Logo

75 Omc electric shift stringer disengages for a moment under load (190 hp 5.0 lt FORD)

Rob Howells

New member
Hello everyone,
I am at a loss on the next action to take with this problem. I will begin with some basics -- it is a 1975 23' Fiberform with a 800 stringer electric shift. Its a great design for family boating now that we have replaced the stringers once and the floor twice not to mention just about every piece of hardware on it including paint inside and out (also have rebuilt it's unruly trailer). Moral of the story is I'm in too deep not to fix this problem i've been trying to diagnose for a couple of seasons. (we inherited it for free bout 7 years ago - ha, not free anylonger $$$$).

So, the problem:

This boat purrs like a kitten until it's about half way up on it's plane, under heavy load bout 3200 rpm's and then it let's go violently (almost like neutral) only for a moment as I pull the throttle back, then it rengages. It does seem like you can avoid this by feathering the throttle up super slowly, avoiding any large waves, and easing it onto a plane. It has also been know to happen while cruising at a good clip on flat water (higher up in the RPM range 3000 - 3500).

Now the crazy part:

After reading lots of forums and racking my brain on which part of the boat to tear into further - we have had the prop rehubbed twice (with a garantee that the second one did not slip, but we rehubbed it anyways). I then figured it had to be the forward coil solinoid or spring in the lower unit. The lower unit was then packed up and shipped to Canada (you know the place!) to be rebuilt. $700 later, they called me explaining that there did not appear to be any problems in the L. unit but the rebuild and resealing was complete. They thought the problem was in the electric throttle shift switch which they supplied me with a replacement. Unfortunately my updatd throttle does not seem to except this switch. I still am finding it difficult to believe that it is an electric switching issue as that it seems to be so related to the drive being under load.

Any Ideas ??

Any ideas on testing the current switch i am using or if the problem may lie deeper in the outdrive or intermediate housing - the only 2 parts left I haven't torn into yet. My fear is the shimming, rolling tolerances and proper gear mesh spec comments in the service manual, not to say any unneeded expense if i make another wrong diagnosis (i mean guess) of what the problem really is.

Pretty sure the prop hub is good
Pretty sure the lower unit is good
Pretty sure the shift switch on the throttle is ok, old but ok.
(super simple 1975 mechanical designed switch which you can visually see the electrical contact being made).

This seems to be a challenge in diagnosing exactly what is slipping. It's killing me. Thanks for any help or ideas. I am hoping someone has experienced this already and can save me some cash. We even named her FREEBIE bout $6500 ago.
It is nice and we do love it we just want it to work !

Oh well, B.O.A.T. = Break Off Another Thousand --right?

Captbert (New User of MarineEngines.com forums)
 
Ok if you didn't know i will try to explain.

Power goes to the drive thru the flywheel that has a COUPLER that has splines that has a driveshaft the goes thru the transom to ball gears that goes thru to the drive thru 2 other shafts to more gears to the prop.

There are also as you know unique to this drive a forward and reverse " spring "

So ether the coupler is going which maybe. But i don't think so. You coupler ether goes or is good, once it goes you don't go anywhere believe me i know had it happen to me. It's a one piece no rubber. The splines go your stuck in the water.

So whats left ?

The 2 shafts in the upper. They go your stuck. Happened to me right after the coupler went on the very next trip out.

I don't think that's your problem ether.

So the guy in Canada thinks your switch is not letting current thru sometimes and other times it is. Not what i think your problem is.

I think it's the spring, It lets go and then when you slow down it grabs again.

Gears if they go you will hear it and see tons of metal in the gear oil if you look.

I bet you drained the drives and looked if not you should.

You ball gears are good ? You running the drive always fully down?

Ok before you do anything try this.

You and a friend grab the drive while fully down and try to raise it. No power button nothing just brute strength. Grab it by the lower and try to raise it.

There is a method to my madness, and you will have to have faith in a guy on the net you know nothing off and you think is totally off the wall.

Post back i will be waiting for your reply.
 
