Omc outdrive knocking noise while cruising.

[dac018]

Hello,
I have a 1988 Bayliner Trophy with a 350 SBC 5.7L, along with the traditional OMC outdrive. It was a project boat, old engine was seized and ended up putting in a new engine. Previous owner removed the OMC 5.0 and put in the 5.7(the one that was siezed). I just got a remanufactured 5.7 that worked. I've taken it out 9-10 times now, nothing major happened just working out the kinks and testing propellar sizes. I was very impressed how well everything was going, considering without youtube it would still be in my driveway, untill this last prop change. This last time I went from a 15x19pk(wot 3700, mph 38-39) to a 15x17p( wot 4100 mph 37). I'm still testing props, were getting closer to wot 4600. This last time everything was good, maybe 4 hrs in I heard a clunk or knock, like I hit something, I looked back but didn't see anything I could have hit. It did that 2 more times during the trip. From reading what it could be and how it felt, I think the lower units gears might be slipping or something down there is failing. Does anyone have any thoughts? I replace the upper and lower shift cables with the OMC tools. It's shifting smoothly finally so I dont think thats the issue but I really have no clue. I've been looking at a replacement lower unit, either rebuilt or the new SE109. Ive also explored the mercury and volvo conversions, the last thread about this topic i found was in 2011 and just seeing if anyone has had any new ideas or new info about the SE units? I've already put alot into the boat so im not gonna go the cheapest route if its a crap choice but also realize its a 36 year old boat and need to draw the line somewhere. Im just tryna see if I need to jump on it right now or ride till the wheels fall off. Thanks guy thats the outdrive and tag on it.

 

[Redrig]

Probably your dog clutches , if you Google pics of those , they eventually will round and that clunk you are feeling is when they slip to the next tooth.

Not a terribly hard job , just getting the right tools and parts may be the real problem though, as you mention.

I "believe" on certain years there was a recall , and they were replaced with dog gears that were undercut to address this problem . So if you decide to try and replace them , see if you can locate the updated ones.

I have a stringer so take that info for what it's worth , thats just from reading these forums, I don't have any first hand experience with it.

 

[kenny nunez]

I replaced the gear set under warranty several times with the under cut gears which cured the problem.
Without the shimming tools replacing the gear set is a dice roll. Also the threaded shift rod has to be exactly the same height. Before you do anything with the lower removed screw the “chicken lips” in counting the turns until it bottoms out and record that.
Does your inner transom plate have the shift interrupter electronic module system? If not a lot of that stuff may now be NLA.
If it does have the system and you are not using breaker points in the distributor then the system will not function correctly. And you will not be able to shift out of gear easily if at all with the under cut gear set.
If you really want to get it right I would pursue a drive set up using a drive with upper cone clutch shifting and a belt drive raw water pump drawing water through the bottom of the boat and you will be through with future problems.

 

[Lou C]

I recall reading about the recall on the Cobra lower gears, what they also found was that a supplier changed the spec on the lower shift cable, they had too much drag and were causing the drive to not shift fully into gear and that rounded off the clutch dogs/lower gears. The new cables were red not black and had proper drag (2.5 lbs or less measured with a fish scale).

The first thing to do when setting up a Cobra shift system is to disconnect both ends of the cable and measure the drag in both directions. I have done this, followed all the other steps and it still shifts perfect, 12 years after I did the last set up.
The other thing that helps is to pull the drive each season, and clean out the recess behind the shifter bell crank in the pivot housing. If the gasket between the drive & pivot housing leaks, water deposits will cause that area to get crudded up and restrict the movement of the shifter bell crank.
Lastly to ensure good shifting your ESA system must work, idle speed should not be more than 600 rpm on the water and when you trigger the shift interrupt lever it should lower the idle speed to 450 or so rpm. If the ESA doesn't work, your shift to neutral will be very difficult and probably stretch the shift cable. And if your idle is too high the ESA may not be able to lower it enough.
If you need ESA modules and the micro switches you can still get them from CDI electronics and they also sell ones that will work with electronic ignition distributors. I still have the points but am considering changing it to the Delco EST IF I can get it to work right with the OMC ESA. I know there is a way to make it work by wiring it like a Merc Alpha but I'd prefer to keep the OMC ESA functional because it doesn't stall the engine during shifting if you shift a bit too slow, it is more complex due to the module but when everything is set up right it works very well.

