Help with Electramatic slipping

[royal0014]

Johnson Super Seahorse Electramatic 40hp, RK-28B (1966)

Wrote here about taking the boat out for the first time on Father's Day and the hub slipping. At least that's what I thought/hoped it was. No such luck

Bought a brand new prop for it and put it on yesterday. Have new thrust washer, drive pin, and cone ordered, but hasn't came in yet. Took it out today for a little fishing with my son. As soon as I gave it the gas it slipped and revved up high (insert foul words here...)

Well, I kept trying. If I eased into the throttle real slow, I could get the RPM's up. It would slip again a couple times, but I eventually got WOT and on plane. Ran along great for a minute or two, then suddenly turned loose, no forward momentum and RPM's shot way up. Throttled back down and kept trying. It would slip again, I would just keep easing up until it got on plane. Went through this scenario several times.

On the prop I went from a 10 3/8 x 11 1/2 to a 10 1/2 x 12. Don't think that matters, 'cause it acted almost the same with both props. I forgot to mark the new prop to check for slip. Also, after running a bit and seeing how it planed, I moved the trim pin from the second hole out to the first hole, nearest the transom. Helped get the bow down a little, but not much. Seemed to make it slip more.

Arrggg, this is aggravating. I don't want to put $500 worth of clutch hub and shaft spring in it

Any ideas?? I'm going to open up the top vent plug and make sure the gearcase is full of oil. I have not seen any oil leak.

Sorry for the long post, and thanks to all

 

[F_R]

Re: Help with Electramatic slipping

Has it worked on the boat before? Thinking about installation here (too high). Whenever a slipping clutch is suspected, you should ALWAYS check it out electrically before assuming it is the clutch.

 

[royal0014]

Re: Help with Electramatic slipping

Dont know about before, nothing was working when I got it three years ago. It had been pretty well butchered.

The top of the cavitation plate is about two inches below the hull. If it was cavitating, I wouldn't think I would have to shift to neutral and wait for the RPM's to come down. It will slip from dead still.

I suppose I could have a not so good connection at the control. I'll check that out, too.

It's definitely is not a gear lube problem. Removed the top vent screw, it only took a couple of squirts and lube was running out. Using Citgo Marine Plus Type C lube.

Thanks again........

 

[royal0014]

Re: Help with Electramatic slipping

Well, it's been a month, but finally got to go out and try the boat again. Still no luck.

After my last outing, I managed to snap off the positive terminal on the starter (don't ask). Had to wait a couple weeks to replace it. At least it worked with no problems.

In the mean time, I went through the shift wiring, made sure it was all connected good. Tested at 7.6 ohms and full voltage from the battery. So I think I pretty well eliminated low voltage as the source of my problem.

So I took it out early this morning. And no change from last time. Still slipping. Seems to hold better after everything warms up, but still won't hold more than a minute or so. Was by myself this time; without the weight of a passenger, it doesn't get a on plane easily.

At least one thing went right. Had to plug one of the tires on my truck in the dark last night, and it's holding air still