Last edited:
Thanks Chief,
For the speedy response. I am actually reinstalling the lower this week after it's nordic adventure to Canada, eh'. I am more than willing to find out where you are going with this brute method. Im excited to see what happens and hear what you think. I also wanted to mention that back in 2009 we lost the the water pump shaft and the vertical drive shaft right above it. We did replace both the waterpump shaft and the one above it that it fits into. The ball gears do have some wear but they seem like they are functioning. I went ahead and changed out the water pump, while I was in there, and and the splines on the water pump shaft looked good.

I should button it back up by this weekend and I'll let you know how the brute strength test goes.

Thanks again for any and all advice. I will be back soon

Having faith !
Rob
 
The forward clutch spring is slipping on the hub in the lower unit.---------Common problem and an easy fix for me.----------------Most shops will tell you it needs a new forward spring and a new drive hub ( big $$$ ) but there is a much easier fix that shops with 30 + years do not know about.--------If you keep running it you will eventually break the tab off the forward spring and have to come home in reverse.
 
my first thought is to try another prop - I know, it's been re-hubbed, but I always try easy stuff first, and maybe there's some issue with the way it's grabbing the pin, or the press bore for the hub. Did they use the right hub? - didja know the pre 1968 hubs are slightly tapered? and post 68 are straight...

the w/p shaft splines can slip and re-weld or catch-but not forever... probably a half dozen times... dunno... engine coupler too

TC has rebuilt hundreds of electric shift lowers... they could still be wrong.... hard to say
B.O.A.T. = Been Over At Toronto
 
OK Chief, we installed the lower, and did the brute strength test on the tilt clutch and found a small amount of movement maybe 1/8 of an inch or less play and then stops solid. We could not get it to move up by brute force alone and the play seems to be only in the teeth of the tilt motor gear or possibly where the splines of the tilt gear meet the clutch shaft ???. The tilt motor does seem to bind at times where you need to help it a bit or change tilt direction to get it moving again. What do you guys think?

Thanks again for all the responses
Capt Bert
 
You have 2 problems. Below is the fix for the tilt.

How to fix stringer tilt problems!

So you have a stringer out drive that won't tilt up, or it tilts up very slowly, or you need to help it up physically. Maybe it doesn't move at all.

Here is a step bye step guide to fixing it. A manual would be very helpful.

1- A fully charged battery is imperative.

2- Disconnect the battery and clean the battery posts. Are the cables good?

3- With the battery disconnected, clean all the connections on the port side, solenoids. Don't forget the grounds.

4- Clean connections to tilt motor. Two wires.

5- Connect the battery.

6- On the out drive port side, there is a clutch housing. Four screws hold on
cover. Pull that cover. May be full of water. They all leak.

Two things you can do at this time.

A- Clean out the housing with clutch installed.

B- Remove the clutch and rebuild the housing. New seals.

If you chose A, Spray the clutch with brake cleaner. Make sure it's as clean as you can get it. You might have to spray it a few times. Blow it dry. Spray the the clutch with penetrating oil. Pack the housing with grease, and install cover. Don't over tighten the screws, can bind the clutch.

If you chose B, remove all the components of the gear housing. Soak everything in Acetone overnight. Rebuild housing, new seals. Blow dry the parts, soak them all in motor oil for a hour or two. Install parts. Pack the housing with grease. I know it calls for 30 weight motor oil. Trust me pack it with grease. Install cover.

7- Gently pry off the rubber bumpers. Don't mix them up, pump grease in the zerks. Install bumpers.

At this point the drive should move up and down easy. If it doesn't, you need to pull the tilt motor. Test motor and replace or rebuild. Make sure the hammer blow coupler is good or replace. Don't forget the gasket, on the tilt motor. .

Good luck!​
Now to the problem of the slipping at high rpm.

The coupler you have that is attached to the flywheel is a one piece on your boat when the splines go you have no movement of the boat so i don't think that's your problem.

Next the spline of the shafts in the drive when they go you have no movement of the boat, i don;t think that's your problem.

