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Johnson 1989 70HP Head Gasket

puretic

puretic

Member
Hi everyone,

I'm about to install a new head gasket on my outboard.

The one I just removed was the type with several small holes in between the bolt holes. The one I removed from my donor/parts motor did not have this.

It seems to be a design flaw to have the holes, as they allow water to come into contact with the flat head surface, and let corrosion sneak in around the gasket. The head was in fairly poor condition, compared to the head on the donor motor.

I just purchased one online and according to the seller, the type with the holes is the only one he has ever sold, but I'm having second thoughts about using it.

Any wisdom appreciated!

Thanks,
Ben
 
Use it.----The head is WARPED so make sure you resurface it before installing it with the NEW gasket that you ordered.
 
Ok, I've received the new gaskets.

I've been doing some final clean up in the jackets and mating surfaces and their is a fair amount of pitting.

In this first image the pitting can be seen on the aluminium around the bore in the top right. The aluminium is worn to the point I can catch my fingernail on the cylinder sleeve if i drag it toward the centre of the bore. There is also a small deflection on the edge of the piston which can be seen in the photo.

Is this suggesting exhaust gases have been getting out, or water has come in at some stage and damaged the piston?

If I go ahead with a clean head and block, and new gasket, will it clamp it shut or is this a complete deal breaker?

Thanks,
Ben

lV3QZjA.jpg
7qYEMHB.jpg
 
That mark on the piston is a concern.----Any good pictures of the cylinder wall area with piston at the bottom ?-----What was your motor doing / not doing before you took the head off ?
 
The mark on the piston is aligned about 2/3 of the way up the the visible intake port. There is no corresponding damage in the bore. The same goes for the other cylinders, and the facing top edge of all 3 cylinder sleeves are flat and without damage.

I purchased the motor second hand. My initial problem was an overheating with what I thought was due to a failed water pump -- no water out of the telltale. I took the lower unit off and it was destroyed. I replaced it and the motor ran well, like it did before the pump failure, but at consistent higher revs it overheated again - constant alarm sounding. I waited a while for it to cool down, and drove it home at a slow but not crawling pace, about 15-20 minutes without issue. This is when I decided to remove the head for inspection. The water jackets were fairly crusty, but not blocked.

e6UJEZu.jpg
 
This photo was taken before I started cleaning the cooling passages. I may have poked around and cleared a little of it.

WrdcKYi.jpg
 
Give it a try, be sure to surface head too. Nice clean up job. Cylinders look okay. How are threads, how did you clean them? If bolts are decent reuse them or I can find you some sweet used ones.... Minnesota fresh water. Tim's Outboard Hackensack MN 218 682 2331, Mike or Dan.
I have successfully sealed up worse than this with a little Loctite 518. It will hold to 300 degrees, filling these questionable imperfections. Avoid getting any on the threads, instead there, use a LITTLE anti seize after poking a LITTLE down in the thread bores. You don't want any to ooze out into the gasket surfaces.
 
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Hi Tim,

Bolts look ok but need dressing up. I think I will soak them then buff them up on a brass wheel. Cleaning the threads I'm not sure about. I was going to try using a tap but apparently that might not be suitable. I have spare bolts so I was considering notching one of them to use as a chaser. I will keep you in mind if I need any spare parts.

I like your idea about the Loctite, I'm going to do it.

Regarding the anti seize, do you think I could use Permashield gasket dressing? It's blue and non setting, maybe similar to Hylomar. I thought it might be good.

https://www.permatex.com/products/g...uel-resistant-gasket-dressing-flange-sealant/
 
Looks like a good product. Have to try it myself. Nickel anti seize the threads for longevity and protection. Careful not to over torque as it will effect readings, there is plenty info on internet covering this subject.
 
I made up a little thread chaser.

PfOToYq.jpg

I lubed up the block threads and spun it in every hole by hand with no resistance, and all the gunk came out nicely.

I was thinking about applying the anti seize to the chaser and running it in and out of each hole to coat the insides thinly and evenly before I go about putting the head gasket on. What do you think?
 
I've not done this before so I'm not sure of the torque specs for the head. I understand to follow the sequence stamped on my head but unsure of the torque values. From the pdf I have, I think it says to tighten to 18-20 ft lbs, does this mean go around at 18 first, then a final pass at 20?

Also, do I need to dress the exhaust gasket before I install it?

Cheers,
Ben
 
Go 6 ft-lbs in first round.-----Then go round at 12 ft-lbs-----Final at 18 ft-lbs.-------Check torque after first cool down.
 
timguy said:
I use a little, depends on the condition of the surfaces. In your case, I probably would.
Click to expand...

I used a little that should help with the imperfections. Is there a suitable lube to ease in the temperature alarm sensor and help it with removal later or does it need to go in dry? I'm trying to push it in now and its stubborn, hardly budges. Don't want to damage it.
 
I just started it up for the first time. Seemed to be idling a little high.

I let it run for a couple of minutes, then pulled the plugs as I wanted to do a compression test.

The top cylinder had a little steam coming out and my heart sank. I did a little more thinking and thought it may be a little unburnt fuel or residual moisture coming through the exhaust or intake ports as maybe that was the only piston in that position.

Any ideas?
 
High idle, i become think that it might be due to leaking gasket in somewhere intake manifold, or leaking gasket between carburettor and intake manifold. What was the condition of your spark plugs after test drive? If there is air-leak somewhere intake system, it can be seen from the plugs, because they are then overheated. Also you can check the operation temperature of your engine. Air leak allow too much air enter the engine, mixture will change too lean, because there is too much air related fuel and then operating temperature will rise too high, so this is very dangerous to engine.
 
I don't thing I have ever seen an intake leak that would cause a motor to overheat.----Are you test running on a hose at home or with the boat floating in the water ?
 
racerone said:
I don't thing I have ever seen an intake leak that would cause a motor to overheat.----Are you test running on a hose at home or with the boat floating in the water ?
Click to expand...

I tested it at home on the muffs. No overheating, I was just curious of the source of the steam like residue in the cylinder.
 
Probably just came back in from the exhaust because that piston was down when you removed the spark plugs. That's all we can hope.
 
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