Author Topic: CVX EXHAUST  (Read 1161 times)

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Offline Glastronjohn18

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CVX EXHAUST
« on: July 09, 2022, 10:38:46 PM »
Several weeks ago Betty and I were returning from a short cruise up the Seneca River and as we approached the dock there was smoke coming from the engine compartment along with the smell of hot rubber. We got to the dock and found the starboard side exhaust smoking hot with some of the boots ozzing  melted rubber. Diagnosis found the starboard external water passage almost completely plugged, the port side was not as bad.




After getting the boat home I started the search for new manifolds and risers. Although the drive train is Mercruiser the exhaust is Volvo Penta as
I did thru hull exhaust when I repowered with the 351. The factory only offered log manifolds during the time they used Ford engines so I used VP center riser manifolds from a '96 boat. The manifolds worked well except the risers were so tall that I had to raise the front of the engine cover several inches to get enough clearance so the risers would not contact the cover. As long as I'm getting new manifolds I'll try to get something that fits under the stock cover.




Barr makes a small block Ford manifold for Indmar and PCM with the same short riser used on Mercruiser's GM applications. This combo lowers the overall  height by 1 1/4 in.
These are the Barr manifolds and risers





The Barr risers are several inches shorter than the VP ones.






Here the Manifolds are installed. The height of the Barr manifolds are about 3/4 in. taller that the VP's.




Here is the finished install. The overall height allows the engine cover to be returned to it's original position.








All back together with good water flow.





Beyond correcting the water flow problem there are several positive changes.   The Barr manifolds and risers allow the engine cover to be lowered to it's original position and because there are no external water passages sparkplug access is a breeze. With the VP manifolds the external water passages blocked sparkplug access. To get at the plugs the exhaust manifolds had to be removed. The only short coming of the Barr manifolds I see is that there are only 4 bolts per manifold instead of 8.

Overall I'd say this project is a success. One last thing to do is a test drive.






« Last Edit: July 09, 2022, 11:27:29 PM by Glastronjohn18 »
John
'80 CVX 18 - Survivor Class
'78 CVX 18
'76 V 225 -   Bal Harbor
'80 V195XL
'86 CVX 18- And '86 Makes 3

Offline Plugcheck

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Re: CVX EXHAUST
« Reply #1 on: July 10, 2022, 02:26:07 AM »
Having to remove the manifolds to change plugs sounds like a huge PITA.   Curious to know if you plumbed the new manifolds as wet or dry joint?, Looks like the ports were available to do either way.  Given my druthers, I'd opt for dry joint everytime.     As for the old ones, could they be "boiled" out with some muriatic acid?  Looks like you did a great job with the swap, hoping your lake/river testing goes well!      On a little side note, generally if you see steam from the exhaust, it can be an indication the impellor is weak.   Most noticable when coming off a run back to idle.  Just a thought to check.   I assume your manifolds clogged with rust or sand/mud?
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude

Offline Glastronjohn18

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Re: CVX EXHAUST
« Reply #2 on: July 10, 2022, 09:29:57 AM »
Yep. Huge PITA to change plugs so much that they were the same one in the engine when I installed it in 2019. I went with wet as I couldn't find much info on PCM or Indmar cooling systems. Several years ago I did a carb rebuild on a friends Master Craft with a Indmar 351, it had wet joints. That experience plus not having to change T stat housings and extra plumbing sealed the deal. It was smoke not steam that we saw. However the impeller was the first thing I checked. Vane were intact and plyable with good water flow at the T stat housing. Manifolds were clogged with rust. I couldn't see much light from a flashlight shined through the exterior water passage. A 1/4 rod would not go through. Thought about "boiling " them but being used and 27 years old I don't know how much life is left in them and I have seen several motors replaced because of water ingestion through the exhaust so I went with new.
John
'80 CVX 18 - Survivor Class
'78 CVX 18
'76 V 225 -   Bal Harbor
'80 V195XL
'86 CVX 18- And '86 Makes 3

Offline Plugcheck

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Re: CVX EXHAUST
« Reply #3 on: July 10, 2022, 09:59:24 AM »
 I think they(Mercury?)came up with it when big blocks were having issues.   I might be wrong, but converting to dry joint is adding the short water connecting hose at the riser, and using the blocking gasket.   My CVZ does have the thermostat housing with two lines to the risers, the Timi does not..  The wet joint has worked well for years, you just don't know if water leaks occur into the exhaust  untill it sucks up water. 
Michael
1979 CVZ-18 388 CI Vortec Mouse
1980 CVX-16SS 140 Mercruiser
1979 CVX-16 Johnson 175
2002 Bennington 2275CC 90 Mercury
1985 Intimidator project
1989 Lowe 200 Redneck fishin Toon
2001 Godfrey Sweetwater pontoon 115 Rude