more hydroelectric problems

[ddaigle]

took apart my 1970? 3 cylinder hydroe lower unit, everything looked ok, but clutch dog will not engage forward gear. measured everything and pump piston appears to be too long. Are there different length pistons-plungers? Have never seen this motor work in forward, got it from a friends diceased father, son knows nothing about it. this is very strange, looks like lu was recently rebuilt, maybe wrong parts? Have measured several times all the way to back of pump and always too long. Thanks

 

[R.Johnson]

Re: more hydroelectric problems

Are you sure the piston is going all the way to the bottom of the bore in the pump housing? There is an O-ring in the piston bore, is the piston hanging up here?

 

[ddaigle]

Re: more hydroelectric problems

took the piston out and measured from very back of piston cavity to front of gear, then measured length of assembled piston and prop shaft. piston is too long to allow clutch dog to engage gear.

 

[DHPMARINE]

Re: more hydroelectric problems

ddaigle,All you can do is find a known correct piston and compare.OMC had different lower units thru the years,and no manual that I know of lists a piston length.Is the pump located properly?It should be held in by a large snap ring,and maybe there should be a strainer (sreen) between it and the pump.DHP

 

[ddaigle]

Re: more hydroelectric problems

This lower unit has me baffled. According to the explanations in the manual this lowerunit seems to have parts from different motors. It has the lower driveshaft bearing and driveshaft shims etc. that the manual says only a 1972 v4 motor has. This is a 3 cylinder, and it seems to have the pump that has no c ring in front of it. It seems to be seated properly as everthing else ligns up(shifter rod, etc.) and i had reverse and nuetral but no forward. I am about to throw this thing in the bay.

 

[R.Johnson]

Re: more hydroelectric problems

Your 60 3 cyl. shares the same pump housing cap as the 85, and 115 V-4's. This cap has the piston bore machined in. Your engines piston has a different part number. The V-4's have the same piston number. Your unit may well have a V-4 piston in it. The 3 engines sharing the same pump cap means the piston's on the piston end are the same diameter. but the lenghts would be different. They do not give the lengths in the spec.'s Let me see if I can find a v-4 piston, and I will give you the length.

 

[R.Johnson]

Re: more hydroelectric problems

A v-4 piston measures 3.235, see how this compares, and let us know.

 

[ddaigle]

Re: more hydroelectric problems

Wow! that makes sense! You may have saved my sanity. Let me know what you find out. Thanks mucho.

 

[R.Johnson]

Re: more hydroelectric problems

The part no. of the piston you need is 315709, it was last available in 1993 at a cost of $123.00. So much for saving your sanity. Hopefully someone here has one. Can you determine how long the piston has to be? if no one has one, I may know a way out here.

 

[ddaigle]

Re: more hydroelectric problems

I am at work so can't check right now, but as i recall needs to be almost exactly the length of engagement ears on clutchdog, roughly 1/4 to 3/8of an inch. Thought about cutting it down if feasible.

 

[R.Johnson]

Re: more hydroelectric problems

To measure, try this! With the oil pump, and all componets removed, take the clutch dog spring out of the prop shaft. With everything assembled, including the piston, set it up on a bench just as it would be in the gearcase. Push the clutch dog forward until stopped by the piston, measure from the face of the clutch dog lug to the inner face of the forward gear. This should be the length to remove from piston stem. Look also at your piston stem where it contacts the plunger on the clutch dog. Is it undercut for about an inch in length? This may cause a problem by letting the piston stem get misaligned on the prop shaft bore if you shorten it. Of course! this all depends on if you can find the correct piston. Before someone calls this a make shift repair, we are talking a 34 year old engine here.

 

[ddaigle]

Re: more hydroelectric problems

RJohnson, Thanks so much for info. It turns out that I have the right piston-(short one). Mechanic at dealer was as stumped as me even called omc rep. I went home and said what the heck and put it back together. Amazing, right now it works! Weird thing is that bearing carrier seems to be farther in than before. Maybe this was the problem to start with. Still cofused about it.

 

[R.Johnson]

Re: more hydroelectric problems

The prop shaft bearing carrier has a large O-ring on the inner diameter of the carrier. The gear case has a stepped shoulder that this end of the carrier slips into, to give a seal. If the carrier did'nt slip into this inner surface you would have a lot of prop shaft end play, and would give you the problem you discribe. Be sure end put gasket sealer around the head of the four bolts that hold the carrier. Sound's like you have the problem solved, good going.