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1972 Johnson 4hp running hot

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abl1111

Regular Contributor
My 1972, 4 hp Johnson that starts easily seems to be running hot and stalling. Gas/oil mix is right, ran fine early spring, not used with any frequency, water coming from exhaust feels fine but do not know condition of water pump impeller ( can't remember but I think I replaced it recently - but cylinder head gets HOT, boils water with ease, and smokes. Then stalls out.

What should I focus on ? My thoughts are:

water pump but I doubt it
piston / cylinder wear
running lean

Thx - I know it's an oldie but I've never had this problem before...
 
OK,

I'll check the impeller 1st. I think I replaced the impeller less than 1-2 hours use ago. I'll ck it though. Assuming that's Ok, remove the head next ?
 
Yes it will accelerate but I do not do that when it's hooked up to freshwater 'ears' ( no resistance on prop ) or in a garbage pail - but she would rev fine. But the head could NOT be touched... It was hot. I put a few drops of water on the head and it sizzled in seconds...

When I did use the 'ears', water was flowing freely out of the main exhaust and spurting in a mist from the '8-10 holes'.

She owes me nothing but I think if its something minor, I'd like to fix it. It's used hardly ever as it's a back up for my small daysailor if the wind quits. Used it 3 months ago for 20 minutes no problem. Then, not until the other day when I was going to start her and winterize her.
 
If you replaced the impeller a few years back then pull the head off and take a look at the water jacket passages...you may find blockages.
 
I don't think there is a way to backflush this motor, but if there is a port in the water jacket or if it has a thermostat try to run a hose through that with the lower unit removed and see if water flows out the water tube. Other common issues are a bad or lost impeller key which allows the impeller to not turn while the engine is running. A bad water tube connection to the water pump. Debris in the water jacket, blocking the flow thru the powerhead evenly. When you replaced the last impeller was it in one piece or were pieces missing? I recently replaced an impeller that all the fins were missing and later found almost all of them up inside the water jacket blocking essential passages.
 
I've done it both ways with the 'ears' and a garbage pail of water - usually with the ears. Usually winterize it that way. There is an intake for the ears to be placed. Never had a problem.

Compression before a problem was top cylinder 85, bottom 75. Haven't checked recently but I will.

I don't remember about the old impeller - but pretty sure I replaced it.

If water is coming out of the exhaust well, that would prove that the impeller is working - is that correct ?

I will pull the lower unit and run water directly if possible ( I did this with yamaha 9.9 - 2 stroke to confirm it was cooling well - this Yamaha had to be in a pail - no water intake )

So, first thing I will do is a compression then remove lower unit and try to run water directly into powerhead. - sound like a plan ?
 
OK, Some more info. I did compression - 75 lbs each cylinder.

Plugs both look new.

Pulled head off and the cylinders look great - all smooth. I'm very happy with the compression and the look of the cylinder and the head. I can't see any obvious leaks. The gasket was FIRMLY attached to the head. I carefully scraped old gasket off and will replace with a new one. The exhaust cover... hmmm , haven't pulled that off yet - should I still do that too ? I have not seen the rings but assume they are OK from the nice, uniform cylinders.

1) what adhesive gets put between the gasket and head and gasket and block ?
2) should I use permatex anti seize on the bolts when re-attaching head ?
3) I don't have a torque wrench - can I gues'timate ? If not, I can borrow one.

Before I put the head on, is there a way to test water flow to the head ?

And, can you tell me this -

If water is flowing well out the exhaust, is this telling me that the impeller is functioning ?

Is it possible for the impeller to be functioning, cooling water comes out the exhaust but NOT be cooling the cylinder head ?

Thanks for all your help.

BTW - the head gasket looks like the first pix you put up: http://www.ebay.com/itm/Sierra-Johns...ec4aeb&vxp=mtr
 
Often gaskets can be re-used.-----In this case that gasket will likely tear.-----Cheap enuff or easy to make that one.
 
Ok. Pulled the exhaust plate. (1) bolt snapped in block with 2 threads to grab onto ! The bolt is an 'inside one' - there are a total of two inside ones.

