard to tell if there is another character after the L. There are two characters under that that look like "56"? I have to look better in the daylight. I cannot find anything that looks like a standard GM engine code.

Balance shaft.
I have a 4barrel carb and intake, with elec choke.
Timing cover is plastic, vortec plastic valve covers. 8 bolt intake manifold.
Not serpentine belt.
I do have drain ports in the block so it is probably a marine block.

It's really hard to identify the engine, as the boat is 89, and a lot of the accessories probably are as well. Doesn't look like the elec choke was ever wired up! I am trying to replace the harmonic balancer but have no idea what year the engine is. I will look on the old balancer for any markings tomorrow. It is cracked on the rim.
 
Last edited:
How much $$$ are you looking at doing things the way you are approaching this?


Refurbished long blocks are under $2000.000

Your time is worth money so consider that also.



If you are looking at $1000.00 or more to do your "rebuild" then dont waste your time...........A refurb for $1000 more will give you many years of uninterrupted use vs a half ass rebuild will last a couple seasons then you will be starting all over again.......

Just my opinion....
 
Dropped the heads off today. That will get me up to $1035 total into the boat and another $50 into the trailer. $2000 would just get me a block, and most of the future costs are not block related.

I need at least 500$ of other things. Gasket set, Distributor or gear, balancer, thermostat housing, probably at least one hose, bellows, and maybe trim limit/cutoff switches (wires eaten by squirrels but possibly repairable). I have definitely learned a ton about mercruisers, so I am glad I opted to start with something cheap. I can probably recoup a decent amount, and I'll know a lot more what to look for on the next one.
 
Hope it's just the heads. I would quadruple your estimate of "other things". You probably need to redo the wiring and plumbing too. Have fun wrenching on it.
 
Update:

One head was cracked. Got a remanufactured pair for 150, have acquired new head bolts (fel pro, not as beefy as originals), waiting on a thread tap and an angle gauge to come from Amazon. Intake is blasted and painted. Replaced the carter fuel pump. Got the fel-pro marine gasket set, but am not impressed. The directions are weird, referencing blue beads (nothing is blue), and an "indentation" in the intake gasket "center hole" for a exhaust crossover restrictor (there is no center hole, or indentation in the gasket, probably will not use the little restrictor plates). Bought a 95 chevy s10 distributor gear, and while it looked similar, the shaft hole was too small. Returned.
 
First thing to understand,
The Mercruiser Thunderbolt ignition is a Marine only Mercury Marine ignition.

So there is no Auto compatible systems available.

Best to look for a dead V6 engine that you may aquire the distributor or just the gear
 
Back
Top