Help with a 1976 402 40HP Mercury

[dfishingguy]

Hi y'all

I need some help with my 40HP mercury. I believe it is a 1976, it is a 402 40HP.

Ok here is what happened. I was idleing away from the ramp and decide to give it full power, I went about 15 feet when all the sudden it popped out of gear and the engine reved up. The motor did not die but I no longer had foward or reverse gears.

Naturally I thought the lower unit just went tits up on me. I pulled the boat off the lake and went home. I dropped the lower unit to inspect the damage. To my surprize the lower unit gears look just fine. I noticed some water in the lower unit oil and decided to change out the water pump, seals and impeller while I had the lower unit off.

I went in to a local shop and took the lower unit gears with me so they could take a look and tell me if anything looked broken. The mechanic told me the cluth dog looked a little worn but he has seen worse. He told me to check my gear cable to makes sure the they are not out of adjustment.

So I get home, put every thing back together. I put the lower unit back in place and hook up the water muffs to check if the motor some how fixed itself. When I fire up the motor I can hear a loud chattering which seems to come from the mid section of the motor. I also notice the motor is not peeing when hooked up to the muffs with water running. This is getting a bit fustrating.

So my question to you is... is it possible the I put the impeller in backwards? Can his be the reason the motor is not peeing?
Second... could there possibly be a problem with the drive shaft teeth which fit into the upper part of the motor and that is the chattering I am hearing.

When I put the motor in gear (forward or reverse) the prop will turn just barely. I am conserned the drive shaft is not turning.

I have adjusted the gear cable and have ordered and new one, although I do not think this is the problem now. Do you think the clutch dog needs to be replaced? When I put the motor in gear I can not turn the prop by hand so that tells me the gear is engaged. I am wondering now if I have a drive shaft problem.

Any suggestions would be a great help. I am in limbo now and not sure where to look next.

Thanks

 

[Laddies]

Re: Help with a 1976 402 40HP Mercury

It sounds like you lost the spines in the crank or driveshaft, when in the lake in gear and the unit won't move ck for water flow if it stops the problem is in the driveshaft area, if it pumps water the problem is below the w/pump.

 

[dfishingguy]

Re: Help with a 1976 402 40HP Mercury

Hi Laddies

You are the second person to tell me to take a look at the drive shaft splines so that is what I am going to do. When I had the lower unit off the first time I notice carbon had built up on the drive shaft splines so I cleaned them off a bit. I am going to pull the lower unit off again this morning and take a good look. Have you aver heard of a problem where the splines go bad? Seems like an odd thing to happen.

Thanks for the help. I will let you know what I find.

Dan

 

[Laddies]

Re: Help with a 1976 402 40HP Mercury

It's not a uncommon problem when the splines are not grease when the unit is off or in corrosive water.

 

[dfishingguy]

Re: Help with a 1976 402 40HP Mercury

Well it looks like you are right. The splines inside the motor look to be rounded and smooth. The splines on the drive shaft look to be in ok shape but I wonder if the drive shaft should be replaced too.

So what to do next. I really want to fix this motor; it has been very good to me the last five years I have owned it. How do I get to the part where the drive shaft connects? Is it possible the get to this part thru the middle part of the motor or do I have to go thru the power head?

I do have a mercury manual for this motor but unfortunantly it does not cover this section. I know that a person can buy chilton manuals online from automobiles; is the a manual that goes into more detail that can be bought online?

This looks to be a complex part to fix and I wonder if it is above my level of fixing. I would like to do the work myself.

Any help would be great.

Dan

 

[jpmurphy]

Re: Help with a 1976 402 40HP Mercury

Can't tell if you every got anymore replies to your problem. If you need more manuals, especially a service manual which is what the repair folks use go to: OldMercs.com.

This site has everything you could imagine.

Good Luck
Murph in Kansas