88HP Cooling questions.

[willy16]

Firstly. I want to thank those that have answered questions. I have learned alot scrolling thru these posts. Thank You.
I own a 1989 88Hp Johnson. I have serviced this engine top to bottom & it seems to run well.
My question is this. When i removed the T-Stat cover the old stats were rotted away,some parts missing. So where would these parts windup?? I was running the engine today (i always fret about temps) when i noticed there was exhaust flowing
from only 1 of the ports on the exhaust leg (just below the cowling). Right side open.Left side closed. I do not know the flow
path,so i can't figure this out. Any help? Thank you.

 

[boobie]

Find a factory service manual and this will have a water flow chart in it.

 

[F_R]

I'm fairly sure those two exhaust relief ports are the same. Just a quirk that sometimes it blows water out of only one. At any rate, that is only a tiny portion of the water that is actually going through the system.

 

[Joe Reeves]

In agreement with both of the above replies.

********************
(Exhaust Relief Ports - Exhaust Housing (Inner/Outer)
(J Reeves)

The long housing between the powerhead and the lower unit is called the exhaust housing. There is a inner housing within it that has a heavy duty seal around the bottom of it, or heavy duty seals around a inner extension between the housing and the lower unit.

The red hot exhaust travels down thru that inner tube and out the propeller with a somewhat supply of water to cool the propeller hub. A good amount of water surrounds and fills the space between the outer and inner tube, otherwise the outer housing would get so hot that the paint would burn off.

Some water pumps, for some reason (differing even when new) exert a great amount of water pressure, and if the exhaust housing seals are in perfect condition, the water fills the tube to a point of overflowing.

This brings into play those two holes or slots, whichever the engine might have, at the top rear portion of the exhaust housing just below the powerhead.

Now, if those two holes/slots weren't there, water would continue to flow up into the cylinders. Water not flowing out of those holes is no concern for alarm UNLESS that outer housing suddenly becomes extremely hot..... the warning horn should sound long before that happens.

The main reason for those holes being there (exhaust relief holes) is that when at an idle, there is an extreme amount of resistance encountered by the exhaust trying to escape due the fact that the outlet via the propeller is now blocked by a wall of water. The escape route in this case is for the exhaust to escape out those two holes, otherwise the engine would slow down quite quickly and die. If exhaust cannot escape, air/fuel cannot gain entrance to the engine.

 

[willy16]

Thank you for all the replies,& for explaining the purpose of these relief ports. I will study my manual for more info on the cooling flow. So any thoughts on where the bits of the old stats might have gone? Not sure if bits might just flush thru or
will cause a problem at sometime.I did not find any parts in the lower unit when i had it off.. Thank you.

 

[Chinewalker]

Did it appear that anyone had been in there before? Not uncommon for some well-meaning shade-tree to remove all or part of the thermostat bits to "improve" the system.

 

[Joe Reeves]

In agreement with "Chinewalker."

Also very possible those small nits & pieces blew out the exhaust with the cooling water.

 

[willy16]

Thanks for the replies. late in my response,had to work for awhile... yes there were bits of the old stats still in place.
This poor engine just hadn't been serviced for a long time. I've run this 88hp in a barrel & on the flushing device & the temps appear normal. This was a saltwater engine (Gulf of Mexico) . I do not put my boats in the salt. Guess i'm a river rat....
at heart. Thanks again..