A 1987 Mercury 80HP Clutch Problem

[MotorboatMike]

Hello, Forgive me for being a noob at this but I was on the river and decided to give my boat full throttle and shortly afterwards it sounded like my prop left my boat ( without hitting anything ) and my engine acted like I was in neutral. I lowered the RPM's quickly by shifting to neutral, then shut off my motor to see if the prop flew off.

Nightmares of transmission gears danced through my head. Everything looked OK so I started the motor and it went OK at 75% throttle without incident for a mile or so until I took it out of the water.
I was glad it wasn't busted up, I thought well, I have to baby it now.
Tonight I was talking to a boating friend and he said it could be something as simple as adjusting the linkage on the clutch.
He said all I need to do is take the cover off the top of my motor to find it if my engine is anything like his.

Last year, this happened a few times even under a lesser RPM with another prop I was using so I thought that it was too loose and I put my spare on to use and it stopped happening until today.

I am fairly sure I have a 1987 Mercury OB with 3 cyl. Auto Oil injection motor.
Good direction, jpg images, or webpage links with pictures I could find or be shown would be great help.

I have little knowledge of what makes these motors go.
Thank you for your help.

 

[diaric]

Re: A 1987 Mercury 80HP Clutch Problem

most likely cause is that the motor is just a little bit too high. as your under load and approaching wot your prop looses its bite in the water from the turbulance passing under the hull. my old worn out prop worked great, but my two identical new ones would blow out with 2 adults on board as i was working toward wot. after lowering about 3/4" i haven't had a problem. not familiar with any drive system that involves a clutch

 

[MotorboatMike]

Re: A 1987 Mercury 80HP Clutch Problem

What is wot?
I don't think that you understand what this sounds like. RPMS are way up there, it is as if the the inside of my lower unit was going but the prop flew right off.
My boat is very heavy too, it takes awhile to get it up on top of the water. I don't think there's enough turbulance under there to cause what I think you are talking about. Even if I tilted my trim to bring the prop out of the water, I don't think it would sound half as bad as it does the way I am trying to describe.
Sound just like the shaft my prop on is not even turning, just the guts inside.
Also, this continues until I put it in neutral.
I do thank you for your response though, it made me think.

 

[redjmp]

Re: A 1987 Mercury 80HP Clutch Problem

Sounds like a linkage adjustment problem or a possible spun hub on the prop.
Next time it lets go just pull the revs down and see if the boat hooks back up and idles forward. If so its a spun hub. if not it has in fact jumped into neutral and you probably need to adjust the shifter cable linkage.
BTW WOT stands for wide open throttle.

 

[MotorboatMike]

Re: A 1987 Mercury 80HP Clutch Problem

Sounds like a linkage adjustment problem or a possible spun hub on the prop.
Next time it lets go just pull the revs down and see if the boat hooks back up and idles forward. If so its a spun hub. if not it has in fact jumped into neutral and you probably need to adjust the shifter cable linkage.
BTW WOT stands for wide open throttle.

I just had my spare prop rebuilt and it looks like new, nice and tight and splines look great on both brass hub and drive shaft so it must be the shifter linkage.
Where, do we usually find this adjustment, on the motor or on my throttle box?
Also thanks for the WOT info.

 

[MotorboatMike]

Re: A 1987 Mercury 80HP Clutch Problem

Every picture tells a story doughnut?

Well, I tried to make the adjustment on the bottom cable, took that nut off the top, but could not make the treads longer or shorter and did not want to break any plastic so I left it alone. I don't know what to do but maybe once somebody sees my images they will say .... ahhh! "I know the solution." and post it below. Thank you! Mike

Port Side Motor

HERE IS A CLOSER VIEW ( bottom rod is for Forward N and Reverse )

I think this is a 1987