1978 mercury 90 hp water problem?

[joe2403]

On the back of motor on bottom of block their are two exhaust ports. Is their supposed to be water coming out of these? I have been trying to get this figured out for 2 years now. I also have two manuals that don't say any thing about it. Is this a sign of exhaust plate gaskets leaking? any help would be great!

 

[Moody Blue]

Re: 1978 mercury 90 hp water problem?

Welcome Joe, water out of the exhaust ports is perfectly normal. Those ports are actually exhaust relief ports where exhaust gases and cooling water exit the motor while at idle. The normal exhaust path / cooling water path is thru the prop hub, but there is too much back pressure when the motor is just sitting in the water. Once the boat/motor start traveling thru the water, the exhaust gases are drawn out of the motor thru the prop exhaust port.

 

[joe2403]

Re: 1978 mercury 90 hp water problem?

thanks, that makes alot sense. mechanics that i talked to couldn't even give me a straight answer. Its nice that theirs people like you out their!