Another Post about possible coupler failure?

[ultrarunner]

2003 Mercruiser 3.0 with Alpha Drive with about 30 hours total since new...

Spent the last two evenings reading every post I can on the symptoms.

History: Buddy bought boat new and used it a couple of times at Lake Shasta in the first two years. I bought it because my old Trusty 35 hp Lark Evinrude was no longer welcome at my old California stomping grounds after 50 years.

Nieces and Nephew pestered me about getting out on the water and last weekend was the first time the Mercruiser has been out of the garage in 4 years.

First 20 minutes it runs like a champ... never went WOT... but moved right along between 3000 and 4000 rpm.

Decide to head back to the Dock and it starts having symptoms like the clutch is slipping in a car.

Starts OK... will not go above 2000 RPM without engine revving and hull speed dropping...

Things Checked:

Made sure drive was down and didn't just go by trim indicator.

Took Prop and Plastic Bushing into Prop Shop and was told it's not the problem

Put Drive in Forward and with my hands was able to turn prop which turned motor... at least until I hit compression stroke.

Don't want to believe it's the coupler with only 30 hours and no Prop damage

One more thing... when exceeding 2000 rpm the boat would slip and I could feel a deep thumping vibration... would have to drop down to around a 1000 for drive to stop "slipping" and "catch". Motored back to Discovery Bay at 5 to 7 mph.

Service History... 20 hour service done at Dealer...

Dealer suggested sea trial and has salt water dock. Boat and trailer never exposed to salt water... so I didn't want to do that. Plan to keep it at least as long as my 57 Fiber-Flite Sportsman and Lark 35.

Is next step pulling the motor?

 

[mylesm260]

Re: Another Post about possible coupler failure?

Not the motor, but the drive.

You can look at the splines on the drive-shaft to the drive, and check for any damage, or signs of coupler damage.

Removing the drive isn't actually that big of a deal, it can be done in about 30 minutes with a manual and the right tools.

 

[jd_1598]

Re: Another Post about possible coupler failure?

N/A

 

[Bondo]

Re: Another Post about possible coupler failure?

Not the motor, but the drive.

You can look at the splines on the drive-shaft to the drive, and check for any damage, or signs of coupler damage.

Ayuh,... The Drives gotta come off 1st,..
The splines on the input shaft should show Damage if the Coupler is gone..
Also,...
Check the Alignment before you pull the motor,... Just for diagnostic purposes..

 

[P 0 P E Y E]

Re: Another Post about possible coupler failure?

The coupler fails at the rubber to metal bond and does not necessarily show visual signs of slippage, When it fails. (or it used to back in the day)

I would suggest you inspect your gear case oil for chips and chunks first.

See if the shif cable is properly adjusted

Then remove the drive and check input shaft and coupling area for damage, malfunction or wear.

 

[Bt Doctur]

Re: Another Post about possible coupler failure?

Never had any with reported noise so I`d check the oil level in the drive too.
If not up to the level hole ,pull the top cap and look inside.

 

[ultrarunner]

Re: Another Post about possible coupler failure?

Thanks guys for the replies

I've been reading and re-reading the factory manual and the plan is to take a closer look this weekend.

Also ordered the Clymer Manual the other day and waiting for it to arrive.

Always do my own maintenance and repairs on every car I've owned... looks like it's time to get my feet wet with the Mercruiser.

Here's a related question that probably should be in a new thread...

Am I being overly cautious by keeping my boat Fresh Water only?

The selling dealer offered to take a quick look if I would put in the water at his saltwater dock.

 

[dan t.]

Re: Another Post about possible coupler failure?

salt water will do no harm, thats what anodes are for, just flush it out after it comes out of the water

 

[MikDee]

Re: Another Post about possible coupler failure?

Thanks guys for the replies

I've been reading and re-reading the factory manual and the plan is to take a closer look this weekend.

Also ordered the Clymer Manual the other day and waiting for it to arrive.

Always do my own maintenance and repairs on every car I've owned... looks like it's time to get my feet wet with the Mercruiser.

Here's a related question that probably should be in a new thread...

Am I being overly cautious by keeping my boat Fresh Water only?

The selling dealer offered to take a quick look if I would put in the water at his saltwater dock.

It's salt water, not battery acid! Jeez, Gimme a break
I've lived with it my whole boating life, never knew anything else growing up on L.I. Yeah, things will corrode faster, but they're not gonna disintegrate before your very eyes, and for a test ride, a quick flush afterward, and you'd never know it was even in there.

It's not just you, so many people think salt water is so bad, I'm tired of hearing it, it's not as bad as you think, and actually preserves wooden boats better then fresh water, and yes, it sounds like your coupling is bad, been there, done that, maybe the alignment was off for some reason, & it wore out, or the boat was way overloaded, or lugged?

 

[ultrarunner]

Re: Another Post about possible coupler failure?

No overloading or lugging on my end... only had it out 20 minutes in total before problem.

Previous owner did pull his kids around tubing on Lake Shasta for a day...

Alignment Tool Question:

OEM tool comes with several pieces and aftermarket usually is only the shaft... Is OEM with the adaptor the way to go?

 

[ultrarunner]

Re: Another Post about possible coupler failure?

