merc 7.5 melted switchbox

[saltair]

I just bought a jon boat with a merc 7.5 from a friend of a friend, so I have the option of taking it back. He hadn't run the motor since last summer. Cleaned the carb today and started motor. Starts easy, runs smooth. Compression 120 on both cylinders. Wasn't pumping water so I shut it down until I get an impeller.

Here's the catch. The plastic, tar like filling of the switch box has oozed into the cavities of the pan and down the midsection of the motor. I assume this filling serves a purpose. This had already happened either in storage or the last time he used it. Any idea why this would melt/ dissolve?

Switch boxes are expensive for this motor. Should I just take it back? Also the coils both have tiny cracks in the same spot.

 

[saltair]

Re: merc 7.5 melted switchbox

is this so rare that no one knows anything about it?

 

[saltair]

Re: merc 7.5 melted switchbox

changed impeller, motor runs great. Thinking about a test ride. Any suggestions?

 

[7920hpMercury]

Re: merc 7.5 melted switchbox

Interesting, never seen this and seen a lot of 7.5/9.8/20 switchboxes.

I know you can dissolve the goop by soaking in acetone.

If it runs good, I would goop it up with some high temp auto RTV and run it.

Good luck and good motors!

 

[saltair]

Re: merc 7.5 melted switchbox

thanks, I'll try that before replacing. I talked to a mechanic yesterday who said the filling was mainly for vibration and protection from the elements. It is super sticky almost like the asphaltum they used in printing.

He said he had seen a few that got soft, but never one that just dissolved like that. I'll try mineral spirits first and work my way up to acetone.

 

[d.boat]

Re: merc 7.5 melted switchbox

yea, those switch boxes are expensive.

If it runs and looks good, I would tell your friend - or better yet show him - about the broken switchbox and rather than just to return it, try to knock off ~$200. I'n not saying this to convince you to try to cheat your friend, to me it is a valid point. THe thing has to be replaced whether it's you or him. I wouldn't mess with "fixing" it personally, I'd buy a new one, but only if the price of the motor is right, considering the cost of that part.

 

[saltair]

Re: merc 7.5 melted switchbox

Already told him I'm keeping it. Only paid 450 for boat motor trailer and trolling motor. I'm going to fill the switch and run it until it dies. The boat is small enough I can row it if i have to. Took it out as is today ran it for about an hour. switch box didn't seem to get hot or anything. Ran fine.

Thanks for the help. If anyone knows more about this filling and the purpose for it, I'd like to hear.