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Mercruiser exhaust riserelbow

kedwards

New member
The riser off of the manifold

The riser off of the manifold had rotted so I bought a new one. The one I replaced had a gasket to the manifold then a thin metal plate that blocked off the 3 slots and then another gasket to the riser. The new riser came with just 1 gasket. I asked the dealer if I needed to buy another gasket in order to sandwich this metal plate that blocks the slots and he told me that I didn't need the metal plate since I didn't need to block off these slots. This makes me nervous. Can anyone verify if I need this plate?
 
This motor is a 1980 Mercruise

This motor is a 1980 Mercruiser Model 170 inline 4 cylinder that is fresh water cooled.

Thanks for your interest Bill K
 
"Find another dealer... I don&

"Find another dealer... I don't know about that particular motor, however there are two varities of FWC systems, full and partial. The partial ones run raw water thru the manifolds and risers, the full systems run fresh water in the manifolds and raw water in the risers. The purpose of that blocking plate is to isolate the two cooling systems, i.e., keep fresh water in the manifolds and prevent it from dumping out the risers. You should see a seperate raw water feed to the riser on your system."
 
"You are using what I consider

"You are using what I consider the wrong terminology........

Closed cooling or fresh/raw water. There is no other description in my opinion. Any other description just makes it confusing.

Closed cooling uses a heat exchanger and a 50/50 water antifreeze mix so the risers/elbows use a block off plate to keep the antifreeze in the motor, maifold, thru the heat exchanger.

The only fresh water flows thru the voltage regulator and thru the heat exhanger then thru part of the manifold and out the riser/elbow to keep the exhaust cool..

A fresh/raw water system takes the fresh water and circulates it thru everything and there is NO heat exchanger or antifreeze or block off plates expect for the old log style manifolds.

OK are we clear on this or is there need for a better explanation........???

So Ken please revise your info and tell us exactly what you have. Allthough a 170 is the merc 4 cyl motor with the CLOSED COOLING system.

So of this is so you need the block off plate to keep the antifreeze in the motor.

Here is a parts picture I believe is of your system. ITEM 31.






218866.jpg
"
 
Thank you everyone for the adv

Thank you everyone for the advise. You have saved me a lot of time and certainly my engine!-- Ken
 
Re: "The only fresh water

Re: "The only fresh water flows thru the voltage regulator and thru the heat exhanger then thru part of the manifold and out the riser/elbow to keep the exhaust cool.. "

Not if your boat is sitting in salt water :) LOL
 
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