bearings for 1955 25hp

[orlandoclippertim]

I have a 1954,1955 or 1956 (cant remember which) 25 HP parts motor. I was noticing that at TDC I could rotate the flywheel about 3/4 inch wothout the piston moving. I guessed that there must be some slack in the bearings somewhere. So took the powerhead completely appart to try to restore it- or at least see what was up----
It has needles on the crank, needles on the lower rod, and some kind of plain bearing at the piston pin either brass or bronze. It appears visualy that there might be more slack in the bushings than in the needles - maybe both worn (?) and bushing worn more.
I would be happy to replace the needles too .......
I am wndering if yall have suggestions for the bushings as to where to get them (will any bushing with the same dimentions work- are they babbit or bronze ?)
also if yass can fill me in on the avilability of the needles ?

Also- the crank has a needle bearing right in the middle of the crank - how do you get the needles out ? looks like you should be able to slide the cage sideways and get them out - but the cage wont seem to slide quite enough .......

Thanks in advance for you help !

Tim in orlando

 

[F_R]

Re: bearings for 1955 25hp

In the first place, some over-center movement at TDC is normal because the crankpin is moving sideways, not pulling or pushing on the piston. OK, the wrist pin bushings are not replaceable. Well I suppose you could have a machinist do it and line bore them. There is a snap ring around the center bearing. Remove the snap ring and the bearing comes apart.

marineengine.com may have the needles you are looking for.

 

[orlandoclippertim]

Re: bearings for 1955 25hp

In the first place, some over-center movement at TDC is normal because the crankpin is moving sideways, not pulling or pushing on the piston. OK, the wrist pin bushings are not replaceable. Well I suppose you could have a machinist do it and line bore them. There is a snap ring around the center bearing. Remove the snap ring and the bearing comes apart.

marineengine.com may have the needles you are looking for.

Thanks "supreme" for the info.

Yes, i was aware that a little movement there is due to the geometry at TDC. However i have another 55 25hp which loods to be in better shape and was running. I could move it about 3/8 at TDC where I could move the parts motor about 3 times that - maybe 4 times. What makes the bearings in the top of the rod "non-replacable" - are they shrunk fit into the rod end ? Dont see how they could be in an aluminum rod which I would think must be heat treated (heating the rod would ruin the heat treatment)- so i would think it would have to be a interference fit - like press in and press out. i have not taken the rods out of the pistons yet as I have to electric pensil them so i dont mix them up later. i guess I could tell the difference from babbit and bronze by color. I notice I can tilt the rod a little on the wrist pin which seems to indicate more wear that you would like.......

Tim

 

[F_R]

Re: bearings for 1955 25hp

By "non-replaceable" I meant that OMC did not supply them as separate parts. They were bronze and yes they did wear considerably. They actually were too small for the loads placed on them. You definitly do not want to cheat on the oil mix. 24:1. The rods are steel, not aluminum, and yes the bushings are pressed in. If you want to have a machinist fabricate new bushings, use 932 (660) bearing bronze. They must be bored absolutely parallel with the rod's big end after installation, the reason OMC didn't supply replacement bushings.

I am assuming you really do have a 25hp. The 1956 was 30hp and had needle bearings in the wrist pin end. They were too small too, and often came apart and ruined the powerhead.