Lost most of prop power

[Don S]

Re: Lost most of prop power

This thread is getting silly. Use some deductive reasoning.

You may have stripped the upper gears in your outdrive..

If that happened, it would overheat because the raw water pump was not working. Why, the gears are stripped and won't turn the pump.

While pulling a tube rider at about 3,000 rpm, we heard a clunk and saw and smelled smoke from the engine compartment.

Checked the compartment for visible clues and found none. Guages all read normal. Fluid reservoirs were all normal.

The unit would shift into

Here are the details to expline why the coupler is at fault.

Smoke is from the outside of the couple spinning faster than the inside. They are held together by rubber. You have rubber to rubber burning at high loads and rpm.
If the prop spun (It would act the same) you woundn't smell rubber burning. It's under water and staying cool.

Gauges read normal, and boat would move at low rpm. That tells you the upper gears and splines in the coupler are ok. Because the raw water pump in the drives lower is still turning and coolling the engine.

Now the fun part.

My prop spins easily in forward gear or neutral with the engine off.

Could be a bad prop, what happens in reverse?????? Is there more resistance when turning the prop in forward than in neutral???? Can you turn it easily both directions?

If it was the prop, then why the smoke and burned rubber?

 

[solar7647]

Re: Lost most of prop power

Just my quick two cents, your previous post said you where running a stainless prop when this happened. Was there any kind of damage to it? It Probably wont look like much but as a stainless prop dosnt bend or break as an aluminum one would since it is much harder.

It sounds to me as if you hit a submerged object and since the prop has no give it caused internal drive damage. I would think purhaps the prop shaft or one of its componets in the lower unit was damaged. As you can see in the photo there is a lot in there to break. It could have cused the engine to back fire and causing the smoke.

I have struck a large submerged log before and it had a large bang and the engine back fired and stalled and there was smoke from that. I have a smaller, older engine then yours and such a sudden stop caused it to stop but I think a new set up like your wouldnt completely die as mine did.

Coupler failure is most offten caused by miss aligned engine right (?), by ether someone pulling it and not lineing it back up or by the mounts slowly lossening and considering the age of the boat it dosnt seem that would be an issue yet, not to say it couldnt be it just dosnt seem old enough for that to happen to them yet.

I also would not suspect the upper unit yet ether just because my train of thought is the problem started at the prop so damage would be mostly to the lower unit.

 

[Cptkid570]

Re: Lost most of prop power

I'm just trying to come up with possibilities and areas to be checked. It definitely makes sense for it to be the coupler.. with the smoke and everything...

I guess I need to ask if you drew the line correctly or not.. What exactly did you draw the line on? The line needs to be on the driveshaft and the coupler (place where the driveshaft goes in). You'd indicated that you had a hard time getting back there..so, what makes you confident that the line is correct?

Don S. - good point about the overheating... but, if the driveshaft at the coupler doesn't spin, the impellor still wouldn't spin (outrdrive has to spin for the impellor to spin). and, either way, if he is getting 2mph, then something is spinning a little bit. What if it were the lower gears in the outdrive, wouldn't the impellor still spin?

All I am saying is that it's either the prop (most likely not if it does the same thing with a different prop), lower gears, upper gears, or coupler.. Not much else it could be... IF the line is drawn right and IF the coupler is not the issue, then wouldn't you want to check the gears?

Don't get me wrong, I think it's probably the coupler... I'm just trying to point out other possibilities.

 

[Don S]

Re: Lost most of prop power

Don S. - good point about the overheating... but, if the driveshaft at the coupler doesn't spin, the impellor still wouldn't spin (outrdrive has to spin for the impellor to spin). and, either way, if he is getting 2mph, then something is spinning a little bit. What if it were the lower gears in the outdrive, wouldn't the impellor still spin?

The seperated rubber in the outer and center parts of the coupler still has enough friction in it to operate the drive at low rpm.
You have to understand how these things are made, and how they work to know what happens when they fail.
There are 2 ways for a coupler to fail. The rubber between the inner and outer portions of the coupler, or the splines the outdrive splines go into can wear away from lack of lubrication. Then nothing turns but the coupler. Engine overheats, and it doesn't move at all.

 

[deandec]

Re: Lost most of prop power

Is the coupler/shaft line drawn correctly:

I believe so. I now know what a coupler looks like. I can see the shaft and coupler spinning when in gear on the hose. I can reach the coupler and shaft with my hand through the transom cover opening. I painted the line from shaft up and over the coupler.

The paint line remained matched after putting in gear under load. If the shaft was spinning in the coupler, the lines would have separated. (Similar to a loose drill bit in its coupler?)

There is now zero thrust from the stern drive.

The propeller spins clockwise with the engine off when in forward and counter clockwise in reverse. It will not spin in the opposite relative directions.

when in gear under load today, there was a new and significant moaning sound from the drive train.

When operated after the initial event for 20 minutes at 2 mph the engine gauges read normal. All fluids were normal. There were no unusual operational sounds.

I can see no distorted materials at the coupler/shaft when looking down at it with a spot light

All my tests have been run with a propeller that was not part of the initial event and which worked well at last use.

I have yet to remove the stern drive because I am not sure what seeing the drive shaft will tell me. But, it is on my Sunday agenda.

What might I learn from pulling the Stern Drive?

Will I be able to see the coupler damage?

Will the drive shaft splines evidence damage?

Thanks to all who are trying to help me diagnose this problem.

Dean

 

[cr2k]

Re: Lost most of prop power

What I have seen happen that shared symptoms:

A spiral or diagonal break of the vertical drive shaft above the pinion. At low power the shaft would turn the pinion creating some propeller movement.

