1980 150 Black Max leaking head gasket? (photos)

NWChris

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Hi, I have been experiencing missing when motor is cold and on low RPM's. Spark plugs show milky grey liquid (water). No water in fuel, so I pulled a head just now and attached pics. I have a new head gasket to install, I just wanted to confirm with more experienced folks that this is the correct move.
-Chris
 

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NWChris

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Well, I cleaned the mating surfaces as best I could. I scraped carefully with a razor blade, then finished with a little nylon brush on a dremel. Installed the new head gasket, torqued to 30 ft-lbs in the proper pattern going 10 ft-lbs at a time. I oiled the head bolt threads with 30 weight oil. The bolts seemed in good shape (fresh water boat). A few little external leaks that had developed over the years now disappeared, but the plugs still came out grey/ milky. Cylinder bores looked good (to me). My compression actually got a but worse, it was about 135 psi before the job, about 120 to 125 after. The other bank (starboard side) is also showing milky plugs, but I have not touched this side. It's compression is about 140 to 130.

I noticed in the photos that the grey stuff was on the exhaust port side on the cylinder head. I read somewhere that water can come in from a blown exhaust cover gasket? Could this be the problem, or are my heads possibly warped? I did have the high temperature alarm go off briefly last summer, so I installed a new impeller this spring.The old one was stiff, but not broken.

I've also noticed water occasionally squirting out the poppet valve hole on the starboard side of the motor. I opened it up, cleaned the spring and diaphragm. No holes, it looked in good shape.

Any suggestions welcome.
Thanks,
-Chris
 

racerone

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I have never seen an outboard head that was NOT warped after 20 years of use cycling from cold to hot.-----But you should also replace the exhaust cover gaskets yesterday.
 

NWChris

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Thanks for the info. If it doesn't rain today I'll remove the exhaust cover. Yes, this motor has seen temperature extremes. I've retired to a small island two miles out on Lake of the woods, Ontario. I've driven this boat through hot summer days, to October snow storms, to breaking spring ice. After 37 years of use it doesn't owe me a dime, it's just hard to let an old friend go...
-Chris
 

racerone

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Every head I look at from 6 hp to 200 hp has been warped to some degree.----Ten year old motors or 50 year old motors.----Use glass plate and lapping compound to true them up at little expense.
 

racerone

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V-6 heads on Mercs and OMC motors all warp.----------The head on an inline 6 cylinder does not warp.-----At least I have never seen a warped one on an inline 6, Yuk, yuk.
 

NWChris

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It appears to be all 6 cylinders. At first I noticed it mostly on one side, but now I see grey milky oil on all six plugs. slightly more on the lower ones. I am guessing this would point towards a blown exhaust cover gasket? We have had 8 inches of snow, so the project was on hold. But I'm now applying penetrating oil (acetone and ATF fluid) and slowly trying to get the inner exhaust plate off. I've broken one bolt that I will try to get out when the plate is off. I have gaskets on order and will report my progress as things develop (or go horribly wrong).
-Chris
 

NWChris

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I now have the inner exhaust plate about 1/32 to 1/16 inch away from the block, but cannot get it off. I will keep applying heat and penetrating oil, but as if its bolted from the inside. The outer exhaust plate came off no problem, it's the same bolts for both?
-Chris
 

NWChris

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Thanks Dukedog. I just can't figure why the inner plate won't come off. I have it ti the point where I can slip a slotted screwdriver between the plate and the block and wiggle it a bit. It wiggles all the way around. I have picked and oiled away the rust around the one bolt that broke, and it has movement too, so I don't think it's holding up the show. You can see it in the upper starboard side. I have put 6 wooden wedges (clothes pins) around the plate to maintain a constant release pressure, but not too much pressure (I hope). I suspect the divider plate is glued to the block with carbon. so I have tilted up the motor and squirted in penetrating oil, hoping it will find its way to the divider.

Any ideas on how to release this inner divider plate would be much appreciated!!!
-Chris
 

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Dukedog

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just rust and carbon build up.. use tha wood wedges around tha whole thing... it won't "scar" up tha flat surfaces... tha main spots are center top and bottom where there are "slots" in tha block............
 

Faztbullet

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Should slide right out with a little persuasion, be careful as that's a GEN 1 block and plate may be hard to find.
 

NWChris

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Thanks again, you guys are very helpful.
Well, gentle heat and lots of oil, and no luck at all removing the divider plate. This thing's really stuck.

Could I remove the port head again (that's the side that wiggles less) and spray Liquid Wrench into the exhaust ports to loosen the divider plate?
Could I then reuse the new head gasket?
-Chris
 

NWChris

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Well, I've removed the head on the port side, and curved the red straw on my Liquid Wrench so that it sprays a bit aft when I spray into the open exhaust port.I've rotated the flywheel to do all three port cylinders. But the darn exhaust divider plate is still stuck. I will leave it sit over night and try some gentle tapping (using a dead blow hammer) and prying tomorrow. I've applied some gentle heat as well.

Does the exhaust port lead directly to the divider plate?
Is there a better way to loosen this part?

Thanks,
-Chris
 

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NWChris

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I finally got it out!! Good thing I'm retired with lots of time.
It seems it was stuck in one area, kind of burned. My impeller was pretty old last year. hopefully no permanent damage done?
Three questions:
1 What do you call the squiggly silicone thing in the groove?
2 Does a Merc dealer supply it?
3 Do need some kind of gasket goo for the exhaust plate gaskets in the picture?

Thanks,
-Chris
 

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NWChris

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Well, I've found it's called the exhaust divider plate seal. I will phone my dealer in the morning to see if they have one.
So should I use goo on the gaskets?
And I'll try attaching those pictures again...
-Chris
 

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NWChris

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Hmmm... no bites. I guess I'll try putting the gaskets for the exhaust divider plates on dry.

By the way, one of the bolts holding the plates broke off due to corrosion. I had just the shaft of the bolt sticking out of the block by about 3/8 of an inch, thankfully enough to grab it with one of those tightening channel lock pliers. I finally got it out by using the propane torch and candle wax trick. Amazing!
-Chris
 

Dukedog

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put a tag bit of grease on tha silicone "spaghetti" thingy ta hold it in place in tha grove.. dry, no type sealer.....
 
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