Omc electric shift slipping in forward gear

[Thane2012]

I have a 77 omc electric shift 235hp with a 351w. I have rebuilt my lower unit last year installing new bearings and new forward drive spring. Today trying to back out of my very very shallow slip we got stuck and tried to power out of it and started hearing a noticeable clicking sound while in forward gear. We got unstuck but forward gear had very little thrust and seemed to be slipping and clicking while I revved it up but we still moved slowly. Any thoughts? Spring broken again? Prop hub spun? My reverse is working as it should. Thanks.

 

[VE8EV]

Re: Omc electric shift slipping in forward gear

Easy enough to pull the prop and check to see if the shear pin is broken. If that's not it then its some sort of bad news in the lower gearcase. A bad electrical connection would be much more dramatic than "clicking".

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

I am pulling the boat tomorrow to take a look at it. If the drive pin was broken there would be no reverse either right?

 

[Boomyal]

Re: Omc electric shift slipping in forward gear

Not sure how a broken shear pin would react in reverse. What I do know is that you do not have an electrical continuity problem. If you did the forward clutch spring would snap the first time continuity was lost then restored.

 

[VE8EV]

Re: Omc electric shift slipping in forward gear

Some more info on what the problem might be here:
http://forums.iboats.com/mercruiser-i-o-inboard-engines-outdrives/omc-175-electric-shift-slipping-forward-gear-49774.html

I'm fortunate that the lower unit is one part of mine that I've never had a problem with (knock on wood!)

Good luck!

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

I pulled the boat today and it appeared I hit a good size log with the prop and there looked to become sort of twine wrapped around the prop several times. I pulled the prop and the drive pin is fully intact. And the drive shaft spins very smooth and free. I noticed maybe the rubber hub in the prop had spun because it looked like the prop sleeve had backed out of the prop about a half inch compared to my back up prop. I put the prop in a vice and tried turning the center sleeve with a long bar and it move slightly back and fourth but would not spin out of it's location. I drained a little oil out of the lower unit and it looked perfect as the day I put it in no metal shavings or water. Also putting it in forward and reverse felt strong and seemed to work as it should.I was thinking about just ordering a new prop from propco as I do not trust my back up prop. Should I start here or tear into the lower again?

 

[Boomyal]

Re: Omc electric shift slipping in forward gear

I do not think your propeller has a rubber hub. That is why it has a shear pin. It may, however be some kind of bushing that has the splines on it. I would at least try your backup prop to see if your problem still exists. What were the signs of having hit something? You did not mention any distortion of the prop blades.

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

It does have some kind of rubber hub in it I can feel it when I move the center sleeve back and fourth. It does not have a shear pin, according to the manual it is called a drive pin. The blades are pretty beat up. My marina pulled a good size log out in my slip with prop marks in it. I will give the other prop a try tomorrow see what happens.

 

[Howard Sterndrive]

Re: Omc electric shift slipping in forward gear

there are rubber hubs. propco still makes new stringer props for decent prices. they might be the only ones now.

 

[VE8EV]

Re: Omc electric shift slipping in forward gear

It does have some kind of rubber hub in it I can feel it when I move the center sleeve back and fourth. It does not have a shear pin, according to the manual it is called a drive pin. The blades are pretty beat up. My marina pulled a good size log out in my slip with prop marks in it. I will give the other prop a try tomorrow see what happens.

Drive pin = shear pin but you know, my boat came with three spare pins in 1975 and they're still taped together in the glove box. Hit something once with an aluminum prop and busted a blade right off but the pin didn't break. Another time we hit a deadhead log just under the surface at cruising speed. Engine stalled on impact and I found a four-inch thick branch jammed in the prop. Pried it out and carried on, no damage to the pin or anything else. Maybe drive pin is a better description...

Hope you find your problem when you try the other prop!

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

Got down to the boat today and checked to see if the ohms on the forward and the reverse coils were within the 4.5 to 6.5 ohms range and the forward coil was definitely not! It read 2.9 while my reverse coil read 6 ohms. If a coil is shot wouldnt it usally read no resistance 0.00? To me it would make sense that the forward coil is shot and that's why it's slipping. Wow are these vintage parts hard to find. I ended up finding a new one in town for $287 I figure I will give her a shot.

 

[Redrig]

Re: Omc electric shift slipping in forward gear

look around for a "new" lower unit, probably could find the whole unit for less than 287 and you have to tear into your lower unit , could just easily swap them out.

 

[bruceb58]

Re: Omc electric shift slipping in forward gear

You use type C oil in your lower unit?

 

[Howard Sterndrive]

Re: Omc electric shift slipping in forward gear

what happens in an electromagnet, is the polymer insulation on the wires begins to break down with age.
If the coil of wire has 1000 turns, and the insulation fails between say, turn 600 and 700, then 100 turns are bypassed by the current, therefore the resistance goes down by 10%
On yours, approx 50% of the turns are bypassed.

Now, OMC expected the insulation to break down, but not on adjacent (touching) turns of wire. If two insulation breaches happen, continuity may be made through the oil. So, OMC spec'd Type C oil, which does not conduct well.

Point being, an oil change with new, water free type C, may buy you some time.

 

[Howard Sterndrive]

Re: Omc electric shift slipping in forward gear

what Bruce said... lol

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

Thanks for the info. I do you type c oil and always have I think I'm just going to bite the bullet and get the new coil I'm going to tear into it tonight, I already have all the seals and new locknut for the vertical shaft so this should be quick and easy! I just wish I would have put a new coil in the first time when I put the spring in!

 

[Redrig]

Re: Omc electric shift slipping in forward gear

I may have one laying around from my parts spare. Dont drop 300 on one yet . Let me check it out tonight.

 

[Thane2012]

Re: Omc electric shift slipping in forward gear

I took the drive off the boat and put it on my stand. Before taking it all the way down I decided to check the ohms with it off the boat. I am really glad I did this as it showed 6.1 ohms on The rear coil and 5.8 on the front I was very excited at these results. Before I was reading the ohms through the boat with the wires still hooked up and the shifter in drive ( didn't realize this till later!) so I'm sure that's why my ohmmeter said what it did. I got my new prop from propco on thursday and put the boat in Friday and it runs perfect! Thanks for all the info!

 

[bruceb58]

Re: Omc electric shift slipping in forward gear

Great news!