Merc 75, high rpm, no power?

[Beene]

I have a 2005 Merc 75 4S Carb outboard.

Last season I was getting:
28mph 4500 rpm
20mph 3700 rpm
7 mph 1500 rpm

This season:
No holeshot at all
No torque
Top speed now 16mph @ 6000rpm
Speed at 1500rpm still 7mph

Have replaced prop, hub kit, thrust washer.... nil change.

Nothing I do seems to fix the problem.

Why are my rpms so high, but no thrust?
Engine seems to scream, rev limiter kicks in, but I am barely moving.
Lat year, if I rolled on the power, if you were not sitting down, you soon would be. Not so anymore.

Feels as though the engine and the prop are not really connected.

Any help would be greatly appreciated as this is most frustrating.

The motor starts and runs like a top. Quiet, smooth.... can't figure this out.

Thanks

 

[JB]

Re: Merc 75, high rpm, no power?

Sounds like something broke in the drive train. What does it do in reverse?

 

[Windykid]

Re: Merc 75, high rpm, no power?

Sounds like something broke in the drive train. What does it do in reverse?

Agree with JB, any unusual noises or grinding? Have you changed the lower unit lube, and what did it look like?

 

[Beene]

Re: Merc 75, high rpm, no power?

Works great in reverse, just like last season.

I went over anything I changed from last season, and the only thing I could think of, and does not make sense, was the trust washer.

I took it out, and now my 75 runs like a top again.
Top speed is back
Torque is back

Its all good.

I have no idea why that would be.

 

[tredragon]

Re: Merc 75, high rpm, no power?

If anyone knows the answer to why this would have caused this, it would be a useful thing for us all to know!