Mercury 500 water jacket leak... fix?

[ashedd]

I replaced the impeller in one of my '66 500's and now I get water from the #1 spark plug. All research points to water jacket gasket failure. As I understand it, you are required to remove bolts that usually break to replace the gasket, and perhaps even remove the power head. Breaking bolts and/or removing the power head is not something I'm wanting to do this season(These motors are new to me). I've read about people putting RTV on the gasket by the plug hole and that stopped the leak. Is this something that can be done? There is no indication of water getting into the cylinder that I can tell. Water just drips from the top plug when running. Normally I wouldn't care too much but it gets the other plugs wet. I'm prepared to replace the gasket in the winter if it comes to that.

Also it's not peeing from the tell tail, I'm going to clean all that out and see if that helps, could a blockage cause higher water pressure? Perhaps a higher pressure would allow the leak to be more pronounced?

Thanks

 

[jimmbo]

The motor ran a little hot at one time. The water jacket cover warps a tiny bit. You can change the gasket many times, the leak will almost always return. The gasket works best if applied dry. I've seen a silicone bead feathered where the cover meets the head in the spark plug recess. It looks ugly so use a silver RTV. In 66 the blocks were silver

 

[ashedd]

Do the bolts need re torqued over time? I read that someplace too. If RTV will work I'll use it. I guess the leak is a pretty good sign that the new impeller is pumping. The heads on either motor(I have twin 500's) never got hot at all, pretty much stayed cool to the touch. I ran them each about 6-7 mins at high idle when on the muffs, so I guess that's a good sign.

 

[GA_Boater]

How bad is the leak? A steady drip, slow drip or a stream? Has the motor been used in salt or fresh water?

Water can't get into the cylinder with the leaky cover. If the silicone stops the leak, you can put off a fix until winter or let it drip until then. Just keep an eye on it

 

[ashedd]

How bad is the leak? A steady drip, slow drip or a stream? Has the motor been used in salt or fresh water?

Water can't get into the cylinder with the leaky cover. If the silicone stops the leak, you can put off a fix until winter or let it drip until then. Just keep an eye on it

somewhere between a slow and steady drip.
Right now I'm trying to figure out the situation of my new starter not having the screw holes to mount the solenoid.. That and it took awhile to get the motor started, but I suspect air in the fuel line. So much for having this boat in the water this week.

 

[GA_Boater]

somewhere between a slow and steady drip.
Right now I'm trying to figure out the situation of my new starter not having the screw holes to mount the solenoid.. That and it took awhile to get the motor started, but I suspect air in the fuel line. So much for having this boat in the water this week.

Had the same problem with a replacement starter. I used two screw type hose clamps end to end to mount the solenoid bracket and extended the ground wire to the battery ground connection on the starter. Orient the solenoid so it clears the cowling.

Pump the bulb until it's good and hard. You could take the motor end twist connector off and pump the bulb into a container. Depress the ball a little and watch for splashing. If the hose has a removable clamp on the twisty, stick the end of the hose in a container.

 

[racerone]

????----On the older motors the bolts are fine threads with a nut.-------Should be an easy fix to replace the gasket !----No need to remove the powerhead .

 

[ashedd]

My starter rebuild guy suggested hose clamps too. I'll use clamps for now, having him rebuild the old starter as a spare or something. Funny thing is that the other motir has the original starter with 1965 stamped on it.

Primer bulb never gets hard, so there's a leak somewhere.

I'll look closer at the bolts, but I'm concerned about the cover being warped like someone else mentioned.

 

[ashedd]

Also noticed the other motor has a different flywheel and no stator/alternator. Maybe I can piece together the parts needed to add the alternator, if it's even worth it. I dunno yet.