1957 35hp big twin lower unit

[mntcman]

Took the lower unit off my motor to check impeller. Impeller was very flexible with slight curve to blades and no pieces missing. Gear oil was all milky(water). Unit had no seals on drain and fill plugs. Have not removed skeg yet. Do I have to remove philips head screw in side of unit to remove the skeg? How much free travel should there be between prop shaft and drive shaft? I get about 5/8" free travel between the two.

 

[jbjennings]

Re: 1957 35hp big twin lower unit

Howdy,
welcome to iboats!

You'd be better off replacing the impeller. They're not high and if in good shape, the blades will stick straight out when out of the pump housing.
You'd also be better off replacing all seals and having a knowledgeable person look at the clutch dog and gear ears. You will need to remove the phillips head screw in order to take the skeg off--it is the pivot point for the shifter cradle. I wouldn't remove it unless you're serious about resealing the whole thing. There are parts diagrams and exploded views of your motor online if you need them. Have you ever had the motor at wide open throttle, to prove the clutch dog will hold gear? I'd hate for you to change all seals and reassemble, just to find out it won't hold gear. If you don't know how to remove the shift shaft bushing or prop shaft and drive shaft seals, holler back. An actual OMC service manual would serve you well, rather than seloc or others.
good luck,
JBJ

 

[mntcman]

Re: 1957 35hp big twin lower unit

I just got the service manual in the mail. Yes I have had it wide open before with no noticeable issues. I plan on resealing the whole thing and yes install a new impeller. You are right. It's cheap insurance to replace it at this point. Gonna see if my local shop has the necessary parts. If not I'll order them. Also found an old timer with a complete bottom end he'll let me have for $50. If I run into trouble I'll give you a shout. Thanks for your help.

 

[lindy46]

Re: 1957 35hp big twin lower unit

Pressure test the L/U before buying all the seals - may just have leaked water in at the drain and vent bolts since there were no seals on them. Or just refill the gearcase with fresh oil, replace the seals/washers on the drain and vent bolts, and run for awhile. Then check to see if the oil is milky.

 

[mntcman]

Re: 1957 35hp big twin lower unit

Gotta pull the skeg anyway. Looks like it bottomed out while being towed and has a slight curve to it as well as being "ground down"at the tip.

 

[kfa4303]

Re: 1957 35hp big twin lower unit

If that's the case, you do need to remove the phillips head screw and resign yourself to resealing the gear case. It's not really that bad. You should be able to get the kit right here at iboats for about $15. You may need a seal puller, but that's the only special tool that is required. Taking a few pics along the way can help you remember how everything goes together and you'll be fine.

 

[HighTrim]

Re: 1957 35hp big twin lower unit

I second putting on new drain and vent gaskets when changing the oil then going for a run. You may luck out. Crack it slightly after your run, the water will sit at the bottom and exit first if there is in fact intrusion.

Dont worry about the slight bend/ground down tip too much. All the skeg does is kick the motor up if you hit ground or a rock to preserve it. Not a real problem if it is slightly damaged. If you do end up with water intrusion, reseal the whole thing, come back for advice on this when you are ready, 3M 847 will be your best friend for this, tip #1

 

[mntcman]

Re: 1957 35hp big twin lower unit

New drain and vent gaskets sounds like the way to go. I can always reseal the whole unit if I have to. I'll throw a new impeller at it and try my luck. Thank you all again.

 

[kfa4303]

Re: 1957 35hp big twin lower unit

I agree. Give the gaskets a shot. You might get lucky. High Trim, where can you get 3M 847? Do auto parts store sell them or Wally world, or places like West Marine? Thanks.