1975 Johnson 70 HP Water in lower cylinder

[nb_hall]

I was getting water into the lower cylinder of my 1975 70 HP Johnson. Local boat mechanic replaced head gasket and inspected for cracks. Found no defects with old head gasket and no cracks. However told me there was nothing more to check and of I was still getting water in the lower cylinder after head gasket was replaced I would need to start looking for another motor because he stated it wouldn't be worth putting more money into it. Is this my last option or is there anything else I can do since he is not willing to.

 

[Solittle]

Re: 1975 Johnson 70 HP Water in lower cylinder

Yep - Take the head off and check to see if it is warped. Did the engine get hot?

 

[WillyBWright]

Re: 1975 Johnson 70 HP Water in lower cylinder

It's also could be the inner exhaust cover gasket. Go to www.johnson.com and do some clicking til you come to parts diagrams, then navigate to your motor. They'll ask for your e-mail. You don't have to give it. You'll need all three of the exhaust gaskets and possibly the baffle plate. Plus a hammer and chisel to get the old gaskets off (slight exaggeration). Be careful. It's just aluminum. You might even be able to get the gaskets from here at iboats. Look way over on the right side of this page. The baffle plate would be a dealer item if you can still get one.

 

[nb_hall]

Re: 1975 Johnson 70 HP Water in lower cylinder

No it never got hot and the head was checked thoroughly and appeared to be perfect. What about the exhaust gaskets on the port side of the motor could any of those cause this problem.

 

[WillyBWright]

Re: 1975 Johnson 70 HP Water in lower cylinder

Absolutely.

( Great minds think alike. )

 

[nb_hall]

Re: 1975 Johnson 70 HP Water in lower cylinder

Are those reatively cheap to replace and something I could take on.

 

[WillyBWright]

Re: 1975 Johnson 70 HP Water in lower cylinder

Have a look at the lower bolts. Can you get at them? You need to back them off 3/4" or so and the threads should disengage the block. That and scraping off the old gaskets can make it a minor nightmare. Otherwise it's just metal and gaskets.

 

[F_R]

Re: 1975 Johnson 70 HP Water in lower cylinder

If the motor was even slightly overheated, it will warp the baffle plate and make it leak. It doesn't require getting stinking hot. Just something like running in heavy weeds will do it. And water leaking into the cylinders will destroy the powerhead, You gotta fix it.

Also, get a new mechanic if he doesn't know about exhaust cover leaks.

 

[R.Johnson]

Re: 1975 Johnson 70 HP Water in lower cylinder

On the 1975 engine, you will need to remove the powerhead to get at the lower exhaust cover bolts. Use OMC, or BRP seal & gasket remover on the old gasket's first. Then use a 1/2" wood chisel, sharpened, and honed to cut away the remainder of the gasket. You have much more control with a sharp chisel than you do with a flat face scraper on those aluminum face piece's.

 

[nb_hall]

Re: 1975 Johnson 70 HP Water in lower cylinder

Well removing the powerhead is a little more costly and probably why my mech wasn't willing to continue. I thought of creating a removeable panel in order to allow access to those bolts. Does anyone think this would cause any problems, because it appears to me that part of the shield only blocks water from splashing into the air intake.

 

[R.Johnson]

Re: 1975 Johnson 70 HP Water in lower cylinder

If you mean cutting into the lower shroud to remove the exhaust cover, Consider an engine that age from going worth very little to nothing. Lifting the powerhead on that engine is no big deal. Ask what the flat rate is on that job.

 

[00ferret]

Re: 1975 Johnson 70 HP Water in lower cylinder

I am having a similiar problem and have eliminated any problem with the cylinders being cracked however I know my water pump is not working. The head gasket looks ok but does have some wear where the screws were over tightened. Could this cause the leak? I am a college student so I do not have enough money to put into parts without having a good idea it will fix the problem. Once the cylinders are drained out the motor will run fine with ear muffs but not when it is put in the lake. Should I buy a new motor or is this one fixable? Is there any pictures online that can help?

 

[nb_hall]

Re: 1975 Johnson 70 HP Water in lower cylinder

oldd mechanic went out of business, got new one, he found the crack, i sold the motor to him for parts.