2001 wellcraft 270 costal powered by a mercruiser 7.4 mpi with a bravo 3. Doesn’t accelerate.

[Cruis]

Hi everyone, I have a 2001 wellcraft 270 costal powered by a mercruiser 7.4 mpi with a bravo 3 prop pitch 22. This summer the boat ran great no issue at all coming later in the season I noticed that at 3000 rpm the engine will rev to 3200 rpm on its own and gain no speed. When that happens I give it more throttle to 4,000 rpm and still gains of speed it actually slows down and you and hear that the engine sounds a bit louder I believe it’s because the boat isn’t gaining speed but the engine is running to its rpm.
Another day the boat was running at 3200 rpm getting 18 mph as usual but the more I open the throttle the boat slows down instantly and the loud engine sound comes back. Normally with 1/2 tank of gas at 3800 rpm I would get 23 -24 mph this is at the beginning of the season.

I took off the prop and inspected it. I also cleaned it and put it back on but that wasn’t the solution.
I checked for any code on the engine nothing.

Dose anyone have any ideas of what’s going on?
Thanks

 

[dubs283]

Engine coupler hub failing?

 

[Cruis]

Engine coupler hub failing?

That was a thought but, no burning rub smell and feeling the coupler the rub had no broken pieces. Also I would also think that the coupler will fail or work due to it being rubber once spun out always spun out.
I was thinking if my hull has grass but I’m not sure if that would have such an impact. The boat was driven every week but I did noticed that after skipping a week of boating I noticed this problem.

 

[QBhoy]

Got to be the coupler surely. Are the props hard splined like usual ?

 

[Cruis]

Got to be the coupler surely. Are the props hard splined like usual ?

Yes, The splines are built with the prop and they are in good shape.
How can I be sure it’s the coupler ?
I tried full throttling it and the max rpm is the same are before it sits around 4500 -4600.
I would think the rpm would go higher if the coupler is slipping. Don’t you think?

These are my assumptions
Clutch slip- but I believe once it engaged it stays engaged.
cavitation/ventilation of the prop- not sure why this would happen now because before the boat ran good.

I appreciate the thoughts

 

[Scott Danforth]

check drive fluid level. check for burnt fluid. you could have burnished cone clutches

 

[QBhoy]

Yes, The splines are built with the prop and they are in good shape.
How can I be sure it’s the coupler ?
I tried full throttling it and the max rpm is the same are before it sits around 4500 -4600.
I would think the rpm would go higher if the coupler is slipping. Don’t you think?

These are my assumptions
Clutch slip- but I believe once it engaged it stays engaged.
cavitation/ventilation of the prop- not sure why this would happen now because before the boat ran good.

I appreciate the thoughts

I’d think all mpi would have a limiter. You’re probably hitting that.
You’d assume it can only be the coupler or the drive cone clutch is slipping…possibly caused by water in the oil perhaps

 

[Cruis]

check drive fluid level. check for burnt fluid. you could have burnished cone clutches

Hi, Scott
For the past 2 months I have added a quart of gear lube. I always kept the reservoir topped off. I asked a mechanic about it but, he said it could be a seal and I can change it next season as long I kept the reservoir topped off.
I think it's the upper seal because I can see the gear lube dripping from the gimbal bearings.

Could this cause the cone clutch to burn ?
Also out of curiosity how does a burned cone clutch cause partial slipping?

 

[Scott Danforth]

Hi, Scott
For the past 2 months I have added a quart of gear lube. I always kept the reservoir topped off. I asked a mechanic about it but, he said it could be a seal and I can change it next season as long I kept the reservoir topped off.
I think it's the upper seal because I can see the gear lube dripping from the gimbal bearings.

Could this cause the cone clutch to burn ?
Also out of curiosity how does a burned cone clutch cause partial slipping?

yes, if the oil level dropped too much, you would burn out the cone clutch.

 

[QBhoy]

Hi, Scott
For the past 2 months I have added a quart of gear lube. I always kept the reservoir topped off. I asked a mechanic about it but, he said it could be a seal and I can change it next season as long I kept the reservoir topped off.
I think it's the upper seal because I can see the gear lube dripping from the gimbal bearings.

Could this cause the cone clutch to burn ?
Also out of curiosity how does a burned cone clutch cause partial slipping?

There’s your answer right there.

 

[Cruis]

yes, if the oil level dropped too much, you would burn out the cone clutch.

I knew I should have changed that seal.
Would I be able to run the boat like this for the rest of the season?
Lastly would the burning of the cone clutch cause the boat to delay shift into gears because the boat shifts into gear instantly only thing is I get a slight knock going into forward gear and reverse is smooth.

 

[Scott Danforth]

I wouldn't run it

I would pull the drive and go thru it

 

[Cruis]

I wouldn't run it

I would pull the drive and go thru it

Ok, would I smell the burnt fluid or will I see the damage on the cone clutch?
If so should I just replace it?

 

[Cruis]

There’s your answer right there.

Thanks, I’ll check the problem out once I pull the boat out. I really hope that’s my problem.

 

[Cruis]

I was thinking and thought can the lower shifting cable not be adjusted properly causing the cone clutch to slip under load ?

 

[Scott Danforth]

I was thinking and thought can the lower shifting cable not be adjusted properly causing the cone clutch to slip under load ?

it may

however once a cone clutch starts slipping, it burnishes itself

 

[Cruis]

it may

however once a cone clutch starts slipping, it burnishes itself

Ok, Last weekend I took the boat out for a test drive to narrow things down and I noticed when I slowly back the throttle off to 2000rpm. I get a sudden vibration that last about 5 seconds. Can it be related to the clutch?
Narrowing my problems
- not the coupler
- possibly the cone clutch

 

[alldodge]

Keep adding gear lube and lube leaks into the bilge
Seal and upper bearing problem
Want to keep running it until the end of the season

Might be able to save something to rebuild if done now. Don't seem to care so run it until it breaks. New drive cost 10K, its only money

 

[tpenfield]

My thoughts . . .

- That is a big/heavy boat for a single engine, even a 7.4 . . . So, lots of load on the outdrive/engine.
- Being a 2001 . . . probably 310 HP and running the MEFI-3 controller
- I tend to agree maybe more the outdrive rather than the coupler. If it were the coupler, I'd expect it to fail more completely and quickly.
- The clutch is in the top of the drive, and if you are loosing gear oil, then the clutch could be burning/glazing.

I'd pull the drive and see what you discover . . .

 

[tank1949]

That was a thought but, no burning rub smell and feeling the coupler the rub had no broken pieces. Also I would also think that the coupler will fail or work due to it being rubber once spun out always spun out.
I was thinking if my hull has grass but I’m not sure if that would have such an impact. The boat was driven every week but I did noticed that after skipping a week of boating I noticed this problem.

hub may be slipping?