Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

[Mike59]

I have a Celebrity 290 with Mercruiser 5.6L with Alpha 1 I/O drives. At approximately 2700 rpm the propellor disengages. Checked the prop and its fine. When I try and turn by hand in fwd it disengages. In reverse its fine. Is ther a linkage I can adjust or is the problem in the drive. Any ideas would me much appreciated.

 

[Bifflefan]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

While you didnt post the year of the boat, Id guess that the lower shift cable needs adjusted.

You will need to get a manual and read it then adjust it.

 

[Blk-n-Blu]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

with the drive down and in forward gear the prop should lock CCW and spin free CW possibly with a clicking sound.
In reverse it should lock CW and spin CCW.
You may have a spun prop hub.

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

The boat is 1990. Thanks for the info

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

Prop is fine. I replaced with new as a safety precaution.

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

Carried out adjustment and fault reoccurred. Any other ideas?

 

[Brentathon]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

I remember that I thought my drive was disengaging............and it turned out that my "diffuser ring" on the aft end of the propeller hub fell off.....which allowed exhaust gases to enter into the blade area, giving the feeling that I was "free wheeling".

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

Carried out sea trial, slowly increased to 3000 rpm and then disengaged. Went back to neutral increased rpm and immediately disengaged. Triied again and disengaged at 2800 rpm. Problem is intermittent. Compared left engine and it was steady up to max rpm. Replaced both props and inspection of spline was good.
Any more thoughts??? before I cancel my holiday?????

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

After much research I believe it could be the coupler unit. Will advise what I find.

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

Removed the drive. Inspected housing no rubber shredded from the coupler. Installed alignement tool and not out of alignement. Shift cable is not stiff and adjustment was correct.

Could it still be the coupler or should I investigate the drive for the problem?

 

[Mike59]

Re: Mercruiser 5.6L with Alpha 1 Drive in Fwd Intermittently disengages at high RPM

Noticed when taking for haul out that even at low RPM no thrust although when throttle put forward it ratcheted into gear.
Appreciate any comments if you still feel that the problem is still the coupler or should look at upper/lower unit.

Thanks