4.3 Engine coupler issue?

[AMMO DAWG]

Finally got my 2004 Mercruiser 4.3 back in the boat after getting a front timing cover leak resolved and as I was aligning the engine I noticed if I aligned it and rotated the engine it would be way out of alignment. After messing with it for hours I put a 1" pipe in the coupler and cranked it over (see attached). Seems the coupler might be bent or crooked, have you ever seen an issue with a coupler like this? The engine was just rebuilt, had put it in and it leaked at the timing cover so I pulled it again, bought an OEM cover and new oil pan gasket and put it back in. I'm hoping I can just lift the engine and move it forward to get to the bellhousing and coupler versus pulling the engine. Any suggestions on checking the coupler after I pull it, thanks in advance.

 

[alldodge]

Never that bad. Need to pull the motor anyway to fix, but might be the coupler was not installed correctly. Either that or it sat a very long time not running and it was out of alignment then and coupler created a set

 

[AMMO DAWG]

So pulled the engine back and pulled the bell housing and the coupler appeared to be properly installed. Put my alignment tool in a vise, leveled it and ran a dial gauge across it while I spun it. I'm no machinist but it sure seems to be straight. Any other checks to recommend?

 

[Rick Stephens]

That doesn't seem sane.

I've heard of, never seen, a coupler where a rotten transom 'hung' the motor off the coupler and forced it out of center. Takes a long time with it parked and not run to do that I bet.

I'd call your coupler good with zero deflection... That said, where was the huge wobble induced? Bent pipe maybe? The pipe is too small to touch the gimbal bearing, so that isn't a factor.

 

[AMMO DAWG]

The outdrive hasn't been on the boat for the last two years while I had the engine out and I bought the coupler new and just installed it recently. The flywheel has corrosion, wonder if the coupler doesn't fit flat on the flywheel, mystery continues.

 

[AMMO DAWG]

All kinds of room to work back there, lol!

 

[Rick Stephens]

Since you have a magnet mount dial indicator, clamp a piece of angle iron across the transom plate motor mounts and stick the indicator there. Then spin the motor with the starter.

 

[Rick Stephens]

One other thing, it is possible that the issue is off center splines inside the coupler nose. You may need to stick the alignment bar in the coupler, or a short piece of 1" OD something, and indicate the that instead of the coupler nose.

 

[Scott06]

All kinds of room to work back there, lol!

The outdrive hasn't been on the boat for the last two years while I had the engine out and I bought the coupler new and just installed it recently. The flywheel has corrosion, wonder if the coupler doesn't fit flat on the flywheel, mystery continues.

Could be or might be a defective coupler was it oem or aftermarket? Do u still have the old coupler? If i recall you had freeze damage to the orig engine ?

 

[alldodge]

So pulled the engine back and pulled the bell housing and the coupler appeared to be properly installed. Put my alignment tool in a vise, leveled it and ran a dial gauge across it while I spun it. I'm no machinist but it sure seems to be straight. Any other checks to recommend?

I'm no machinist either but that way you have it setup is not telling me anything. Sticking a pipe in the coupler and then rotating it says nothing about out of round. If it was still connected to the motor and the pipe was not in a vise I would say yes.

Move the dial indicator on the rear face of the couple as far out as you can and see what happens

 

[AMMO DAWG]

Thanks, it is the same engine, took it back to the machine shop that built it and they did a pressure test and leak down test, turns out it had a bad head gasket, no cracked block or head glad to report. I have run it quite on bit on the ground and oil is good. I see your point on the quick test I did, when I can get back on it I will take Ricks advice and get the dial gauge on it while it is spinning. I also got a piece of 1-inch steel rod (12-inch long) headed my way to take that hollow aluminum pipe out of the equation. Still considering pulling the flywheel to have a look. Have any of you ever had a mercruiser flywheel surfaced to insure it is flat and true? As always I really appreciate what you guys do on this forum, the extra advice keeps me from making the old tub the start of a new reef!

