Mercruiser 5.7 shift failure?

[BuzzM]

This boat is a 1983 Sunrunner 245 with a Merc 5.7/ pre-alpha outdrive. I was running at 4200 r.p.m., no problems. Stopped the boat momentarily, & shifted to nuetral with no problems. When I shift back into forward, there is no engagment. Same with reverse. There is no obvious sign of something coming loose of the shift plate in the engine compartment. The towboat operator said he could hear it clicking like it was trying to engage, when I moved the selector. But there is not the usual solid feel when it goes into gear. I thought I smelled rubber, very faintly, so I suspected a spun prop or worse, a spun coupling. The towboat guy thinks the shift cable may just be gunked up. The boat stays in a slip and the shift cable was replaced prfessionally last year. Any thoughts? Serial 6817160, model 02608344.

 

[Bondo]

Re: Mercruiser 5.7 shift failure?

The fact that the cable was replaced Last Year,.....
A Problem There might be quite Premature,.......

Regardless,.... The boat Has to go onto the Trailer before any Real Diagnosis can happen.....

Once On the wagon, you can determine What's Moving,+ What Isn't........

Have you tried disconnecting the Lower Shift Cable from the Shift Plate,+ Seeing it can be "Manually" shifted,..??...

 

[Don S]

Re: Mercruiser 5.7 shift failure?

I guess we could guess all sorts of things, broken shift cable, spun prop hub, blown drive, but the fact is, you need to do some checking to find what your problem actually is. Was there any overheat problem now that it won't go? Any metal shavings around the coupler? Is the shaft in the coupler turning when the engine is running?
Disconnect the shift cable from the shift plate on the drive and see if you can shift it by hand, if not. Time to check deeper.
Check the gear lube. Pull the drain plug and see if there is metal on the magnet, water in the oil etc.
Pull the drive and check the shift linkage. It may be damaged.
It's just going to take some time to check and eliminate things till you find the actual problem.

 

[BuzzM]

Re: Mercruiser 5.7 shift failure?

Thank's for the suggestions. It seems odd that it was running fine all day, until I brought the boat to a stop. It
shifted out of gear into neutral without a hint of trouble. The problem did not surface until I tried to put it back in gear. I'll get her up on the trailer and start digging. I just hope this one doesn't break the bank. Enjoy your holidays.

 

[BuzzM]

Re: Mercruiser 5.7 shift failure?

I may have to change my name out of embarassment, but I owe it to the other forum members to reveal the rest of this story.After a couple of days gone on busienss, went back to the slip for a closer look at the boat. Raised the outdrive.. no prop! When I was being assisted by our towboat captain, we both saw the prop there! I put a new prop on & all is normal. I can only assume that the nut, spider washer, etc. had backed off somehow, and the prop was barely on, but was aft of the shaft splines, resting on the rubber prop bushing. During the towing procedure, I guess the prop slipped off. I have NEVER lost a prop in
30 years, but I guess that I did not have the tabs locked in the grooves.
New small problem, the up trim switch works intermittantly. I can raise the unit with the trailering switch o.k. Down works fine. I assume it is the switch itself. Did not find any exposed wiring in the throttle handle.

 

[Fishermark]

Re: Mercruiser 5.7 shift failure?

Never would have guessed the prop fell off! 8)

While the intermittent problem may be your switch, I would suspect that the trim limit switch on the outdrive itself is going bad. You might try bypassing it back by the transom and see if your intermittent problem goes away. If it doesn't, I guess the trim switch on your throttle lever is going bad, but if the problem goes away, that points to the outdrive trim limit switch.

 

[Don S]

Re: Mercruiser 5.7 shift failure?

An intermitten trim is usually the sign of a solenoid on the trim pump going bad. Can you hear it click?
Normally when the switch goes bad it's a total failure, not just intermittent.
Might also check all the wiring connections for corrosion.

 

[Fishermark]

Re: Mercruiser 5.7 shift failure?

Don - The only reason I thought of the trim limit switch is Buzz makes it sound like the trailer button works fine, while the trim switch works sometimes and sometimes not.