OMC Stern Drive Hard Shifting Issue-gctid379291

[Guest]

This one is driving me crazy. Let me start out by stating that the lower unit is a 1988 Cobra and the innards (gears, bearings,ect) have been inspected and everything looks great. The shifter and throttle cables are about 4 years old with maybe a seasonÔÇÖs total usage on them and operate smoothly when disconnected. The interrupt switch appears to be working. Engine idle is right at 650 RPMs and is running smooth. And all adjustments of the cables at the carb are correct according to the Sealoc manual that I have.

Now on to the problem. When running on the trailer, and shifting from forward to reverse and back through neutral to forward it shifts like it should, no real effort is required and the shifts are smooth. BUT itÔÇÖs another story altogether when the boat is in the water; especially if the boat is moving at all. It is very difficult to get the boat out of gear, but fairly east to get into gear. When docking (I have to dock stern in) sometimes the shift lever has to be moved all the way to the forward position to get the drive out of reverse; during this process quite a bit of force is required. Needless to say about half the time it goes into forward requiring a quick shift back into reverse or neutral. Also when creeping toward a dock it can be very difficult to shift out of forward into neutral to keep the speed down (boating rule #3: never approach a dock faster than you are willing to hit it). At my dock, with the speed of the current when the tide is running this can be a very aggravating issue, plus itÔÇÖs playing heck on my rub-rails from bouncing off the pilings.

I have checked and rechecked everything that I can think of at least three times and canÔÇÖt find anything out of adjustment or anything that looks worn. As much as I hate to, I might have to turn this one over to a marina that has a few techs who know their way around the OMC stern drive.

Is there anything that I may have overlooked?

[2850Bounty]

Wingnutt wrote:
This one is driving me crazy. Let me start out by stating that the lower unit is a 1988 Cobra and the innards (gears, bearings,ect) have been inspected and everything looks great. The shifter and throttle cables are about 4 years old with maybe a seasonÔÇÖs total usage on them and operate smoothly when disconnected. The interrupt switch is working and as far as I can tell is adjusted correctly as it hits the top of the ÔÇ£camÔÇØ right as the shifter cable starts to engage the gears. Engine idle is right at 650 RPMs and is running smooth. And all adjustments of the cables at the carb are correct according to the Sealoc manual that I have.

Now on to the problem. When running on the trailer, and shifting from forward to reverse and back through neutral to forward it shifts like it should, no real effort is required and the shifts are smooth. BUT itÔÇÖs another story altogether when the boat is in the water; especially if the boat is moving at all. It is very difficult to get the boat out of gear, but fairly east to get into gear.

That's an inherant issue with Dog Clutch style gear engagement.... or I should say, gear disengagement.

The ESA is to assist a shift from gear into neutral. Going into gear should not require any ESA involvement.... whether Merc A drive or Cobra.

The reason that you feel this more so while in the water, is prop thrust, of which actually causes the dog teeth to remain engaged, and by design.

While moving slowly and in gear, the propeller is trying to move the hull faster than what the actual picth would induce if no hull friction.

That is the resistance!

And that resistance is what we need to over-come while making this shift into neutral.

The ESA allows for this shift by momentarily reducing RPM, and therefor reducing prop thrust and Dog Teeth resistance against disengagement.

I'm sure that you know these shifts must be done sharply and crisply.... no fooling around... do it quickly and concisely, or it won't disengage without a fight!

From what I understand, if the ESA is adjusted correctly, the lower shift cable is often the issue.

.

[Guest]

Oh how we LOVE our OMC's !! I had this same problem last year !!! I had to cycle the throttle/controller thru its ENTIRE front to back range to get it to disengage from reverse. Went into gear fine (Forward), but was a bear to get into reverse. And when it got into reverse, was a nightmare to get back into neutral. My marina's mechanic "Tom" (A Great HONEST Mechanic) , figured out the problem. It was the little "End" ferrell or stop on the end of my shift cable. Seems it worked itself somewhat loose and then the cable was able to "SLIDE" inside the "ferrell/ stop on the end" and not fully engage either forwards or backwards. Tom put a new end on the cable, and Wha La - FIXED without any future problems so far. So in my humble opinion , have a competent mechanic check for this 1st. This was only a $ 70.00 fix for me including labor. Hope your problem is as simple as mine.

Prplemke1

1988 Bayliner 2655 Sunbridge

[Guest]

I haven't found the Seloc to be particularly useful, so I sent you a PM to rectify that issue.

