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OMC slipping in gear

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webbcrafter

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"Help! 77 OMC electric shift s

"Help! 77 OMC electric shift slipping like a car auto tranny in forward and reverse.Works at idle,than slips when rpm increased.Passed "standing on prop" test,has proper voltage in forward,but not reverse.What now?"
 
"Mike, Sounds like an interna

"Mike, Sounds like an internal shift coil. Try a different prop and check all shift related wiring before proceeding, also change the oil. Be sure to use OMC Premium Blend lube. Unfortunatly it sounds like you're in for some surgery.

You may want to start watching e-bay, you can probably find a complete lower for less than the cost of this repair.

Good luck
Rick"
 
"Prop seems to be fine,still w

"Prop seems to be fine,still wondering why voltage correct in forward but not reverse,when it slips in both.If shift hubs damaged or springs broken,why can I turn the motor over when turning the prop?I was assuming mechanical damage,but hoping for other possibilities before tearing down."
 
"At what rpm in forward is it

"At what rpm in forward is it slipping? Are You sure it is not a leaking exhaust seal between drive and intermediate housing sending exhaust to the prop? And for reverse, is it just exhaust pulled into the prop? Do not think there is a mechanical (spring/coil failure in both forward and reverse. What may be is a cracked alu sleve and/or oil problem.Pos 11 in pic.
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"It starts slipping as soon as

"It starts slipping as soon as rpm increased from idle.When it first started slipping,speed slowly decreased from about 25 mph,now it won't reach over about 5 mph.I had suspected another driver had put it in reverse while still going forward,but can't confirm.
Will check seal and oil,thanks.
What would cause voltage loss?"
 
"Where are you checking the vo

"Where are you checking the voltage and are you sure that what you are seeing is not normal?

Oil viscosity is imperative in this system. I would put changing it at the top of my list. Also, verify what wires should have power and when. There were several versions of this system and they did not all work the same way. It's way too old (OK I'm way too old) to remember how it worked 30 years ago.

Good luck."
 
"There should be a constant 12

"There should be a constant 12 volts plus (according to boat mechanics I have talked to)at both forward and reverse shift wires(when engaged).I'm reading just under 13 consistently in forward through all rpm ranges,but only 5 to 6 in reverse.Still need to check oil and exhaust seal.
Appreciate the input,will update as soon as possible."
 
Even if someone put it in reve

Even if someone put it in reverse while going forward it wouldn't take out the forward spring. It will take out reverse real quick if this is what happened.
As far as the voltage not being the same the reverse coil could be bad.
Why you have slipping in forward is strange if the spring and coil are good.

It also been a long time for me as well since I last worked on this type of unit but I think an ohm test may tell the condition of the coils better than a voltage test.
Of course the coils need to be disconnected for this test.
If the ohm readings are close to the specs I'd look at the control switch and wire harness before taking the unit apart or try jumping the power to the coils and see if it helps.

To me it sounds like a power supply or coil problem. But I also think the prop is bad.

If I recall right when the spring breaks there is no engagment at all in these units.

Just for grins change the prop. The stand on the prop test doesn't always tell the true condition of a prop. I had a friend that had the whole drive rebuilt because it was doing the samething as you have. After $3000.00 later it was the prop. It is worth a try don't you think?

Good luck.
 
"Mike, 5 or 6 is no good. Do

"Mike, 5 or 6 is no good. Do yourself a favor, don't go by what "all the boat mechanics you know" tell you. This thing is a breed of its own. Invest in the service manual. If you are going to attempt to fix thing yourself it pays to have good information.

I've forgotten more than I remember about thsese things since they haven't been built in 29 years, but books don't forget.

5 to 6 volts tells me that either the coil is shorting or you have a wiring or switch issue.

Confirm the proper voltage, then proceed.

Rick"
 
"Are you getting these voltage

"Are you getting these voltages with the lower unit connected to the harness? The engine dosen't need to be running to perform these tests. Disconnect the shift wires before the intermediate housing at the knife connections.(make a note of the colors, or mark them)Between a good ground and each harness wire you should get 12v with the ignition in the run position. Don't leave it this way too long or you can burn your points. Ring out the coils to ground. They should fall between 4.5 and 6.5 ohms. Mine ring at 5.7 . Getting 5or6 volts with the coils hooked up means that you are pulling alot of current through that coil. The coil could be partially shorted, or the shift cable might be compromised somewhere in the lower unit. Good luck!"
 
"Forgot to mention, when this

"Forgot to mention, when this problem happened to me, it ended up being the pump shaft in the upper unit being stripped out in the upper bearing carrier shaft. Check the condition of the oil in the upper unit. Mine was alfredo sauce."
 
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