So what i do think is your problem is the spring in the lower drive.

You already addressed the prop.

Then again someone else might have a idea.

If this was a latter model stringer then i would say maybe the clutch dog but this isn't.
 
No switch springs.------------------I demonstrated my technique to a dealer with 30 years experience once and he said----" in my wildest dreams I would not have figured this out "--------Bought the tool on the spot.-----------------My expertise has been " scoffed " at ( in MY opinion ) by internet folks and am certainly not going to share " for free "-----------------SORRY.
 
I can tell you any drop in voltage to the elec. clutches is like your hand grip on a pipe !(low voltage) is like a loose grip, the pipe will spin. Try a independant 10 gauge wire direct to positive battery and clean your grounds or run a separate wire also, both direct to the shifter throttle switch,just to try, or you can also clip a multi meter to existing terminals on the switch test run and notice any voltage change. test at the conections at the rear harness too.
 
I am having the same exact problem on my 1977 302 omc 175 hp. I am still in the early stages of trouble shooting, but your forum has been helpful. Please continue to post your progress and/or resolution.
 
No switch springs.------------------I demonstrated my technique to a dealer with 30 years experience once and he said----" in my wildest dreams I would not have figured this out "--------Bought the tool on the spot.-----------------My expertise has been " scoffed " at ( in MY opinion ) by internet folks and am certainly not going to share " for free "-----------------SORRY.
:)
see ya on dragon's den.. haha
 
Well i'm back and seems with a boat that only goes in reverse. I need to note that the Colorado River has now tried to swallow her up for the third time. Once was early on before the restoration on Lake powell (freak summer storm cell out of nowhere) with some monster waves. The second was on a surprize storm one afternoon on Lake Mead with a dead battery (The irony here was it was in a freak "electrical" storm). And now the latest was at Lake Havasu when the outdrive forward gear gave out leaving us in the path of another freak desert isolated storm cell with only the reverse gear. I do wonder exactly what a "freak desert isolated storm cell" actually is defined as a have been trapped in serveral.
 
Yea we slapped the outdrive on and gambled on it to a trip to Lake Havasu AZ. I thought I would share the story as my belief is these stories are why we go on these adventures of boating. or at least thats what I'm telling myself. My wife says I'm to wordy but I like to set the stage.

So read on if you want to hear bout it:

We headed for a full seven day sun filled boating trip to the world famous London bridge at Lake Havasu Arizona with our Canadain repaired OMC classic. We arrived in the weather that we were searching for, bout 118 F day time and would almost cool down to 103 at night. (I know, way hot but we live where it snows.) Lake temps were around 80 something. You wanted (needed) to be wet. We dropped the Fiberform in and begain motoring. I took it easy getting her up on a plane that first day and eventually had her running smooth at some good RPM's, right around the 4500 range (max) at times. I even gave her some pretty hard accelerations where it performed flawlessly. I figured, somehow by rebuilding the electric shift lower end, that they had exercised my little demon of a lower end problem. Days went by without issue growing my confidence allowing us to venture out a little bit further each time we went out. We pulled wakeboarders put on some miles and had a real enjoyable time. We were having such a good time that towards the end of the week we invited some friends up to meet us for a couple of days of boating and sun and fun. Our friends thought this boating is real cool and they could get into it.