 

[alldodge]

Never seen a flywheel get warped

 

[tank1949]

Finally got my 2004 Mercruiser 4.3 back in the boat after getting a front timing cover leak resolved and as I was aligning the engine I noticed if I aligned it and rotated the engine it would be way out of alignment. After messing with it for hours I put a 1" pipe in the coupler and cranked it over (see attached). Seems the coupler might be bent or crooked, have you ever seen an issue with a coupler like this? The engine was just rebuilt, had put it in and it leaked at the timing cover so I pulled it again, bought an OEM cover and new oil pan gasket and put it back in. I'm hoping I can just lift the engine and move it forward to get to the bellhousing and coupler versus pulling the engine. Any suggestions on checking the coupler after I pull it, thanks in advance.

I had a similar problem due to the fact that my engine compartment was restricted for my partner to make sure all rear engine mounts and PARTS stayed in alignment. This problem happened installing Chevy V8s. We kept dislodging leather washers and didn't see that they had been dislodged. Pray your transom is not rotten, which would cause flexing. Since you had motor out, make damn sure parts went back in and you didn't have any extra stuff in the bilge.

 

[AMMO DAWG]

Thanks Tank! Pretty sure the transom is good, and not sure if it's an approved method but I put a few drops of two part epoxy to hold the leather washer in place cause you're right, no space at all.

While trying to dodge rain I did some more low tech testing, I put the new coupler on with a 1" solid steel bar which I verified is straight and spun the engine, then put the old coupler on and did the same. (see videos) I think the problem is the coupler, thoughts? The old coupler teeth are pretty worn, other wise I would just put it back on. I know I should order an OEM, but I have sticker shock, anybody had any luck with aftermarket couplers?

 

[Rick Stephens]

New coupler is scheitz

 

[tank1949]

Thanks Tank! Pretty sure the transom is good, and not sure if it's an approved method but I put a few drops of two part epoxy to hold the leather washer in place cause you're right, no space at all.

While trying to dodge rain I did some more low tech testing, I put the new coupler on with a 1" solid steel bar which I verified is straight and spun the engine, then put the old coupler on and did the same. (see videos) I think the problem is the coupler, thoughts? The old coupler teeth are pretty worn, other wise I would just put it back on. I know I should order an OEM, but I have sticker shock, anybody had any luck with aftermarket couplers?

something made the couple go bad or warp. General wear? Maybe.... Over decades, I have owned several MCs and only replaced one coupler. While motor is out, drill a few holes into transom to check for ROT. You can easily fill holes with 5200 and sleep well later on. Good luck.

 

[Rick Stephens]

something made the couple go bad or warp. General wear? Maybe.... Over decades, I have owned several MCs and only replaced one coupler. While motor is out, drill a few holes into transom to check for ROT. You can easily fill holes with 5200 and sleep well later on. Good luck.

As noted, the crooked coupler, while bought last year, is never used.

 

[dubs283]

Um....did you properly install the rear engine mounting hardware correctly?

Takes a spring and fiber washer with appropriate mounts on the flywheel cover

 

[Rick Stephens]

Um....did you properly install the rear engine mounting hardware correctly?

Takes a spring and fiber washer with appropriate mounts on the flywheel cover

The point is there is HUGE wobble in a 1" shaft installed in that new unused coupler. The motor is not even setting on the mounts, just the stub sticking out of the new coupler. When spun you can see a 1/4" of runout just on that 6" stub of round stock.

 

[AMMO DAWG]

After scouring the old inter-web for a new coupler come to find out OEM couplers are very pricey and the next best (in my opinion) the Sierra are sold out anywhere that has them for a decent price. There's lots of Chinese aftermarket couplers out there, but I'm not going to do that again. So, I cleaned up my old coupler and took a good look at it again. One problem I had was the alignment tool wouldn't go in the spline area, it had a hard stop. After investigating further it looks like an alignment tool or maybe the outdrive shaft had been forced in dinging up the outer edges stopping the tool. A 1" rod would go in, but the tool is a bit larger and has a tighter tolerance. I cleaned up the mushroomed edges lightly with a file and now the alignment tool and outdrive shaft slide in just fine. I took some pictures of the splines, I'm leaning toward looks good to me, like some opinions based on the pictures below. Need a tourniquet on the money hemorrhaging if possible, lol! Thanks again.