Is it the engine coupler that has gone bad?

[Spiderman210]

I have a Mercruiser inboard/outboard with Alpha One gen 2 drive. I took my boat out for the first time this season. Was pulling a tube for about 30 minutes when suddenly stopped moving. Engine running but no movement. I pulled the throttle back to neutral, put back into gear and no movement. This time put it barely into gear and was moving but not even at typical no-wake speed. Gave it more throttle and stopped moving again. Turned off the motor and lifted up covering to engine compartment and there was a smell, I believe it was possibly hot rubber smell. Got towed back to my lift. Put it on the lift, checked for a spun prop. Pulled prop off, prop insert and all parts seemed in great shape. The drive seemed to not have any issues. Pulled boat out of the water, took drive off, the gimbal bearing feels good and seems to turn smoothly. The engine coupler splines look good, I was thinking maybe the splines would be be totally stripped. Put the drive back on, put the throttle in forward (with the engine off) turning the prop counter clockwise by hand there is a growling vibration noise right at the transom heard while turning the prop. I had someone else turn the prop while I listened inside the engine compartment and noise seems to be at the engine coupler area.
When I saw that the engine coupler splines were not stripped out, as I thought it would be, I thought well it’s not the coupler. But can it be the coupler that has gone bad and the smell was something to do with the rubber in the coupler letting go? I’m new to inboard/outboard engines, I’ve had only outboards for past 30 years.

 

[dubs283]

Is there good clean full amount of lube in the drive?

 

[Spiderman210]

Yes, I drained it and put new gear lube in the day before this happened. And the reservoir was at full level. The drained gear lube looked really good.

 

[dubs283]

It's possible the hub in the coupler came loose from the rubber bushing. Rare, but does happen. If you can mark the coupler hub, rubber and the metal housing the rubber bushing is pressed into and test/spin the prop like you did before you can see if the lines no longer match up. Would indicate a spun hub in the coupler. Otherwise popping the top cap off the drive will allow you to see if there is any damage to the upper gearset

 

[Bt Doctur]

with motor off, shift into full fwd. prop should lock ccw. stand on a blade while someone watches the input shaft.
Prop turns,shaft turns=coupler issue.
Prop turns ,shaft does not= drive issue

 

[Spiderman210]

with motor off, shift into full fwd. prop should lock ccw. stand on a blade while someone watches the input shaft.
Prop turns,shaft turns=coupler issue.
Prop turns ,shaft does not= drive issue

With shifter in full forward, prop locks ccw and turning the prop ccw using two hands, the drive shaft going into the engine coupler turns the coupler. I can see the grease fitting on the coupler going around when the prop is turned ccw. It takes a good amount of effort to turn the prop ccw by hand.

 

[Spiderman210]

with motor off, shift into full fwd. prop should lock ccw. stand on a blade while someone watches the input shaft.
Prop turns,shaft turns=coupler issue.
Prop turns ,shaft does not= drive issue

If I remember correctly, before I took the boat out of the water, I started the engine trying to determine what was wrong and the vibration and noise was noticeable immediately with the drive in neutral. So I suppose if I started the engine with the drive removed, and if it is the coupler, the noise and all would be noticeable.

 

[Bondo]

When I saw that the engine coupler splines were not stripped out, as I thought it would be, I thought well it’s not the coupler. But can it be the coupler that has gone bad and the smell was something to do with the rubber in the coupler letting go? I’m new to inboard/outboard engines, I’ve had only outboards for past 30 years.

Ayuh,.... Welcome Aboard,...... If you smelled burnin' rubber, the steel piece with the splines, has debonded, broke free of the rubber donut it lives in,....
You need a new coupler,.....
'n check the alignment, as that's the usual cause of the failure,....

 

[achris]

With shifter in full forward, prop locks ccw and turning the prop ccw using two hands, the drive shaft going into the engine coupler turns the coupler. I can see the grease fitting on the coupler going around when the prop is turned ccw. It takes a good amount of effort to turn the prop ccw by hand.

You just described a spun coupler... 100% conclusive...

Pull the drive, pull the engine, replace the coupler, check the input yoke, (fully service the drive and unis while it's off), reinstall the engine and set up the alignment, push the drive on, go boating... You should be done by lunchtime...

Chris....

 

[Spiderman210]

Ayuh,.... Welcome Aboard,...... If you smelled burnin' rubber, the steel piece with the splines, has debonded, broke free of the rubber donut it lives in,....
You need a new coupler,.....
'n check the alignment, as that's the usual cause of the failure,....

Thank you for your help and taking the time to check out my issue. The alignment is good. Unfortunately for me the reason the coupler likely failed is because of the lack of it being greased. Like I said, I’ve had only outboard motors for over 30 years and that maintenance point is something I never thought of. Since it hasn’t been properly greased in last couple seasons, does that make it not surprising for it to of failed?

 

[Spiderman210]

You just described a spun coupler... 100% conclusive...

Pull the drive, pull the engine, replace the coupler, check the input yoke, (fully service the drive and unis while it's off), reinstall the engine and set up the alignment, push the drive on, go boating... You should be done by lunchtime...

Chris....

Thank you for all your help. One question concerning your answer, what do you mean by “check the input yoke”?

 

[achris]

Lack of grease will only damage the splines (either or both, the inside of the coupler and the yoke), not the rubber. Yours has failed, not because of lack of grease, and if the alignment is good, then something else....

Chris.

 

[achris]

Thank you for all your help. One question concerning your answer, what do you mean by “check the input yoke”?

Look at the splines, the unis and the general area around the front of the drive...

 

[Spiderman210]

Look at the splines, the unis and the general area around the front of the drive...

Installing a new Drive/Bell housing gasket set, is it recommended by Mercury and/or others to add gasket sealant to each side of the gasket or one side of the gasket or there is no need for any gasket sealant?
Also, the gasket set includes the O-ring for the water intake and the inner seal. But there are three additional O-rings, are they for replacing the ones on the shaft going into the engine or are they O-rings which fit different models and aren’t needed or are they to be installed elsewhere? I’m asking for an Alpha One Gen 2 drive.

 

[Bondo]

Installing a new Drive/Bell housing gasket set, is it recommended by Mercury and/or others to add gasket sealant to each side of the gasket or one side of the gasket or there is no need for any gasket sealant?
Also, the gasket set includes the O-ring for the water intake and the inner seal. But there are three additional O-rings, are they for replacing the ones on the shaft going into the engine or are they O-rings which fit different models and aren’t needed or are they to be installed elsewhere? I’m asking for an Alpha One Gen 2 drive.

Ayuh,..... I use tabs of grease to hold the gasket, 'n the o-rings in place, then mount the drive,.....
Most glue the o-rings, gasket dry,....
'n, Ya, the other o-rings are for the driveshaft to lock in the gimbel's inner race,....
Grease there for sure,..... slathered,....