1975 omc 235 sterndrive problems

[Monk38]

My friend just bought a 1975 Inca with a 235 omc sterndrive. He put it in the water, it has reverse, neutral, and when he puts it in forward he also gets reverse again. NO FORWARD.

brought it to boat mechanic. He said there is power all the way back to the coil units, and believes one of them is out... He also doesn't want to work on it. in fact no one within a 150 miles wants to work on it " too old they say"

so....... does this diagnosis sound correct? I am fairly mechanically inclined, can I do it myself?

Also, does this lower unit take type c fluid? if so would the wrong fluid cause or contribute to this problem


thanks in advance......

 

[bruceb58]

Re: 1975 omc 235 sterndrive problems

It does take type c fluid but only needed in the lower half. What is in there now?

There are two wires going into the sterndrive. One is forward and the other is reverse. Ground is just done through the drive so very easy to check with a voltmeter.

 

[NW Redneck]

Re: 1975 omc 235 sterndrive problems

Yes, incorrect oil in the lower can cause shifting issues, especially if there is water in the oil. To test the shift coils, un-hook the shift wires at the knife connectors on the inside of the transom, and check resistance with a multimeter from each wire to ground (bare metal anywhere on the drive.) You should have 4.5 to 6.5 ohms on each one. If you read open (no continuity) then the wire is broken somewhere, if the ohm reading is out of spec then the coil is either shorted or bad. Also make sure that the ground wire from the intermediate housing to the upper gearcase is undamaged and connections are clean. If you want to work on the drive yourself, get you a factory OMC manual. The Seloc/Clymer aftermarket ones are OK for simple stuff but not much more than that. It will tell you what special tools & materials/sealants are required. Good luck!

 

[Monk38]

Re: 1975 omc 235 sterndrive problems

thanks, he does have the wrong fluid in the lower unit, I will have him change it and help him check the ohms... I will let you know

 

[Monk38]

Re: 1975 omc 235 sterndrive problems

thought I would check back in.... turns out it was the spring tab in the forward clutch pack. Apparently a fairly common problem on these models. thanks for all your input.

 

[NW Redneck]

Re: 1975 omc 235 sterndrive problems

Glad ya fingered it out. Shouldn't be too hard to fix.

 

[Boomyal]

Re: 1975 omc 235 sterndrive problems

thought I would check back in.... turns out it was the spring tab in the forward clutch pack. Apparently a fairly common problem on these models. thanks for all your input.

It is only a common problem for a few units that you cannot identify the cause of. Those spring tabs do not break unless you encounter a momentary lapse in continuity, under load. Then they snap off. I had this problem repeatedly with my '75 (back in the day) I finally converted to the newer (at that time) hydro-mechanical drive back in 1979.

I have been sailing along with that drive ever since.