OMC 400 issues

Shreegs

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Mar 4, 2017
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So I'm the proud owner of an early 80s cobia with the 2.5 motor and 400 sterndrive. I got it really cheap and now I know why. I'm a lifetime reasonably accomplished mechanic but this is my first venture into boats. I got the engine running like a dream, but today when I went to put it into gear ...nothing happened. So I've been looking at every link and website I can find for hours trying to figure out where to get started. Through this research I determined that I have an older Hydro mechanical shift mechanism. Someone told me that there should not be 90 weight gear oil in the lower unit which it looks like there is... and that can be a problem so I thought I would start there. I'm also reading that it seems the way to go is to switch it out to a fully mechanical shift lower unit... but that requires a new set of cables and control to match. Then I read that you can modify your existing cables but there was no detail on how to do that . So I'm just looking to get some input from some experts and possibly reach out to see if anybody knows where I can get those parts at a reasonable price. By the looks of my ball gears this things got alot of hours on it so it might behove me to just replace the whole thing if I can find a decent used one. Any input would be greatly appreciated .
 

superbenk

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Oct 27, 2008
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Both the full mechanical & hydro-mechanical take the 90w oil in all 3 gear cases. The electric shifts required a special oil in the lower unit due to the requirement the lubricant not be conductive (due to the solenoid shifting mechanism).

Switching to a full mechanical shift requires the electronics to retard the engine briefly during shifts to allow the unit to shift properly. This included micro switches on the shift converter box & a module that would arrest the spark briefly during the shifting. I'm not sure what would be involved in the conversion of an existing hydro-mechanical mechanism other than replacing with these full-mechanical pieces. No idea about the cable differences - I thought they were the same, but I have no idea.

Some of these parts are going to get difficult & expensive to source. Full-mechanical shift is the preferred way to go (as far as I know) so they might be tough to get your hands on with all the bits. Shift cables are consistently really expensive (~$600 when I had my OMC a few years ago) and not always easy to find in the correct lengths.

If your ball gears are well worn, I'd definitely be replacing those before using as worn gears can put stress on shaft bearings & seals causing them to wear out. If you didn't know this already, never run your boat with the drive tilted up at all. It should only be run with the drive fully down. Trim is done via a jackscrew on the front motor mount which adjusts the angle of the engine & outdrive as a single unit. Running the engine with the drive tilted up at all will wear out the ball gears & potentially cause other damage.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Jul 23, 2011
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You need to accurately identify the outdrive. If tou have a 1980 or earlier, you most likely have the hydro-mechanical drive (painted white). 1981 to 1985 was the mechanical shift (painted light silver/grey)

Things that can go awry are the ball gears and shift cables as mentioned, however the multi-piece vertical driveshaft is also a problem and known to have the splines strip out.
 

southkogs

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Jul 7, 2010
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Figure out what ya' have going on before you start exploring major changes ... I did similar to you with my first I/O boat, bought an electric shift Stringer. Thought I had a major problem on my hands (which the seller thought too), and it turned out to be an electrical glitch that fixed pretty easily.

The Stringer has a bad rep, and certainly has it's quirks. But if it's runnin' and you can easily keep it runnin' - they're really pretty decent drives.

When you're running the engine, the ball gears aren't bad enough that the upper gear case isn't turning, right? If that's correct, you're probably (mostly) okay down to the lower unit. Change out the gear oil up top and make sure there's not any metal flakes in it.

Have you changed the impeller? If not, do that and check the shaft that's there (the one Scott's talkin' about). Those babies strip out often enough that you may find it's just that shaft.

Welcome aboard.
 

