Merc 120HP engine coupler / or spun prop?

[Fordiesel69]

On my searay in the signature, I had it out in our bay today and it was choppy. Moreso than other times I had it out.

I noticed at times, the engine would rev up slightly and I would feel a slight vibration. It kinda felt like torque converter shudder. My question is how can I find out if it is the engine coupler, or prop spinning. I am going to mark the prop now and see what happens.

 

[Fordiesel69]

Re: Merc 120HP engine coupler / or spun prop?

Anyone?

 

[ErieRon]

Re: Merc 120HP engine coupler / or spun prop?

If you have a spare prop, put it on and see if it happens. That will conform or rule out the prop. You may even be able to remove it and inspect the hub to find the problem.

The engine coupler is another story, and unfortunately, that's what it sounds like to me. Short of pulling the drive and inspecting the coupler and splined shaft, I don't know how else to do it.

Have a look at your engine mounts, where they are attached the the supporting stringer/s. Often they will rot and the engine will sag and become misaligned.

 

[Fordiesel69]

Re: Merc 120HP engine coupler / or spun prop?

Oh, I will add that trimming down the drive helped when it happened. I also throttled down from 3800 down to 3400 and took it back to the dock and it never reoccured.

Will take a look at the mounts tonight. I can;t beleive a little whimpy 120HP could ever hurt its own coupler. A V8 for sure, but a little 4 banger?

If it is the coupler, how can I reproduce it to happen again. Basically if there is a problem, I want it to break now so I can fix it over the winter.

 

[dubs283]

Re: Merc 120HP engine coupler / or spun prop?

its not the power of the engine that destroys a coupler,

its lack of maintenance

check your prop first, wouldn't be surprised if thats the culprit

 

[Bt Doctur]

Re: Merc 120HP engine coupler / or spun prop?

Once a coupler strips, it done. I`d suspect the prop.

 

[45Auto]

Re: Merc 120HP engine coupler / or spun prop?

I very seriously doubt if it's your engine coupler or prop hub causing the engine to rev and vibrate, then start working again. Once they start slipping they never "fix their self" and get better.

 

[elkhunter338]

Re: Merc 120HP engine coupler / or spun prop?

It is not the engine coupler. Engine coupler is a set of splines that are metal, one it spins you are dead in the water. Case in point 3 years ago I spun a coupler 8 miles out in the ocean. It spun and within seconds I no power.
I have heard props will slip at high torque and you can back off the power and get home sometimes.
If you have never done it you need to check engine alignment and grease your drive splines. Also check to see if they look worn, if worn replace coupler and driveline.

By the way if anyone needs an old style couple I have a good one.
About 30 hrs after replacement, I lost my engine timing gear and replaced the engine with a 2007. The 2007 took a differnt style coupler.

 

[Fordiesel69]

Re: Merc 120HP engine coupler / or spun prop?

Guys, I have a big big problem!!!!!

I took the outdrive off to inspect the splines, and found no damage at all. The problem is I cannot get the outdrive back on. It is not going in far enough. I bumped the engine over thinking it is like a transmission and just need to mate, but it did no good. Any ideas what I am doing wrong. I have tried putting the shift cable in each postion, forward, neutral, and reverse, and it did not help.

BTW, the book will not open on my computer. It was over 1GB to download and it says its corrupt.

 

[elkhunter338]

Re: Merc 120HP engine coupler / or spun prop?

How far on is it going?
I have had my 140 hp off several times.
1. make sure you are in forward gear with your boat shift lever.
2. make sure your outdrive is in forward gear, you will need to hold tension on the prop to keep the outdrive fully engaged in forward gear.
3. this is so the shift levers mate
4. recommend two people maybe three
5. With the old style engine coupler which yours should be if you have not switched to a 1 piece rear main seal and a new flywheel.
I had to have someone in the boat to help guide the drive line into the splines. Tight reach
Otherwise the drive would not go on.
Also since you moved the engine the splines will no longer match up or if you turned the driveline on the outdrive.
So when you get it in you might have to turn the prop some to get the drive line to move alittle for the splines to mate.
Make sure and grease the splines, clean all the old grease off. Merc has a spline grease but not sure how critical it is to use the marine spline grease. It should slip in easily when everything is lined up.