It's salt water, not battery acid! Jeez, Gimme a break
I've lived with it my whole boating life, never knew anything else growing up on L.I. Yeah, things will corrode faster, but they're not gonna disintegrate before your very eyes, and for a test ride, a quick flush afterward, and you'd never know it was even in there.

It's not just you, so many people think salt water is so bad, I'm tired of hearing it, it's not as bad as you think

Good to know... my 1957 runabout has spent 50 years at Lake Tahoe and I've been told by many the only reason it has survived in such great shape is because it's never been in salt water...

I tend to keep things a very long time... bought a Model A Ford in High School and I still have it...

Appreciate the help...

 

[Glastron_V210]

Re: Another Post about possible coupler failure?

I'd sure do the nail polish trick on the prop before I took anyone's word on it that the prop is ok.

Paint a line from the prop nut to the prop. Run the boat until you get a spin, then check the prop...if out of allignment it's the prop. Confirm this before wasting your time pulling the drive/engine etc.


Pushing the prop by hand means nothing, (If it was a good enough test the coupler would have spun on your test when the engine hit compression) and I have no idea how a prop shop can tell you with any certainty that it's not the prop.

Chay

 

[sdoomaha]

Re: Another Post about possible coupler failure?

Starting with the simpler things.....do you have a hydrofoil on the boat? If so remove it and try it without. My old boat had a hydrofoil and it caused MAJOR prop slippage once up on plane. Removed it and problem solved.

Good Luck.

 

[ultrarunner]

Re: Another Post about possible coupler failure?

Starting with the simpler things.....do you have a hydrofoil on the boat? If so remove it and try it without. My old boat had a hydrofoil and it caused MAJOR prop slippage once up on plane. Removed it and problem solved.

Good Luck.

No Hydrofoil... everything looks OEM just like the pictures in the Mercruiser Manual... thanks for the suggestion.

I would do the nail polish trick... it's about 3 hours plus to get to the launch, launch and get back home.

The shop looked briefly at the Prop and asked if it is new and carefully examined the torque sleeve and couldn't find any sign of slippage or fracture.

I order a spare prop and should have it in a few days... otherwise, I would have tried that.

Someone suggested going to a shop with a Dyno for Stern Drives... is this something all Mercruiser Certified shops will have on hand?

 

[ultrarunner]

Update ***

Update ***

I took the boat into a local Mercruiser Dealer and they tested it on a dyno...

They were unable to duplicate the problem and boat ran fine through all rpm ranges without slipping. Mechanic commented on showroom condition of the engine bay, fluids and motor.

So the good news is the coupler and prop bushing check-out OK

I still don't know what caused the original problem.

Mechanic did find the trim indicator was off by about a third...

Thanks again for everyone's assist... anchor away!

 

[dutch135]

Re: Another Post about possible coupler failure?

If the trim indicator was off, and you were using that to set your trim,
maybe the lower unit was trimmed up higher than you thought, and
you were aerating the prop? I had that type of problem on an
outboard boat i had due to the prop being so much closer to
the surface, which isn't typically a problem in an I/O.,
or, maybe there is another prop problem , causing that aeration/caviation.
it would seem that something like that wouldn't just change
during the middle of your trip unless you had a prop strike
or something..
certainly try that new prop pronto, to eliminate that
as being the trouble spot..

 

[ultrarunner]

Re: Another Post about possible coupler failure?

If the trim indicator was off, and you were using that to set your trim,
maybe the lower unit was trimmed up higher than you thought, and
you were aerating the prop? I had that type of problem on an
outboard boat i had due to the prop being so much closer to
the surface, which isn't typically a problem in an I/O.,
or, maybe there is another prop problem , causing that aeration/caviation.
it would seem that something like that wouldn't just change
during the middle of your trip unless you had a prop strike
or something..
certainly try that new prop pronto, to eliminate that
as being the trouble spot..

Thanks Dutch

I ordered a new Prop through iboats.com... I should have early next week along with a floating prop wrench to do a proper field test.

It's still a mystery... but at least I've eliminated the drive coupler

 

[ultrarunner]

Re: Another Post about possible coupler failure?

Two pictures of the Drive...

 

[MikDee]

Re: Another Post about possible coupler failure?

Maybe you picked up a plastic bag, or piece of rope on the prop. you said you heard thumping. Does the boat still act this way?
By the way, What is that plate bolted on the drive?

 

[ultrarunner]

Re: Another Post about possible coupler failure?

Maybe you picked up a plastic bag, or piece of rope on the prop. you said you heard thumping. Does the boat still act this way?
By the way, What is that plate bolted on the drive?

There is a zinc plate on the drive between the stern and the drive... is this what you see?

This is my first I/O... I know the unit is as delivered... but I don't know if the plate is OEM or Dealer installed... here's a close-up and I just verified its attached to the case...

The Dealer didn't mention anything about it yesterday...

My prop also has several impression on the leading edges from when they removed it and put it back on... didn't have any before taking it in... you can see one as the edge "bright spot" in the close-up picture.

OFF TOPIC... my boat with 30 hours on the hobbs meter now shows almost 60 hours... Dealer left the key on for 29 hours