omc 800 mechanical shift

[shimano]

I have a 79 omc 800 mechanical shift.Won't go in to forward or reverse,Shifted fine when put away last fall,now nothing.Suspecting lower cable,should I look elsewhere?

 

[Howard Sterndrive]

Re: omc 800 mechanical shift

79 was hydromechanical.
full mech wasn't until 1981.

if it spent the winter with water in the lower unit oil, it is likely the hydraulic shift assist mechanism in the lower is seized/rusted

 

[shimano]

Re: omc 800 mechanical shift

The boat is a 79 but did not come with the original motor&drive,then the drive was replaced with one off a 1981 I think.There is only a shift cable to remove the lower.I'm not sure how to tell the diff beetween the full mech one and the hyd assist one.It sat the winter with the lower empty so if it is hyd assist i could see the mechanism being rusty,is this a hard fix?

 

[Howard Sterndrive]

Re: omc 800 mechanical shift

I'm not sure how to tell the diff beetween the full mech one and the hyd assist one.

see the rectangular zinc anode in this pic below the V6 decal next to the idle relief holes... it is only on full mechanical. the hydromech drive looks identical except no rectangular anode:

,is this a hard fix?

fairly

 

[wire2]

Re: omc 800 mechanical shift

Assuming it is a post '81, you should establish if the problem is before or after the shift converter. Remove the ?" bolt from the shaft, lift the bracket off the square post, remove the slot screws, lift the cover off.

There's a ratchet pawl where the twin cable enters from the right side, slide a screwdriver in to open the pawls. Push the twin cable in to get some slack and undo the 2 steel wires from the quadrant piece, then remove the twin cable from the converter. Alternatlely pull one, then the other. That *should* effect a shift from F to R. If it does, the problem is in the control box or cables.

When putting the steel wires back, make sure they don't cross.

 

[shimano]

Re: omc 800 mechanical shift

If it is hyd assist ,Does it run off the oil in the lower unit,Could improper levels affect shifting?

 

[Howard Sterndrive]

Re: omc 800 mechanical shift

If it is hyd assist ,Does it run off the oil in the lower unit,Could improper levels affect shifting?

yes, and not sure....

it should still shift mechanically. the hydro assist was just a booster to make shifting easier.... and easier on the cable

 

[full stringer]

Re: omc 800 mechanical shift

how soon did you notice the problem before or after you put it in the water i say this because your problem may or may not be the cable if it is indeed a full mechanical shift if you put it in the water and shifted it under load you could have either stripped the water pump shaft splines or the bearing carrier shaft splines that connect to the lower unit vertical drive shaft or possibly broke the vertical drive shaft itself in the lower. if you do as howard sterndrive says and remove the shift converter cover and cables trying them by hand and the prop doesn't lock in gear you'll have to split the outdrive cases and look at the shafts believe me a broken shaft will be easier on your pocket book than a cable$$$$ good luck

 

[shimano]

Re: omc 800 mechanical shift

I tried moving the shift arm by hand(on the back of the motor with the cable from the handle removed)When I shifted it forward or reverse,the prop never locked up it got harder to turn though,Im going to take the control box apart today to check the cable to see if it is the cable or something else.I'll repost later today with what i found,thanks for the help

 

[shimano]

Re: omc 800 mechanical shift

Took it apart this morning,It did indeed end up being a mechanical shift (it has the anode).Ended up being the water pump shaft (top end).Splines gone ,I guess we would have seen it heat up if we would have let her run longer.I stuck my finger up in the shaft on the upper the grooves seem ok,Wondering about getting away with just a new water pump shaft?Also,Would the shift interupter be on the control box(where the lower shift cable connects to the upper one).I'm thinking they didn't do the retrofit correct(reason for stripped shaft)?

 

[wire2]

Re: omc 800 mechanical shift

The shift interrupt module is on the engine, (black, ~2" wide, 4" long) and the switch to activate it is on the converter, along with the neutral start switch.

 

[full stringer]

Re: omc 800 mechanical shift

Took it apart this morning,It did indeed end up being a mechanical shift (it has the anode).Ended up being the water pump shaft (top end).Splines gone ,I guess we would have seen it heat up if we would have let her run longer.I stuck my finger up in the shaft on the upper the grooves seem ok,Wondering about getting away with just a new water pump shaft?Also,Would the shift interupter be on the control box(where the lower shift cable connects to the upper one).I'm thinking they didn't do the retrofit correct(reason for stripped shaft)?

they probably didnt add the spline shaft seal the seal with the grooves that slips over the shaft and glue it in place. also you need special spline grease for those shafts or else rippp boom!! as for you checking the bearing carrier shaft in the upper and you say feels good, you can risk it leaving it in however a new one with a new water pump shaft would mate them better together during initial break in but it's your boat. good luck to you and happy boating

 

[full stringer]

Re: omc 800 mechanical shift

hey shimano i was curious as well, you wouldnt be running a stainless prop would you? reason i ask is im considering removing mine on my 800 and go back to aluminum im hearing alot of controversy that the omc shafts cant handle the extra weight see ya

 

[shimano]

Re: omc 800 mechanical shift

Told him the upper shaft is questionable,It mates ok but there is a little play,He got the shaft used and decided to just try it,The seal and circlip were missing off the old one but I put them both on the new one with a little grease.(If it goes again he'll have to relace both).He also is running a stainless prop,Maybe if he switches back to alloy he'll prolong his season.

 

[wire2]

Re: omc 800 mechanical shift

hey shimano i was curious as well, you wouldnt be running a stainless prop would you? reason i ask is im considering removing mine on my 800 and go back to aluminum im hearing alot of controversy that the omc shafts cant handle the extra weight see ya

I don't think a ss prop is an issue with shaft strength. I ran the factory SST stainless from '84 up to '07 on the original shafts. Even when I experimented with a TPI idling at 850 rpm, shifts went in hard (and wouldn't come out again) but still no issue.

I believe shaft failures are largely due to striking underwater objects with the prop.

 

[shimano]

Re: omc 800 mechanical shift

This one did not have the rubber seal on the water pump shaft,corrosion probably added to the failure

 

[full stringer]

Re: omc 800 mechanical shift

thats right uh huh??