1976 70HP Johnson, water getting in lower cylinder

[Will Bark]

A friend of mine has the above described new to him engine; model #70EL76D serial # 54531863 which is getting water in the lower cylinder. The engine is in really good condition considering it's age. The problem first appeared when he hooked it up on muffs and cut the water on full force from his water well pump which apparently forced water into the cylinder. We drained the water out did a compression test and got 125psi on all cylinders. Cranked it up and let it run for over 30 minutes to dry it out. He used it for at least 3 times and had no problems at all. Called me yesterday and was
going to run it in a barrel when it wouldn't start or even turn over. Took the plug out and found water in it again. Came to my house and I made sure no water left in cylinders; Compression is now 125psi on #1 & 2 and 175psi on #3. What is this telling me? Does this indicate a blown head gasket which is letting water in or is it more likely the exhaust manifold gaskets? The original PO told him that the engine had never overheated and there is no sign of overheat. Any and advice is appreciated. Thanks

 

[ajgraz]

Re: 1976 70HP Johnson, water getting in lower cylinder

Four places I know of for water to get into cylinders:
1) Head gasket
2) Exhaust baffle gasket (or baffle plate corroded through)
3) Oil seal(s) at bottom of crank
4) Crack somewhere in the block

 

[Daviet]

Re: 1976 70HP Johnson, water getting in lower cylinder

I would start with the easiest first, pull the head and check the condition of the head gasket.

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Thanks, will do and report back. Hopefully with that odd high reading that will be it.

 

[F_R]

Re: 1976 70HP Johnson, water getting in lower cylinder

Those engines are notorious for the inner exhaust cover plate warping around the exhaust ports areas. It will happen with just the slightest hint of overheating, or no overheating at all. When it does, the gasket leaks and squirts water into the exhaust ports. In theory, you could have the plate milled flat, however the original problem stems from it being too thin in the first place, and a long span between bolts. Milling it will make it thinner yet.

But by all means, check the head gasket first, simply because it is the easiest. You most likely will then be going on to the exhaust cover next.

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Owner wants to go ahead and replace the head gasket as well as the exhaust manifold gaskets. After studying the diagrams I think we need to order for the exhaust gaskets one #331917 and two #331916; could someone confirm that this is correct for this engine?The head gasket part # is not a problem. Thanks for the help

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Can anyone verify the part #'s for the gaskets listed in post #6 before the owner orders them this afternoon. Thanks

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

another way to solve this problem make a carbon graphite manifold plate from 10mm like this 1 i made then you get 2 advantages it reduces the heat & doesnt warp , the original ones made are 10mm thick & in some places 6mm thikck the way its casted & that is around the exhaust ports

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

another way to solve this problem make a carbon graphite manifold plate from 10mm like this 1 i made then you get 2 advantages it reduces the heat & doesnt warp , the original ones made are 10mm thick & in some places 6mm thikck the way its casted & that is around the exhaust ports , on my one you will see 2 extra holes by the centre port the factory never made this provision so i casted my own bolting holes

you want part no, for gaskets
0317227 ,0317228 ,0319097

manifold plate ,0317215

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Durban, thanks for the reply relative to the gaskets. Also, thanks for the concept of fabricating a new plate out of carbon graphite; however, where would one source the material and our problem would be to find someone who could come up with the finished product.
Seems to me that would take someone with the abilities of a machinist such as yourself. I don't know if our small town even has someone with those abilities if we could find the material. Seems to me if the OMC engineers could use a little forethought these type of problems wouldn't occur in the first place.

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

you could also use 10mm aluminum i used graphite for my radiator conversion & have omitted certain holes for the water to flow the way my design goes , but 10mm alumiunium would work ,

something for you to read
http://forums.iboats.com/showthread.php?t=528873

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Now know it is the exhaust manifold; gaskets are ordered but have not gotten it off the engine to see what else has to be done. Are these baffels still available if needed or will have to search salvage yards? Would try durban's method if we can locate a machinest. Thanks for any help and advice.

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

if you gonna use 10mm aluminum you need to make your own gasket , the 1 that fits on top of the manifold from 3mm novus gasket sheeting , because the original 1 is cast in such away for water to flow , now 10mm aluminum will be flat so you need to increase the thickness of the gasket for water to flow , k cheers

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

We still have the head off and notice that there are no water deflectors installed in the water passages around the cylinders; should there be or does this engine not use them? If it is supposed to have them does anyone have a diagram of where they should be located? Thanks for any info.

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

70 hp don't come with deflectors not as far as i know only v 4,s

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

not only the manifold plate warps its also the exhaust box as well check the curved casting the one in the center it normally lifts about o.5 mm right there where the bolt goes through in the center of the box k check it out with a stainless steel rule this one in the photo has been fixed with water based course grinding paste & a thick glass top on both sides

 

[durban]

Re: 1976 70HP Johnson, water getting in lower cylinder

tomorrow i will also show you where else these motors warp you have to be careful otherwise the water will just come back in i have found a number of blocks so far with this problem where the actual block has warped too , but don't worry too much its easy to fix it cheap , cheap

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Thanks for the reply, will be sure to check each of these areas.

 

[Will Bark]

Re: 1976 70HP Johnson, water getting in lower cylinder

Hopefully the saga has ended; owner found a machinest who checked each part for warpage and found none. We then checked the engine block with steel straight edge and found no warpage there. OMC mechanic also checked each piece and advised to use the new gaskets and reinstall. Put everything back together and torqued the bolts on head and manifold to specs. Cranked the engine and ran it up to operating temp in barrel. Let the engine completly cool down and retorqued the bolts. Started and ran engine again up to operating temp. Checked the cylinders for and H2O intrusion and found none. Compression 120 across the board. Again. hopefully this bad boy is ready for several more years of service. Thanks to all who responded; this is a great forum.