Maybe the ESA switch is making going into gear as you stated, but may be misadjusted for coming out of gear. I would check that.

Then as Bounty said, the lower shift cable is the one that usually gets stiff and causes poor shifts. If you replaced the upper shift cable, but not the lower, then the lower may be at fault. If the lower is the original '88 cable then it should be replaced for certain. You will need to remove the drive to check/replace that cable (not a big deal if you are handy and build a cradle).

I would then do all the cable/cable throw/ESA adjustments in the OEM manual. Then check the hard shifting troubleshooting table in the OEM manual if it is still shifting poorly.

[Guest]

OMC shift adjustments are particular. The authority on the subject is Stewart Hastings. You can read his article on OMC Sterndrives here http://canadianboatownersclub.ca/ind...ch-info-part-1 I hope it helps I have the same drives and they are finiky

[Guest]

Update, the ESA switch is working properly, the issue is that the arm with the cams on it is not. It activates the switch going into reverse, but not when going into forward. I measured the length and it appears to be close enough that it should work. Any suggestions?

[2850Bounty]

Wingnutt wrote:
Update, the ESA switch is working properly, the issue is that the arm with the cams on it is not.

It activates the switch going into reverse, but not when going into forward. I measured the length and it appears to be close enough that it should work. Any suggestions?

The return spring, or back-to-center spring, should offer equal resistance in either direction. This is due to the Dog Teeth being cut similarly for both FWD and REV gear engagement.

IOW, given the same prop thrust, the resistance for disengagement should be equal.

What this may mean..... is that the actual shift cable is requiring more force while making a Reverse Engagement than it does for a FWD engagement.

But again.... this system is designed to aid in a shift From Gear back into Neutral (i.e., disengagement) ...... not necessarily for gear engagement.

I too would suggest reading Stuart Hastings.

.

[dktool]

If everything is moving freely and properly adjusted, the interupt cam arm SHOULD NOT move when going INTO gear, ONLY when coming OUT of gear and only when there is a load on it. Driveway shifting is quite useless in determining if things are adjust correct.

Mine was the same as your when I bought it. After much tinkering and adjustment it now shifts better than any Mercruiser outdrive I every drove.

In my case it was zero cost.

As mentioned, use the Hasting reference as a very good knowledge base, then think beyond that.

Stuart mentioned about the cable retainer plate at the slide in the gimbal housing not having the threaded hole tapped straight and would cause the cable to bind when it was tightened to the slide.

What I found on mine was the same issue but it was due to the end surface of the slide not being 90 degrees to the cable bore.

I milled the end of the slide square and that was my cure.

The rest was just adjustment of the shift rod and the cables at the interupt, and the switch cams.

[Guest]

Wingnutt wrote:
Update, the ESA switch is working properly, the issue is that the arm with the cams on it is not. It activates the switch going into reverse, but not when going into forward. I measured the length and it appears to be close enough that it should work. Any suggestions?

The OEM Manual will have the correct troubleshooting procedures.

[Chief_Alen]

http://www.crowleymarine.com/product_support/omc/mechanical.cfm

Click on the link... then on nominal neutral adjustment.

[Guest]

dktool wrote:
If everything is moving freely and properly adjusted, the interupt cam arm SHOULD NOT move when going INTO gear, ONLY when coming OUT of gear and only when there is a load on it. Driveway shifting is quite useless in determining if things are adjust correct.

Mine was the same as your when I bought it. After much tinkering and adjustment it now shifts better than any Mercruiser outdrive I every drove.

In my case it was zero cost.

As mentioned, use the Hasting reference as a very good knowledge base, then think beyond that.

Stuart mentioned about the cable retainer plate at the slide in the gimbal housing not having the threaded hole tapped straight and would cause the cable to bind when it was tightened to the slide.

What I found on mine was the same issue but it was due to the end surface of the slide not being 90 degrees to the cable bore.

I milled the end of the slide square and that was my cure.

The rest was just adjustment of the shift rod and the cables at the interupt, and the switch cams.

Driveway shifting will not help adjust whether or not the lower unit is shifting properly, but you can easily fix ESA issues in this manner if the drive is shifting properly, which it seems it is.

The job of the interrupt switch is to tell the ESA to stumble the engine (lowering RPM/torque) when you shift out of AND in to gear. Yes, in to gear as well. The main purpose is when you shift out of gear, to take the load off so the clutches can easily come apart... as has been mentioned. But it also lowers RPM to make the shift into gear softer on all the drive internals.

