Merc 650 from '73 update

[jbjennings]

well guys,
I posted a pic of this "little problem" previously and decided I'd try the trusty JB-weld underwater stuff. The kind you knead together. I also bit the bullet and cleaned the carbs. Taking them off wasn't as bad as I thought. The float was stuck on the bottom carb and the float bowls had about a 1/2 inch of jelly/crud in the bottom of both. It's running great now on the muffs on all 3 cylinders and no water is showing up on the bottom spark plug so it appears she's fixed for a while at least. Anyone else had any experience fixing water jacket holes with this stuff?? Any predictions on how long it will last?
Here's a pic of my problem. It was cracked all the way up to the top cylinder jacket! Water freezing in there???
Any ideas,
JBJ

 

[woody66912]

Re: Merc 650 from '73 update

that engine got very hot at one time my warranty is 5/50 5feet or 50 sec it may be time to give up the dream.

 

[jbjennings]

Re: Merc 650 from '73 update

Ha ha!, You're probably right, Woodie! It does have great compression, though. I really think that if I could get the jacket permanently sealed it would last a long time. I'll post back in a week or so and tell how many tanks of gas it's gone through, or how many ounces, anyway.
I thought it was worth a shot before I junked it. I don't seem to be having any luck finding a good used powerhead. Probably because the 3-cylinder 65's weren't known for lasting a long time, or so I hear.

I'm thinking of rigging up a spare small outboard on it for backup.
Later,
JBJ

BTW, So you think HEAT caused the crack in the water jacket?? Or is it the scuffing on the pistons you're looking at. They actually don't look that bad in person. I didn't know heat would crack the water jacket like that.

 

[emckelvy]

Re: Merc 650 from '73 update

Yes, it's most likely the block was cracked by heat. Although usually when these overheat from loss of an impeller or other cooling issues, the top of #1 cylinder (under the water jacket cover over the back of the block) will crack.

Outboards are always running under a high load (not like a car that can coast part of the time!) and they take very little time to go Thermonuclear when their cooling systems are compromised.

I recall one Forth of Jul about 25 years ago when I was skiing behind my old 14' Fiberform runabout with '64 100HP Merc. Just took off from the ramp and got up on one ski when this huge cloud of steam comes out the back of the motor, and it goes RRRRRRRrrrrrrrrrrrrUmphh!!! That was about it, siezed up tight, when we got out of the water I pulled the intake cover and a number of pistons were pretty fried! Luckily that block had enough mass to absorb the thermal shock without cracking. Unlike your Teeny Weeny 65HP block!

The driveshaft on the 100HP had eroded away just enough around the impeller area that the impeller key spun around in the impeller's bronze bushing until it was worn out, then no more water pumping. A Most Inconvenient time to do that!

A week of wrenching 'til Midnite, a few used pistons, a spare lower unit, new impeller, and we were skiing at the lake again the next weekend! They don't make 'em like that any more!!!

Well, G'luck with the motor, hope she holds together. If it starts sucking up water again, be sure you "oil up" the innards so they don't rust away. You never know, you might find a useable block and be able to fix it proper someday!

Enjoy...........ed

 

[woody66912]

Re: Merc 650 from '73 update

well i didn't want to sound like butt hole. but i just had a 1996 40 hp the same day you posted at work .that didn't melt the cyl wall but it did melt the baffle plate down between #4 #3.i really hope it works.those old mercs were tough.by the way great looking lab got a black my self.best buddy i ever had.oh yeh he was free.