The other option if you don't want to try to keep the Cobra going is to do the SEI conversion, this replaces your pivot housing and allows you to install a Merc Alpha on their custom pivot housing. You can use the SEI Drive or I would think even a genuine Merc if you don't think the SEI is made well enough. But it is a cheaper way to keep an old OMC powered boat going.
The other option is to convert it to a Volvo SX, this is a similar project you have to change the pivot housing to the Volvo one and add the engine mounted impeller, but a lot more costly due to the cost of the Volvo SX drive.

 

[dac018]

Thanks for replying guys! I rebuild pumps, gearboxes and other rotating equipment for my day job. Im familiar with shimming, its concept, and how to measure tooth engagement. Rebuilding the lower unit is my go to, I just need to tear it apart first and see if I can spot chipped teeth or some sign of where the noise is coming from. Im hoping a thrust bearing or washer is worn and causing too much play and I haven't destroyed anything. A guy can dream cant he? I found the lower rebuild kit with everything from T.C. Electronics for $1000 or you can get the SE109 for $1200. Just for Lazy reasons id spend the extra $200 if they are worth it, they do have a 3 year warranty as well. Although rebuilding the lower unit does sound fun to me. Also the mating surface when I remove the oudrive has damage just natural wear, ill post a pic. Ive watched a few videos and I'm fairly certian i can do that, I just dont want to fix a problem that going to come back, I like Kenny idea of getting rid of future problems

So the ESA system is there ive done tests and it doesn't work at all, no engine hesitation when I manually engage it either way and i cant get the multimeter to show continuity. The distributor was switched to a Petronix HEI maybe 6 years ago last owner told me. The ESA module was not updated for the HEI dist. Ive been looking to buy the right module for my set up but choosing which one is 'the right one' is beyond my skill set. I have an idea but not 100%.

To the shifting cable, it had a cheap Amazon $40 shift cable, it didn't shift right. I put in the correct sierra red cable, it shifts awesome now. The Amazon cable was almost an inch shorter. My idol is set around 600-650, lower than that the engine shuts off sometimes. Knowing the esa doesn't work is always on my mind though. I spent a day fine tuning the shift bracket, starting with the omc tools then adjusting to where it felt the smoothest possible. I dont have problems going in to forward or reverse and it does not pop out of gear when driving. I just have to commit when going into gear and it works well, im fairly new to boating. But maybe it is bad and I just dont know because I haven't felt a 'good one'.

Do yall have an idea on what the volvo conversions or the Merc would cost, of course its my labor so just the parts. Ive seen just the lower volvo outdrive is almost $4000. Yikes!

 

[dac018]

Don't worry I cleaned all that salt/calcium build up out, thats when I first got it. Just reminiscing. But you can see that outer edge there is barely any surface making contact with the gasket, it is just the one spot im concerned with but is a concern.

 

[kenny nunez]

I do not think there is a Petronics that will interface with your current ignition.
I myself have often thought how to add the Mercruiser shift interrupt to the OMC shift setup. That would eliminate the OMC system which I have never cared for.
Your problem is definitely shift dog related. I have been told that it is possible to have your gear set re machined to provide the negative angle with a new or re machined dog. You only need it done to the forward gear surfaces.
The earlier 800 stringers had hydro shift which used a pump in the front of the gearcase. I cannot remember ever having a dog slipping on those models.
If you do not have a Genuine OMC manual they can be obtained a Crowley Marine. They have some OMC parts that no one else may have.
Now you know what “chicken lips” are. OMC Technicians gave it that name.
There is a marine salvage yard here in the New Orleans area. They chain saw the transoms to salvage the drive systems.

