85 75 HP Merc OB PTT diagnostics

[nos440]

I have a 1985 75 HP merc In line 4 cyl. The PTT is not working. The selenoids both click and send 12.7VDC to the PTT motor. Does this mean the $300 PTT motor is bad? Can it be rebuilt or must I shell out the big bucks?

Any reason I can not use the motor without it for the time being? It releases just fine with the bolt/screw in the side of the PTT so can adjust the trim with the rod. Should I leave it free to tilt or slide the rod through the provided locking hole so the motor can not tilt at all for temporary use? Seems to me you would want it free to tilt if you hit something but backing up might be a carefull low RPM process like that. Now that I think about so would slowing down. Maybe it needs to be locked.

Thanks Craig

 

[Faztbullet]

Re: 85 75 HP Merc OB PTT diagnostics

If it has the internal 3 ram trim it is best to replace it with a pump and motor assy as it runs less noisy,lower amp draw and faster trimming. The Prestolite and Eaton motors are NLA from Mercfor this model trim. I use the MES brand part # T1083M on my customer units.

 

[mke039]

Re: 85 75 HP Merc OB PTT diagnostics

I had the same problem. If your PTT has not been used in a while, the armature often get corroded up...there is a simple fix (if you are somewhat handy)

Take the unit off. Take the motor apart. Hold the amature in the index fingers of your left and right hand so it can spin. Hold the windings to a bench grinder with a wire wheel attached. Allow the wire wheel to buff the windings. Be careful as the armature will spin very fast in your fingers. Let it spin down, replace. The brushes are kind of tricky to get back into place, but if you reinstall correctly you have just saved yourself a small fortune.

Unless the windings are broke...which is rare...this should solve the continuity problem.

 

[nos440]

Re: 85 75 HP Merc OB PTT diagnostics

The guy I bought the boat from had not used it since he bought it a year ago and I suspect it was not used much by the guy he got it from recently. The symptons the guy I bought it from was. It was working and just stopped all the sudden and never worked again.

I'll give that a whirl either way it has to come off to fix it. Any tricks to getting it off?

Craig

 

[nos440]

Re: 85 75 HP Merc OB PTT diagnostics

If it has the internal 3 ram trim it is best to replace it with a pump and motor assy as it runs less noisy,lower amp draw and faster trimming. The Prestolite and Eaton motors are NLA from Mercfor this model trim. I use the MES brand part # T1083M on my customer units.

Again thanks for your earlier help on this Trim problem. I'm fairly sure that I'm just going to invest in this new MES T1083M replacement you suggested. Do you happen to sell this unit? If so I'd like to patronize you since you provided the suggestion. Could I possibly get you to elaborate on the method to get the old trim motor out and new one in? I understand if you would rather not share trade secrets. So if that is the case just say so no hard feelings will be the result.

Thanks Craig