4,3 Volvo Penta Riser Extension = PURPOSE

alan ber

Petty Officer 2nd Class
Joined
Jun 29, 2008
Messages
143
I have twin 4.3 Volvo Penta engines on my Regal
Needed too get too Kohler Gen ,
Difficult too reach areas of gen set since its tucked under deck and riser of port engine stops my arm from reaching

Removed riser & external oil filter , ,

Have supply of green Volvo Penta gaskets ( from previous owner ) ,


Riser & manifold was changed 10 months ago , ( new long blocks , shop used Sierra )

Boat used in salt water , ,
10 months , 75 hours since new long blocks , CRUD in water passage ? , Flush engines after each use ,

Next agenda is too removed other risers & making sure they are clean


QUESTION
Purpose of 3 inch extensions or any extension under riser , NECESSARY ?
Original design a table top is stored under deck ,. Since new manifolds / risers top hits risers and deck
lid can not close flush


thanks as usual
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
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47,306
QUESTION
Purpose of 3 inch extensions or any extension under riser , NECESSARY ?
Original design a table top is stored under deck ,. Since new manifolds / risers top hits risers and deck

If risers were added, they are necessary. That means your boat is heavy, and sitting low, and the elbow to static water line measurement was less that 14"

If you remove the risers, most likely you will end up hydro-locked because water will fill your engine thru the exhaust.
 

alan ber

Petty Officer 2nd Class
Joined
Jun 29, 2008
Messages
143
Scott
I was thinking prior too my post , Has too be a reason why a 3 inch extension is use
On my Volvo , manifold , then 3 inch extension , then riser gets bolted too extension

Was curious , looks like riser would connect directly too manifold , Purpose of Extension adds more height would stop
back flow ? . higher over engine ,

I had no plans on changing just curious why the use of an extension
 

Bondo

Moderator
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Apr 17, 2002
Messages
70,468
I had no plans on changing just curious why the use of an extension

Ayuh,..... As Scott said, the bottom of the exhaust cavity, inside the riser, HAS to be 13.5" or higher, than the waterline, outside the hull,.....
 

Lubak572

Petty Officer 1st Class
Joined
Jan 4, 2018
Messages
235
So along that line would it be beneficial to run taller ones when replacing if clearance isn't an issue. Would it hurt cooling or performance?
 

Bondo

Moderator
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Apr 17, 2002
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70,468
Ayuh,..... Either you have the height, or ya don't,.....

Addin' extensions ya don't need just adds weight, 'n expense,....
 
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