Shreegs

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Mar 4, 2017
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Thankyou, I'm going to take the drive off and open her up. I definitely have the white one, so it's earlier than the boat year of 1983... makes me wonder if they did the correct things with the cables when they converted it to the hydro/mechanical. They fed me a line of BS when I bought it and said that it was running last year, by the looks of the fuel system she probably hadn't run for five years minimum. I have a clymer manual, but it leaves alot to be desired. The ball gear on the upper is spinning, so that stripped shaft sounds very plausible. Im sure it needs an impeller, so I need to get in there anyway. I'm actually finding the parts for these things are pretty reasonable on eBay, i've just never done it so I'm a little apprehensive but there's only one way to learn right ?
 

southkogs

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Hunt ya' up a good shop manual. You're gonna' need it - Clymer will get ya' there, but for the Stringer the real deal is MUCH better.
 

Shreegs

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Mar 4, 2017
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Well I got everything torn apart today, looks like I'm in luck...the gearboxes appear to be in good condition... The shift cable was not working correctly, all gummed up and is seized up. When I engage the shift mechanism in the lower unit it goes into forward and reverse. So it looks like a water pump kit couple gaskets and O-rings and I'm good to go with the new cable. This wasn't nearly as difficult as I thought it was going to be...funky design with that shift cable running through all three pieces of the outdrive šŸ˜µ
 

Shreegs

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OMC Stringer Shift Cap & Cable Install
Shift Housing Disassembly and Assembly
1. Remove shift housing cover screws and lockwashers. lift off the cover and discard the gasket.
2. With a screwdriver pry out the pinion shaft retainer. Discard the O-ring.
3. With Special Tool Part No. 909881. pull out the pinion shaft seals, bearing, and washer by threading the tool onto the end of the shaft. Discard the pinion shaft umbrella seal. O-ring. and plastic washer.
4. Lift out the drive pulley and remove the shift cable pucks from the slots. Note the difference in the size of the cable pucks and the direction the core wires wrap around the pulley.
5. Using side cutter pliers pry out the idler pulley shaft. Discard the quad-ring. Lift out the pulley and two washers.
6. Remove two cable retainer screws and discard. Note the position of the retainer tab. then pullout shift cable.
7. Clean sealer off housing with solvent.
Inspection Procedure
1. Clean all parts (except cable) in solvent and dry thoroughly.
2. Inspect shift housing and cover for cracks, nicks or burrs, especially on gasket faces.
3. Inspect the bearings for corrosion or damage. Replace as required.
4. Inspect shift cable for cracks and frayed or kinked core wires. Shift cable core wires damaged by fraying or severe kinking must be replaced. Continued use of shift cable with damaged core wires may result in core wire breakage, causing operator to lose control of boat.
5. Inspect the pinion shaft rack teeth and splines forchips. burrs or corrosion that would prevent proper engagement.
Change Hydromechanical Cap for use in Full Mechanical installation.
On the underside of the cap are two tabs that extend down. The tabs should be cut flush with the bottom of the cap to allow installation and avoid interference with shifting.

Reassembly
All of the parts in this assembly are vital operating parts and must be properly installed and secured.If part replacement is necessary use only OMC parts specifically designed for this application.Improper assembly sequence, failure to use all parts and/or substitution of parts designated for this assembly may cause shift malfunction or loss of start in gear protection and may cause operator to lose control of boat.

