75 Johnson 40 hp found water on spark plug

Bought this boat not too long ago and it idles a little rough. Also when try to go full throttle it surges until it finally runs wide open. Guy that I bought it from said the motor had been gone through a couple years ago. All carb gaskets look pretty new. So I pulled the carb all apart and made sure float was adjusted properly blew out with air and reassembled everything. Changed old spark plugs and noticed one had some water on it when I pulled them after running it for the first time since changing them. I pulled the plate off where the spark plugs screw into and the gasket is in ok shape but wasn’t sure where water would be getting in. Noticed that there was some water between plate and gasket. Any help would be greatly appreciated. Thanks

Olaf

Two main causes of water in cylinders are the head gasket and the exhaust cover on the side of the powerhead. Only way to track it down is remove the suspected parts and look.

BTW, water in the cylinders, if left there, will destroy the powerhead bearings.

The cylinder head has a water jacket cover.----And yes you would find water in there.

Thanks both of you for getting back to me pretty fast! If that exhaust cover has a bad gasket and is leaking would that be the reason for the surging at full throttle too? And I’ll check and see if there is any water sitting in there.

Yes. But not the only possible reason. Hey, spray water in a fire and it doesn't burn, right?

Yeah good point, I’m going to take that cover off and see what shape the gasket is in, I’ll let you know what I find, thanks again. And I’ll get the water out if there too if there’s water sitting in there

When a motor start it fills up with water.-----When it stops water all or most all of it drains out of the block.

Should I still pull the cylinder head off? And I found that where the outer exhaust cover is the bolts along the bottom have worked their way out so trying to get to them to tighten them up

Try a compression test before pulling head,Does not cost anything

Where would I get that done at? A boat place or just any auto parts store?

An auto parts store will loan you one if a deposit is put down