340 mercruiser coolant out exhaust

J

jlowers

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Closed (salt water cooled) system, heat exchanger ok. Isolated each side and when coolant is poured into each sides respective hose from the heat exchanger (actually the return coolant line), coolant goes out exhaust purely by gravity.

Replaced one riser and still leaks. I presume that sides manifold is bad and the other sides riser and or manifold is also leaking.

Is there anything I may be missing before we replace both manifolds and riser?

Thank you.
 
Bt Doctur

Bt Doctur

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Re: 340 mercruiser coolant out exhaust

does it cool the manifolds with A/F also? Then you need blockoff plates or blocked off riser gaskets to keep the A/F apart from the salt water leaving the HE
 
J

jlowers

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Re: 340 mercruiser coolant out exhaust

Bt Doctur said:
does it cool the manifolds with A/F also? Then you need blockoff plates or blocked off riser gaskets to keep the A/F apart from the salt water leaving the HE
Click to expand...


Thank you but I'm confused, the engine has been fine for quite a while till now. We thought it was a bad riser so we pulled the starboard riser off and replaced it. The ss gasket had the openings to allow coolant into the riser so we replaced with same. How can that be wrong after running so long with no problems?

Thanks again
 
alldodge

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Re: 340 mercruiser coolant out exhaust

Have a pic's and show which hose your pouring A/F in
 
J

jlowers

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Re: 340 mercruiser coolant out exhaust

AllDodge said:
Have a pic's and show which hose your pouring A/F in
Click to expand...

I'll do that soon.

Every thing I read says I need a stainless steel separation plate which makes sense BUT,

We replaced a riser, it only came with a new slotted stainless plate and the old riser was also slotted. How could we run for a year with a slotted plate if solid was required?

Thx
 
Bt Doctur

Bt Doctur

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Re: 340 mercruiser coolant out exhaust

If your He cools the exaust manifolds and your HE waste water cools the risers you need to block them off.There are no slotted SS plates only solid ones. You can use aany slotted gasket, then the SS block off plate, then another slotted gasket.see page 5
http://www.boatfix.com/merc/Bullet/81/81_14.pdf
 
J

jlowers

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Re: 340 mercruiser coolant out exhaust

Bt Doctur said:
If your He cools the exaust manifolds and your HE waste water cools the risers you need to block them off.There are no slotted SS plates only solid ones. You can use aany slotted gasket, then the SS block off plate, then another slotted gasket.see page 5
http://www.boatfix.com/merc/Bullet/81/81_14.pdf
Click to expand...

Thank you, you are correct. When we pulled a riser off it did not have a solid plate, it was slotted, also the new riser came with a slotted stainless plate. Apparently when the mechanic put new manifolds and risers on last year he did it wrong on both sides! We have been running for over a year mixing coolant with salt water! No wonder we had coolant loss and overheating:mad:

Installed two new blocking plates and all is well.

Thanks again for your time.
JJ
 
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