1978 Merc 700 (70HP) - Crack/hole in cylinder head. Fixable?

[willvincent]

The title pretty well says it all.

We picked up a boat memorial day weekend, have had it on the water once, at which time I noticed the tell-tale stopped pissing out water. It would occasionally send some steam through the line, and I was able to feel puffs of air. I ordered a water pump repair kit and swapped the out yesterday, the previous impeller was definitely shot, missing one vane completely and another kind of chewed up. After swapping in the new part I put it in a tank to fire it up. Very hard to start, but eventually got it running. Then I noticed it was shooting water out around the spark plugs, not just a little bit, but large gushes with each pump of the cylinder. Primarily on the top cylinder.

My first thought was that the gasket was probably shot, so I pulled the cover and discovered this:

I found the missing piece at the bottom of the water jacket area, this had obviously been 'repaired' at some point.. JBweld? braised? Not sure, but definitely not stock...

Could I repair this with JB weld? or is it basically (as I'm fearing) a lost cause?

Also, assuming it cannot be repaired, I have a line on a replacement outboard, a '64 Johnson 75HP.. I suspect the mounting hole pattern is probably different to my '78 merc, yes? That'd be my luck. Starting to really regret this purchase, just like every other boat or PWC I've ever had, it's quickly becoming huge money suck.

 

[flyingscott]

lost cause that is on the combustion chamber no way to repair that and make it reliable. The 64 75 hp Johnson is not viable if you don't want it to be a money suck. Look for a good powerhead for your motor or one of the 3 cylinder 70 hp Omc motors are an excellent option. They can be reasonably priced and cheap to fix.

 

[willvincent]

What, in your mind, is 'reasonably priced' ?

 

[flyingscott]

500-1000 any less than that is usually a money suck

 

[racerone]

Very common issue with the upper cylinder on those 3 cylinder motors.----Have seen a number of repair attempts.----None successfull.----Replace the block or find another motor.

 

[Faztbullet]

Looks like someone tried to fix it with one of them aluminum repair rods and propane torch........the block is FUBAR.

 

[jimmbo]

Put some Jam on it, that engine is toast. As mentioned earlier, a 3 cylinder OMC engine would an excellent choice but there will be drilling of the transom to make it work. A another Merc, prior to the 1980s would resolve the need to redrill.

 

[willvincent]

Thanks everybody.. pretty slim pickings around here these days... either not much of anything available for sale, or on another boat (which I don't need), or massively overpriced. So I went ahead and picked up the '64 johnson I mentioned in my first post. Haven't fired it up yet, been poking through the rats nest of wires and whatnot determining what other parts and such I may need to acquire. Not much so far. The guy did a terrible job pulling it out of his boat though, lots of cut wires that could have just been disconnected and such.

Gonna fill the old holes with the self-mixing epoxy caulk-gun thing from west marine in the morning and see about getting this thing mounted. Throttle cable end is kind of jacked up so I have to wait on a replacement part to get that going, but maybe, hopefully, with a little luck I can at least get it in a bucket of water a fired up before the end of the weekend. Would have much preferred to be on the lake since it's supposed to be gorgeous tomorrow, but I guess this way I'm forced to take my time and not rush through it and screw anything up .. and I guess we can go fish from shore or something tomorrow.