1. Lubricate retainer with soapy water and place the retainer on the new shift cable: When properly attached. index rib of cable will be at open end of retainer slot.
2. Insure that cables are parallel and insert into shift housing.
3. Feed small puck and cable into idler pulley chamber.
4. Feed other cable into drive pulley chamber.
5. Install retainer and new lock patch screws. Tighten screws to a torque of 5-7 ft. Ibs. (7-9 N.m).
6. Grease the idler pulley bearing with OMC Extreme Pressure Grease or equivalent. Place a new quad-ring on the idler pulley shaft, and lubricate with gearcase oil. Install the pin, washer, pulley, and washer in that order. Push shaft thru pulley into the housing., spin pulley and see if it turns freely, then seat the shaft with a hammer. Do not drive pin removal groove below housing surface. Make sure the shift cable wire with the small puck end runs under the idler pulley. See Figure 7-1-49.
7. Grease the pinion shaft bearings (one on the shaft and one in the shift housing) with OMC Extreme Pressure Grease or equivalent.
8. Coat a new pinion shaft O-ring and a new umbrella seal with OMC Triple-Guard Grease, press O-ring into seal.
9. With Special Tool Part No. 909967, install the umbrella seal and O-ring (umbrella seal must face away from pinion gear) onto the pinion shaft.
10. With the drive pulley grooved surface facing the rack support. insert the cable pucks into the pulley.
11. With the cables attached, give the pulley a 1800 twist clockwise. Pull the cable ends and bring the pulley down into the housing.
12. Note the position of the uncut spline on the shaft and insert the shaft, O-ring and seal assembly into the housing.
13. Rotate the pinion gear until the uncut splines align with those of the drive pulley The pulle'y' uncut splines are directly below the large puck hole. Press in on the shaft until nose slides thru pulley and into bearing.
14. Place a new washer onto the shaft so that washer rests against the pinion gear.
15. With Special Tool Part No. 909882, install the bearing by presSing against lettered side of bearing. Special Tool will set bearing to the correct depth: when it seats against housing.
16. After installation make sure the umbrella seal lips are not folded under.
17. Install a new O-ring on the retainer. Coat O-ring with OMC Gasket Sealing Compound. Push retainer into shift housing until it seats.
18. Before installing cover, make sure shift wires run parallel under pulleys and do not cross. Coat both sides of the cover gasket with OMC Gasket Sealing Compound. Replace the cover, gasket, four screws, and washers. Tighten screws to a torque of 7-10 in. Ibs. (0.8-1.0 N.m).
19. Prior to assembly to the lower gearcase, pressure and vacuum test the shift housing assembly for leakage. This will prevent the installation of a shift housing assembly with a bad pinion shaft seal or shift cable assembly. To perform this test. use the hose and clamps required for pressure checking the lower unit. Attach one end of the hose on the three sealing ribs halfway down the cable, the other to a gearcase pressure tester. Pressurize the assembly to 3-5 psi (27-34 kPa) for 5 minutes. No drop in pressure should be realized.
20. Next, attach a gearcase vacuum tester to the hose. Pull vacuum to 3-5 Inches of mercury for 5 minutes. No loss of vacuum should be realized.
Installation of Shift Housing Assembly
1. Coat both sides of a new shift housing gasket with OMC Gasket Sealing Compound and place it on the gearcase.
2. Before installing the shift housing and cable assembly, pull the long cable out as far as it will go. The short cable should be completely seated, and should measure approximately 4-7/8" to center of puck. See dimension "A" in
3. With long cable fully extended, position shift housing over the shift rod and engage rack with pinion in shift hbusing by pulling on short cable while maintaining tension on long cable.
4. Forward cable Will lengthen, and reverse cable will shorten durring installation.
5. Hold flange of shift housing as near parallel to gearcase mounting flange to provide for engaging the correct pinion tooth.
6. Install SIX shift cable housing screws dipped in OMC Gasket Sealing Compound or equivalent, and torque tq 60-70 in. Ibs. (6.8-9.4 N.m).
7. After shift housing installation on gearcase, the cable mean distance travel must be checked as follows:
8. While rotating drive,shaft by hand, shift the unit into forward gear by pulling on the short cable Measure "A" dimension to center of puck.
9. Shift into reverse gear (long cable) and remeasure "A" on short cable to center of puck.
10. The mean distance ( "A1"+ "A2" )/2 must fall within 7-5/32 to 7-29/32" (18.2 to 20.08cm). If this dimension is not met, disassemble and repeat step 2, changing slightly the 4-7/8" starting dimensions.
Continued assembly of shift cable that does not meet the 7-5/32 to 7-29/32" (18.2 to 20.08cm) dimension may lead to shift stroke restriction at the shift converter housing ard prevent full engagement of the clutch dog. This can result in ratcheting that can damage shift system components.
 

Shreegs

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Mar 4, 2017
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Posted this shift cable assembly instruction from Crowley, I found it after alot of searching. Thought it might help anyone doing this job.
 
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