Impeller was still turning due to the fracture being below the impeller.

I still believe it's the engine coupler, otherwise why would there be smoke?
The impeller would still turn in neutral and then enough at low power to cool engine.

Besides the deductive reasoning flow chart sez so.

Stick your hand (engine off) in to the engine coupler and touch it. If it comes back with some nasty crap that takes you 3 days to get off your hand; I will bet a pay check it's the coupler.

 

[deandec]

Re: Lost most of prop power

"Stick your hand (engine off) in to the engine coupler and touch it. If it comes back with some nasty crap that takes you 3 days to get off your hand; I will bet a pay check it's the coupler."

I have run my fingers around the coupler and shaft to learn the shapes and to see if I could feel some fragmented material surfaces. All was smooth and no residue or grease came up on my hand.

 

[deandec]

Re: Lost most of prop power

New information perhaps.....

I found a zerk on the coupler shaft. I have read that there is a sealed coupler used on Gen II outdrives that has a zerk for greasing the splines.

I think that means that I drew a paint line on the coupler shaft, not the drive shaft.

So, it would seem the paint line test will not work to determine that the coupler hub is slipping???

That also would mean I cannot visually see the inside of the coupler by pulling the stern drive, nor can I see the drive shaft from inside the boat??

Does that put a different "spin" on things?

Dean
2000 5.7L Mercruiser w/Alpha One Gen II

 

[dirtyoldman]

Re: Lost most of prop power

New information perhaps.....

I found a zerk on the coupler shaft. I have read that there is a sealed coupler used on Gen II outdrives that has a zerk for greasing the splines.

I think that means that I drew a paint line on the coupler shaft, not the drive shaft.

So, it would seem the paint line test will not work to determine that the coupler hub is slipping???

That also would mean I cannot visually see the inside of the coupler by pulling the stern drive, nor can I see the drive shaft from inside the boat??

Does that put a different "spin" on things?

Dean
2000 5.7L Mercruiser w/Alpha One Gen II

I think you've discovered the solution here. The coupler is about the only thing that makes sense.

 

[deandec]

Re: Lost most of prop power

I agree. I have scheduled with a pro to diagnose and repair.

This forum helped me to expect an engine removal and coupler change in advance.

Thanks to all.

Dean

 

[nola mike]

Re: Lost most of prop power

this is sounding harder than it should be, especially that whatever it is now seems completely broken. is the driveshaft turning with the engine running? if no, then it's your coupler. if yes (but the boat still isn't moving), then your problem is somewhere else.

 

[dirtyoldman]

Re: Lost most of prop power

this is sounding harder than it should be, especially that whatever it is now seems completely broken. is the driveshaft turning with the engine running? if no, then it's your coupler. if yes (but the boat still isn't moving), then your problem is somewhere else.

He is saying he can't see the driveshaft.

 

[Cptkid570]

Re: Lost most of prop power

Please keep us posted on what your mechanic finds.

 

[deandec]

Re: Lost most of prop power

Well, I took the boat to the lake one more time without an assistant.

Remember, this coupler appears to have a female shaft with a grease zerk on it which obscures the male drive shaft

In neutral, I can see the coupler and coupler shaft spinning.

In forward at 1500 RPM, I can see the coupler and coupler shaft spinning.

Also the alternative prop puts out a weak "jet" stream behind the boat.

But...now there is a loud continuous groan noise in forward or reverse gear above 800 rpm from the rear of the boat. I was not able to identify the source nor did I want to let it continue for long on the three attempts in forward gear.

At the first incident and during the first trailer test, there was no abnormal sounds. When on the hose, in gear, at 2000 rpm there is no groan noise.

 

[MikeyBoyAz]

Re: Lost most of prop power

So, I know this topic was started by someone else, but heck... Today I was out on the lake with family enjoying some wakeboarding with my 305, and I heard a pop, engine revved and smoke billowed out the bilge blower that was rubbery and oily smelling... prop turned weakly when in gear, thrust was very faint, and the engine started warming up a little but not much above normal running temp... Took my 2 minutes on this site, dang do I love it... but... I think it is going to suck bold getting it replaced, even if I do it myself... B.O.A.T. Thanks all for your implicit help!

 

[deandec]

Re: Lost most of prop power

OP Here.

Mechanic says starboard front engine mount was "collapsed" . Port side was ok, so the coupler was spun due to misalignment.

They will pull the engine this coming week.

I had the boat trailer pop off the motorhome hitch just before the incident. The trailer tongue hit the ground hard enough to break a chain link.

Could that impact have affected the motor mount?

 

[solar7647]

Re: Lost most of prop power

OP Here.

Mechanic says starboard front engine mount was "collapsed" . Port side was ok, so the coupler was spun due to misalignment.

They will pull the engine this coming week.

I had the boat trailer pop off the motorhome hitch just before the incident. The trailer tongue hit the ground hard enough to break a chain link.

Could that impact have affected the motor mount?

yes, i would think it is possible. at least it didnt help any.

 

[jason32038]

Re: Lost most of prop power

How much are they chargin you??

 

[Bondo]

Re: Lost most of prop power

I had the boat trailer pop off the motorhome hitch just before the incident. The trailer tongue hit the ground hard enough to break a chain link.

Could that impact have affected the motor mount?

Probably Not.... It's usually Rotten Wood that causes that....

 

[deandec]

Re: Lost most of prop power

Probably Not.... It's usually Rotten Wood that causes that....

Hmmm....fiberglassed trailer boat, stored in garage, 10 yrs old. No water in bilge when moored for a few days. I have not seen any structural wood exposed, but I guess anything is possible.