 

[dac018]

I do not think there is a Petronics that will interface with your current ignition.
I myself have often thought how to add the Mercruiser shift interrupt to the OMC shift setup. That would eliminate the OMC system which I have never cared for.
Your problem is definitely shift dog related. I have been told that it is possible to have your gear set re machined to provide the negative angle with a new or re machined dog. You only need it done to the forward gear surfaces.
The earlier 800 stringers had hydro shift which used a pump in the front of the gearcase. I cannot remember ever having a dog slipping on those models.
If you do not have a Genuine OMC manual they can be obtained a Crowley Marine. They have some OMC parts that no one else may have.
Now you know what “chicken lips” are. OMC Technicians gave it that name.
There is a marine salvage yard here in the New Orleans area. They chain saw the transoms to salvage the drive systems.

So assuming my boat is on its 2nd possibly 3rd motor but outdrive has never been worked on, is it possible if I just replace the dog, the gears and all that stuff I could get another 30 years out of the outdrive? Or because the ESA doesn't work it will cause the gears to prematurely fail again? And also your saying with out a functioning ESA to not get the undercut gear set right? I have found a few esa modules on CDI that claim to work with my HEI distributor, like Lou said. My module is deffinetaly ment for a points system, but its so old I dont think it would work even if I had them.
I'm from TX but live in CA now, Louisiana is quite a trip for me.

 

[kenny nunez]

In the Sierra catalog where OMC ignitions and distributors are listed the Petronics system states that it is not compatable with electronic shift assist.
you would have to get a Mallory or a Petronics breaker point distributor. If it comes to that for your boat I prefer the Mallory point distributor.
there should be some boat salvage yards in your area.

 

[dac018]

In the Sierra catalog where OMC ignitions and distributors are listed the Petronics system states that it is not compatable with electronic shift assist.
you would have to get a Mallory or a Petronics breaker point distributor. If it comes to that for your boat I prefer the Mallory point distributor.
there should be some boat salvage yards in your area.

So 100%, im sure every one on this forum has more knowledge about this stuff than I do. Im learning all this for the first time. Im just looking things up on the web and I saw a 'fix'. It seems sketchy, but apparently its in the petronix box when you get it. Have you ever heard of this?
My distributor is the Mallory marine one originally with points, some one changed it out to the petronix hei at some point, I might go back to points if it will help extend the life of the outdrive.

 

[kenny nunez]

This looks like it would work. I closed my shop in 03 so while I still work on some old customer’s boats this fix was not available back then.

 

[Lou C]

So assuming my boat is on its 2nd possibly 3rd motor but outdrive has never been worked on, is it possible if I just replace the dog, the gears and all that stuff I could get another 30 years out of the outdrive? Or because the ESA doesn't work it will cause the gears to prematurely fail again? And also your saying with out a functioning ESA to not get the undercut gear set right? I have found a few esa modules on CDI that claim to work with my HEI distributor, like Lou said. My module is deffinetaly ment for a points system, but its so old I dont think it would work even if I had them.
I'm from TX but live in CA now, Louisiana is quite a trip for me.

Mine was redone before I bought it (probably 25 years ago) and it still shifts fine now. But when I got it the shift cable was sticking due to the build up behind the bell crank. I took it to a good OMC trained mechanic (2004) & after that it was fine. I learned how to maintain it myself & pulled the drive at the end of each season, cleaned out the recess in the pivot housing & made sure the shift cable was moving freely. I had to re-adjust it once in 2013, and again since then it’s been fine. The only other thing I had to do was replace the ESA module & micro switches about 10 years ago. Other than that just maintenance. The last repairs I did were the steering actuator (2021) and trim rams (2024). If your ESA doesn’t work you won’t be able to shift to neutral and the shift cable may stretch making it impossible to adjust it right.
If you for sure want an electronic distributor I’d call the tech support at CDI & see if they feel that the units they sell will work with the distributor you can get. Otherwise if you have a points distributor in good shape just replace the points & condenser!