And then things turned a bit in the last few hours of the last day. We were heading in to the ramp when we realized that our friends had not expierenced the amazing London Bridge, (which come on, its a bridge - not even american) but was there to be expierenced. It is important to note that it does require about a 25 minute slow parade speed cruise (no wake) with lot's of other boats (and there exhausts) in some big time heat to actually drive under the bridge, which at the time, sounded quite fun to all of us. After the "expierence" we proceeded out of the channel at sundown, spectacular, especially with the desert storm cloud in the distance sillouetted by the sunset. Truly beautiful and a great finish to the trip. Until.....I really hit the throttle to fight back some of the headwind in which were driving against. Due to the activities my crew had enjoyed earlier in the day they had all moved towards the back of the boat which was also not allowing me to get her planed out, so a bit more RPM's. Then it happened, out drive gives out. Done, She did pop right into reverse which we decided to try and reverse back into the channel. I knew the dead boat and the approaching storm were not a good combination as explained earlier I had done this before at Lake Mead. Our friends seemed a bit uneasy but I as the Capt. showed no fear acting like things were under control and we would be home soon enjoying an after boating cocktail. By now the wind from that one lonely little storm cell in the distance had picked up considerably as well as the storm itself had encroached. I do have to share that a boat in reverse has an extremely hard time navagating anywhere in heavy wind. Our friend stated "that there must be a protical that should be taken in the event something like this was to happen" which at that time i almost broke out my oar for her, but in order to avoid panic and ruin the adventure she so far seemed to be enjoying even with the wind and looming dark cloud (singular), my paddle stayed stowed. At this time I did hand her my "person in water"orange flag and told her that she must wave it vigorously and constantly to make her feel as she truly had a part in our safety. (I told her this was the protical as we were stuck only going backwards). Other boaters were looking at her wondering why in the world we would have anyone in the water with this storm upon us. Eventually and backwards we did manage to get it to beach in a camp ground with some very helpful campers. They must have been boat owners as well as they all ran down beach hitting the water like life gaurds in an episode of bay watch to help save my boat from the giant swells that have now grown to try and eat my boat. Probablly 10 people showed up in the dark to help me load my craft to her trailer in this storm, in the water, among the airborn sand and at a non-designated boat launch. It was awsome and our friends went home saying the felt bad for my boat but what an adventure to remember. She did take on some water which made here quite heavy and caused some difficulty to get her on the trailer but the moral of the story is that she is now home, broke for the time being, but home and dry (and so is my boat :humor:)

Well now what to do next...Hmmm...

Thanks for listening

CaptBert
 
I own a 1975 electric shift stringer and started jumping out of foreward gear at low speeds. happened 3 or 4 times and now no foreward gear. Did the ohm and amp tests and all was within specs. Started removing drive and dis-assembling drive to get to lower coil and shift asembly. One big problem with dis-assembly. Cannot pull electric shift wire through the holes. It cannot get past the molded ribs in the wire. Used plenty of lube and now I'm thinking of heating wire up with hair drier to soften the rubber so it will pass through the hole in the exhaust housing. I have already damaged the rubber sleeve on the wire but I don't think i shorted the wiring. Hoping to get past this hurdle so I can continue with dis-assembly and hopefully locate the shift problem.

any hints or comments will be appreciated. Thanks, Chuck E.
 
Hello Chuck , I'm thinking the passage has corrosion and has narrowed , Does the wire move inward to engine side ? if the wire will go toward engine 2-3 inches or so try this. take a piece of 80 grit 3''x6'', roll it around a pencil the long way,then wrap it around the wire tightly like rolling a smoke ! then see-saw it back and forth through the hole, not too much just enough to get the wires rubber ribs through, and adding some heat and grease will benifit, the wire is 125.00 so be gentle. IF the wire is stuck and doesn't move either way i still know corrosion is the culprit ,Now from inside hold the wire up and pour CLR (rust & scale remover) down the wire, take some mig wire or mechanic wire and start poking all the way around the rubber wire(gently) it just gets the CLR deeper, keep doing it for a while to see if you are getting any where, or leave it overnight with a CLR soaked paper towel on each side , try this : if not you can try some muratic acic but that will require some extra CAUTION !! GLOVES ,GLASSES,CATCH RAGS OR DISH, ECT.!!!!!!! TRY CLR FIRST, AND LET ME KNOW BEFORE YOU TRY THE ACID. Good luck. David.
 
12splash,

Thanks for the rapid reply. I like the CLR idea and emery cloth. I wont be at the garage until sunday. I will let you know as soon as I get results. I would be worried about using myriatic acid until the wires are completely out and at that point the emery cloth will do the job. I assume that the rubber is hard from age and the heat will help. I will soon find out. Thanks again,

Chuck E.
 
Back
Top