1972 OMC 155 Stringer-No reverse

[hunt2labs]

Great forum-thanks for all the helpful posts I've read about this issue. I have downloaded the repair manual someone was very kind to put out there.

1972 Steury V518, 155hp OMC. Electric shift.

New boat to me. Put on water first time last year, reverse worked but motor would kill each time it was engaged.
Idles well in forward, runs great flat out.

After a long winter we do not have reverse at all. Engine revs when put into reverse.
Prop does spin forward when in neutral but is not engaged fully.
Prop continues to spin forward when put into reverse.

Not sure if fluid is OMC or not.
I am going to replace first thing today.

Question: Having had no luck finding a mechanic around Madison, Wisconsin who will work on this system, how much time, effort, labor might it take to get at the magnet, spring area?

I have 12 volts out of each solenoid but have not gotten to the leads at the outdrive to check yet.

If I have same issue with OMC Type "C" fluid, please advise next step.

I can locate another outdrive for around $400 not too far away.

Would you put on a "new" used outdrive and keep fingers crossed or go at the repair figuring it may be the spring or magnet?

This is coming from someone with limited $$ and a wife who is not so happy with this thing sitting in the driveway blocking the garage.

Thank you!

 

[Redrig]

Re: 1972 OMC 155 Stringer-No reverse

First make sure there is type C in the lower.

next, down by the tilt motor in the bilge area , you will have 2 wires going into the outdrive through the intermediate, blue and green make sure you are getting 12 volts to the blue wire for reverse when shifting. If you are not getting 12 volts the problem is in your controller, there are no sileniods for the shift, just cranking and the tilt.

if it is your magnet or shift spring, it is not terribly difficult. The reverse mechanism is at the back of the lower so it is better to lose reverse than forward in that regard.

check the OHM's on that reverse magnet as well before you tear into it.

either way, it shouldnt be more than a couple of hundred bucks to fix , assuming you do it yourself.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

Got Type C oil heading out to run it with water running through system.
Thanks for the info. I mis-stated the solenoid deal...there is power to each wire by the tilt motor.
Fingers crossed.

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

unplugged, either wire to the lower unit should have 4 to 7 ohms compared to battery negative or good ground.

The killing the engine thing makes it sound more probably a mechanical issue inside the lower.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

Well. New fluid seemed to help get it in gear, but now it stalls shifting into either gear.

Also after draining and adding proper fluid type to lower unit, I noticed teardrop-sized droplets coming out of what appears to be a pinhole in the outer housing located where the front (bow facing) lower unit meets the first cavitation plate.
Guessing that I have more issues than hoped?

 

[southkogs]

Re: 1972 OMC 155 Stringer-No reverse

What kinda' shape is your upper gear case in? (Just to eliminate that possibility) It might help to remove the stern drive to see if the engine bogs out and dies on power up or not. That would confirm Howard's suggestion that it's drive related.

I can't picture exactly what you're explaining at the cavitation plate (photo might help), but it doesn't sound right.

If that other outdrive is in good working order at $400, that's a pretty good price to get ya' a spare.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

We ran it flat out the other day going about 32mph and everything sounded fine then-except for it not going into reverse and racing the engine.

I cleaned the carb and hope that will help.
First things first.
The photo attached shows the pinhole just below the arrow I drew. Hard to see since it's so small.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

After testing for Ohms, I am pretty sure I have a bad coil or broken wire.
Both green and blue leads were all over the place on the meter-never settling on any one number.

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

After testing for Ohms, I am pretty sure I have a bad coil or broken wire.
Both green and blue leads were all over the place on the meter-never settling on any one number.

were you pressing your fingers on the probes?

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

After your idea, I checked with 'gator clips and no matter what setting on the meter (2000K - 2000) I got readings all over. @ 2000k it settled at zero, danced all over with other settings.

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

numbers shouldn't be changing no matter what the issue
you want to leave it on 20 ohms scale (or whatever the lowest scale is) - turn off autoranging
and take the measurement


then, touch the two meter leads together and if meter reads anything but 0 ohms, the meter is not reliable

hope that helps

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

Older digital meter does not have option to turn off auto range.
However, I did not get zero on testing meter leads together.
I'll have to hit the hardware store tomorrow.
Thanks again for all the help!

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

Finally got back at the leads with a new analog meter.
Reads zero on both wires were the breakapart is located by the trim motor.
Still not having much luck locating mechanic up this way.
Forward engages just fine.
Reverse has no action on the prop shaft.
Prop does slowly rotate forward while in neutral and reverse- it is not not engaged as I can stop the spin with a gloved hand.
I cannot find anything in the online repair manual that addresses this.
Can I simply pull the lower unit apart or am I asking for a heap of trouble?
Do I need to pull the whole outdrive and follow the repair manual steps and work down to the magnets and check the springs and or voltage to coils?

Thanks again!

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

Reads zero on both wires were the breakapart is located by the trim motor.

Forward engages just fine.

still a problem with the meter or the way you are using it, because those 2 conditions can't exist together.

don't disassemble anything until you are 100% what you are looking for.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

still a problem with the meter or the way you are using it, because those 2 conditions can't exist together.

don't disassemble anything until you are 100% what you are looking for.

Hmmm..
The meter I picked up has Rx100, Rx10, Rx1...
I put the negative on the engine block and positive probe on one of the wires using an alligator clip for good contact.
The meter stays at zero. I know the meter works on DC volts and AC.....guess I need to find a little help on this end.
I'll try again tomorrow.
Thanks

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

RX1 is the only scale you want to use
sounds like you're testing it correctly, but if there is really 0 ohms, that's basically a dead short, which would immediately blow your ignition fuse when you put it in gear. weird.

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

I'll check again when the rain lets up-I may need that boat if it keeps raining....
just to clarify...I've taken the wires apart at the quick disconnect and am checking resistance from that point down to the lower unit?
Or should I be checking the continuity with the wires connected back to the shifter?

 

[Howard Sterndrive]

Re: 1972 OMC 155 Stringer-No reverse

You are correct to undo them.

Red lead of ohmmeter on terminal of FWD light green wire heading into sterndrive, black lead to battery negative or good ground.
should read 4 to 7 ohms

Red lead of ohmmeter on terminal of REV light blue wire heading into sterndrive, black lead to battery negative or good ground.
should read 4 to 7 ohms

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

Well, found out the reverse wire was totally broken at the coil face-no fixing that. Plus the spring is broken. Looks like I may be able to find both on Craigslist not too far away.
Everything else looks solid in the lower unit-small amounts of shavings on the magnets. Gears look good....
I have not pulled the forward coil to check what is up with that. I had forward and neutral working fine-even with the strange ohm readings (zero) on both coils. Not sure why, but testing the reverse coil while out of the unit, grounding to itself, reads zero on 3 different ohm meters.
I even had a marine mechanic test both leads wires to coils prior to disassembling the lower.

Now that this puppy is awaiting replacement or repair, dare I delve into the impeller??
That seems to require a bit more skill or tools than I may have.

Everything else seems solid, well lubed, little wear on drive, no water in lower unit.
Coho salmon are getting closer by the day....

 

[hunt2labs]

Re: 1972 OMC 155 Stringer-No reverse

I wonder if the reverse wire was grounding out the system where it broke off at the coil. Still it read zero after I had it out.
Hmmmm????