All looks great in there in exhaust area. Gasket is SHOT! Aluminum exhaust plate looks a little pitted where the water flows.

Questions:

- The bolt that snapped - is a bolt that looks like I could get away without - but, I'd like to try to remove it - any ideas ? Its soaking in PB Blaster now.
- The exhaust gasket - it looks pretty custom - can I buy a new one, or, if I make one, what material would I use - a high temp gasket maker ?
- The exhaust plate - pitted where gasket fits - hoping that the pressure of the plate tightened down will compensate

Is there anything else I should do while this is all apart ? Once I put all back together again, I'll be at square one, cause all 'looks OK'.
 
The gasket is available from this site and listed at $2.16------Not sure if you could make it for less than that , unless you had a piece of suitable material on your work bench.
 
Pix on left is of the snapped bolt - top left. Right pix shows the corrosion along where the salt water passage is to cool the exhaust 'chamber'.
Bolt - I'm going to give it s shot removing it. Corrosion - I'm going to sand with the 200 grit a bit. Wish there was a high temp epoxy to fill small crevices with...

photo 1.jpgphoto 2.jpg
 
OK !!! That bolt is @##$#$% 'ed !!!!

Almost had a great hole to re-tap - was on my 3rd consecutive drill bit, drilling larger and larger hole - and the bit snapped, flush in hole. Lights out.

I do believe that the neighboring bolts will hold it all in place with no leaks ( at least that's the theory I'm going with now - 'cause I haven't got any options ! :) ).

As for the plate, I'd like to buy a replacement, but don't know if it's available and don't want to waste $$$ if part will work.

So, the Perfect Seal, or the Permatex seal; they're used in conjunction with a gasket and help make a nice seal - correct ?

I do wish I could make my own 'thicker' gasket to compensate for the corroded plate - something that would fill in any potential voids - is there something like that ?
 
something that would fill in any potential voids - is there something like that ?
Click to expand...
Perfect Seal, or the Permatex seal will work; just be sure to clean the plate thoroughly. A 1 hour dip in vinegar will remove the mineral deposits and not hurt the aluminum.
 
The plate is available, on this site about $20 ---Myself I would take one of a donor motor or make a stainless one.-----Big red letters at top of the page for the parts lists and prices.
 
OK

All put back together again. Pulled lower unit and went to bypass the impeller - for now.. Bought a bunch of short pcs of different diameter hose that I combined to be able to go from the garden hose to the brass / bronze pick-up tube that would normally attach to the impeller housing.

I would think that once this gizmo was in place - motor off- and I turned the water on that the water would just flow through the circulating / cooling system. Not the case. When water pressure was put on, the hose from too much pressure popped off.

The motor started immediately. :)

But, I turned it off right away to avoid overheating.

Should the water just flow ? If yes, then there is a blockage somewhere.

Even when the motor was running, no real water was spritz'ing out the small holes.

The cylinder and exhaust cooling passage ways were clean - what do I do now ?
 
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If all were right, would the water flow right through the system ?

What the h*ll could possibly be in there ? Seems like the water had to go through the strainer on the lower unit...

Pulling the power head sounds like a PITA !
 
Update - straightened a wire hanger and put it up pickup tube - clear it out - water flows great.

Unfortunately, that bolt that snapped for the exhaust cover is allowing water to piss out in that area.

Frustrating !

Now that broken bolt/ drill bit has to be removed and tapped or I think I'm 'screwed'. Any idea how this can get done with maximum chance for success ?
 
Can you cut a slot in the drill bit w/a Dremel/cutoff blade and back it out w/a slotted (flat blade) screwdriver?
 
He's already said that he broke a drill off in the bolt. Unless he can get that out first, he's not going to be drilling anything.
 
Maybe use longer bolts and a " strong back "--to put pressure on the plate and forget about fixing the bolt / drill that is broken.
 
Such a be'atch ! I thought about the strong back idea - to assure that the plate stays FLAT ! Going to see if a machine shop can do anything. If not, then I'll go for fortifying the area with a 'strap'.
 
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