To understand what's wrong, you have to first understand what the cam does. As you move the shifter out of neutral and towards a gear, the cam moves and hits the interrupter switch, stumbling the engine. The reverse happens as you come out of gear, making it possible to easily shift out of gear. As you continue to push the shift level, the overstrike switch opens to "cancel out" the interrupter so that it is not firing in gear. If it's firing in gear (overstroke switch shot), you would get stumbles and the engine would die as you applied power. With it not firing, you have the issue you see of not being able to get out of gear.

The ESA problems alone are easy to fix. Disconnect the microswitch harness from the ESA, and put your multimeter leads in each occupied hole as you can see from the ESA if it's newer. They changed the way these were wired - I don't recall which is which, but on the older units there were four wires... the new units have a jumper on the ESA connecting the two switches together, providing only a single open or closed circuit to the ESA.

With the meter on the continuity function so it beeps, go to the helm and shift. What you SHOULD hear is that just as you move the lever to get into a gear, there is continuity for a second and then it immediately stops as you get into gear. The same as you come out of gear - right when you're about to hit neutral, your meter should beep and then stop in neutral. Make the necessary adjustments. Have a helper come and shift while you watch to see exactly how the cam acts on the switches and it will make sense. Each little "point" on the cam represents where you'll hear a beep when it contacts the interrupter. You can easily make the adjustments you need and test without the engine running/etc.

I had to figure this out as our VERY well-respected local mechanic got the shifting right but could never make the ESAs work correctly... and knowing how everything works now, it's quite simple.

[2850Bounty]

ishiboo wrote:


The job of the interrupt switch is to tell the ESA to stumble the engine (lowering RPM/torque) when you shift out of AND in to gear. Yes, in to gear as well. The main purpose is when you shift out of gear, to take the load off so the clutches can easily come apart... as has been mentioned. But it also lowers RPM to make the shift into gear softer on all the drive internals.

I have to agree with Dean.

But as you suggest, the ESA may function while making a shift into gear when there is resistance at the lower shift cable.

If all is working well, the cable resistance for gear engagement should be minimal.

Again... if all is working correctly.

Merc's SI and OMC's ESA would not even be necessary if the Dog Clutch assembly would release easily under prop thrust.

.

[dktool]

If the interupt switch is still made when it is in gear, it is not adjusted correct. The overstroke switch is there for, as the name implies, if it is traveling too far (over stroke) it is a device designed to compensate for improper adjust, a safety if you will, to ensure the boat keeps moving on all cylinders.

As Rick said, it it all based on lower cable, (slide and shift rod resistance too). If there is enough resistant generated going into gear to trip the switch then that is too much.

[Guest]

dktool wrote:
If the interupt switch is still made when it is in gear, it is not adjusted correct. The overstroke switch is there for, as the name implies, if it is traveling too far (over stroke) it is a device designed to compensate for improper adjust, a safety if you will, to ensure the boat keeps moving on all cylinders.

As Rick said, it it all based on lower cable, (slide and shift rod resistance too). If there is enough resistant generated going into gear to trip the switch then that is too much.

Based on? Not quite... it's just a factor in how everything works. On a new/rebuilt sterndrive perhaps everything would work perfectly, but as these units have aged (most are 20+ years old now!) the ideal practices of adjusting them are just that - ideal. The switches are acted on directly by the cam, if things are not set up correctly on that end, the ESA will never function properly. If the drive is shifting perfectly but just not activating the ESA correctly, it can be corrected or at the least compensated for at the shift bracket. This isn't bad - if it is fully engaging forward and reverse without issue, it's fine, even if there is some increased resistance. What you don't want is it coming out of gear, i.e. not fully engaging., or the issue the OP has - the ESA stumbling when it's not supposed to.

No issues with getting the drive to shift properly first, and then fixing the ESA on the bracket, if it's possible. The stuff on the bracket goes out of adjustment too, and gets fooled with by people who don't know what they're doing when there ARE shift cable issues. It's futile to assume you can solve everything with one half of the puzzle.

[Guest]

Just for clarification, I'd like to know if part of the problem is that it is not holding the adjustment when it is adjusted properly. Meaning, after adjustment, does it work right for awhile in the water and then go out again? Or is it not possible to ever adjust it to work correctly?