fill hole behind prop

C

CanuckChrysler

Recruit
Joined
May 26, 2008
Messages
1
Hi Experts, I am an amateur user and fist time poster. Please forgive my lack of expertise.

I recently purchased an old, but working bass boat. It has an old Chrysler 35 HP, model 3542 on it. Behind the prop, there is a hole, with screw threads on it... but no screw !?!... above the hole it says "fill"....
How do you fill this ?
Does it need a screw ?

The engine runs and prop works, but I think it needs lower unit oil, or at least it should be checked... can anybody offer me some advice, or point me in the right direction? Please advise. Any help would be greatly appreciated. To help, please see pic.
 

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eurolarva

eurolarva

Rear Admiral
Joined
Jun 24, 2003
Messages
4,182
Re: fill hole behind prop

Do not run the motor without gear lube in it. The part can be purchased at a Mercury dealer part number 10-79953Q04 cost is about 4 dollars. It is called a Plug, Gear housing. You will also need a gasket part number 12-191833 which costs less then a buck. When you are there buy a quart of high performance gear oil. It seems as though this is thicker then most gear lubes and less likely to leaking. Check the threads on the screw hole hopefully they are not stripped. I cant tell but from the looks of the pic there is a lot of rust going on. If it is like that inside the lower unit the whole thing might be trashed
 
Jack Daniels

Jack Daniels

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Joined
Sep 21, 2007
Messages
266
Re: fill hole behind prop

If it seems trashed you can try and clean up the threads with a tap and dye set. I just replaced my impeller and alot of the bolt holes needed cleaned out. Worked like a charm, just make sure you use the correct Tap size of the hole because you dont want to recut the threads just clean them up.
 
JB

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: fill hole behind prop

There is another plug, above the bulge, labeled "vent", that uses the same size plug and gasket.

Take the "vent" plug out to fill the gearcase. Pump or squeeze the oil (depending on what container you get) into the gearcase from the "fill" hole until it starts to overflow the "vent" hole. Then replace the "vent" plug with a new gasket, withdraw the oil container and replace the "fill" plug with a new gasket.

The gaskets for these plugs are crushable, use only once, gaskets. Be sure to have a supply on hand.
 
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