Volvo Penta SX-M Exhaust Flappers

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I understand that there is a technical bulletin on dealing with the y-pipe when flappers are removed. Just wondering where you would find that? I pulled off my leg and am in the process of replacing the u joint bellows when i came across two flappers, one loose in the y-pipe and one lodged in the exhaust bellows and would like to patch the holes where they used to be located.

Also have any volvo penta SX-M owners had any problems once they did remove the flappers?
 

Lou C

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There is a service bulletin on this procedure.
I think that Volvo added check valves in the exhaust risers to prevent water from getting sucked back up the exhaust . Might want to investigate these
 

mikeneal

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My flappers got hurt when it overheated about 10 yrs ago, I did riser gaskets at same time and used longer silicoe hose to cover the holes .
 

bruceb58

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There is a service bulletin on this procedure.
I think that Volvo added check valves in the exhaust risers to prevent water from getting sucked back up the exhaust . Might want to investigate these
Nope...same risers as before.
 

Lou C

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http://www.volvopentastore.com/Exhau...view_id.791178

​The risers are the same but they added the check valves, to prevent the engine from sucking water back up the exhaust. Part # 5. I believe it allows air to enter when a vaccum is formed in the exhaust, but is a one way valve so exhaust can not exit that way.

https://www.ebay.com/itm/VOLVO-PENT...AIR-CHECK-VALVE-3857761-HI-PERF-/164018500917
s-l300.jpg
 
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bruceb58

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http://www.volvopentastore.com/Exhau...view_id.791178

​The risers are the same but they added the check valves, to prevent the engine from sucking water back up the exhaust. Part # 5. I believe it allows air to enter when a vaccum is formed in the exhaust, but is a one way valve so exhaust can not exit that way.
Those valves had always been on the 4.3L Volvos even when they had the flappers. Probably more for reversion prevention purposes than to replace the function of the flapper which was to prevent water from entering back from the drive.
 

Lou C

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Looking back it seems that they were added during the joint venture era maybe because of differences between the non vortec and the vortec engines. I don't see them on any of the pre 1994 engines I looked at on the volvopentastore.com
 

bruceb58

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They were on 95 and 96 and those were pre Vortec. Thought we were talking about SX here. 94 was a different drive entirely.

Typically, marine engines did not see the Vortec heads until 97.
 

Lou C

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Wasn't '94 the start of the Joint Venture, with Volvo and OMC selling basically identical engine packages with the OMC still being called the Cobra, and the Volvo called the SX Cobra, later they dropped the Cobra part of the name?
​Looking at the Volvo online parts catalog, unless you are hip to their arcane model number system, it is impossible to figure out model years, unless they have a conversion chart somewhere. OMC's part system was much simpler, being classified by model year and engine/drive model #s.
​Anyhow, using OMC's easy to navigate catalog, I see they were added for the '98 model year 4.3s, but not earlier.
​However, judging by the different valve covers used on the non vortec vs the vortec models, the last year for the non vortec was '98. All years '94 to '98 appear to have 4.3 Vortecs due to the different style of valve cover used. Now this is what OMC did, not sure if Volvo really sold the same engine packages from 94-98 or what. My only point is that those valves may or not be needed, esp if the static water line is not high enough in certain installations.....
 

bruceb58

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You are correct...joint venture started in 94.

For Volvo the MD model was 94.

You can't tell from the valve cover if it's Vortec. Only intake manifold.

I think you are correct...the valve was added starting with the Vortec heads.
 

Lou C

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On the V8 small block you are correct, but on the V6 it says V6 VORTEC in big letters on those valve covers.

The non vortec intake like mine has 12 bolts and the vortec only has 8, also the non vortec has an exhaust crossover, while the vortec doesn't That is why vortec engines have to use electric chokes if they are carb engines, no source of manifold heat to open the choke. I have been researching OMC bat wing conversions for a long time, and one of the first ones was put out by OSCO. And I recall that they said "not for use on Vortec engines" so there must be some difference in the exhaust dynamics between the 2 engines and it may be a bigger deal on the V6 than on the V8. I finally settled on using the Volvo style exhaust for ease of getting parts and not having to use lousy aftermarket like GLM, they were the only conversion kit on the market. Of course doing it my way was more expensive, because those Volvo OE 90*exhaust pipes that convert from the 4"riser hose to the 3.5" Y pipe hose are about $200 each. But then for future replacements you can use Barr manifolds which are good quality and reasonably priced. In fact they may actually cast V/Ps manifolds....
 

bruceb58

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On the V8 small block you are correct, but on the V6 it says V6 VORTEC in big letters on those valve covers.
It's interesting that a 95 and 98 4.3L engine valve covers have the identical part number even though the 98 is a Vortec. GM makes the valve covers.

Here is a 99(Vortec):
http://www.volvopentastore.com/Cylin...view_id.791145

Here is a 2000:
http://www.volvopentastore.com/Cylin...view_id.768610
One side(starboard) has the Vortec listed on it but the port side is the same part number as the 95(pre vortec).


Not that this really matters though. For the person who wants to change to Vortec heads, they just don't need to change valve covers.
 
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Lou C

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Interesting I did the same thing with the OMC catalog, in theirs the part numbers are different for vortec and non vortec.
​I briefly considered converting my engine to vortec heads, manifold, etc but there were too many unknowns, and not knowing anyone directly who had done it, I elected to just replace what I had. There are apparently a few subtle differences and you really have to know your stuff to do it right. Even within the Vortec series there are more differences, some had adjustable valve train and some do not. So I got a set of remanufactured heads with the same casting #s as what I had and was able to re-use my old intake manifold. Tried to keep it simple.
 

Maclin

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Regarding reversion on the 4.3, I was following something in the MerCruiser forum where achris had posted that Merc had a bulletin out for the technicians to not run below 1200 rpm (or 1500 maybe, not sure now) when on the muffs. This was aimed directly at avoiding reversion in the 4.3. Maybe Volvo engineers had witnessed the 4.3 tendency for reversion also and came up with that valve?
 

Lou C

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I found an old positing from Don S on this subject, but not about the valve. It was about the 90* elbows that connect from the 4" riser to the 3.5" Y pipe. It seems that Volvo re-designed this part, from the style OMC was using which was a more typical 90* elbow to one that looks wider across the back, like a King Cobra ready to strike as he said. He indicated that they were finding reversion with the conventional elbows but not with this one. I guess they added the valve as well to be on the safe side....You can see the V8 models from both VP and OMC used the conventional elbow but the V6 models used one with a different angle, presumably to keep water from getting sucked back up the exhaust....
 

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bruceb58

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Current Volvo risers are the same for the V6 and V8 engines.

383061 is the part number up to 2011 engines

Even the 7.4L Volvo in my sig uses the same exact risers.
 
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Lou C

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I mean the elbow that connects from the 4" riser hose up top down to the 3.5" Y pipe. That is the part that was revised by Volvo. Part #12 (V6) vs part #27(V8) in the pix I posted above......see how it's totally different V6 vs V8. That's right off VP's parts website.
 

bruceb58

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OK...got it. A lot of people call the risers elbows.

Reading comprehension is not good for me today
 
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