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manifold conversion?

8

805HD

Regular Contributor
What's up guys, been boatless for a while but recently picked up an old formula f20 with a 351 Windsor in it. Has the old log style manifolds currently. If I go to through hull exhaust I'm assuming I would have to switch to the newer center riser manifolds? Is that possible? Not seeing much on the subject...

*This post is not about pros and cons of going through hull or how much you absolutely hate noise pollution. lol

I found a guy with a new set of Barr manifolds and Sierra risers about an hour from me, they are for a 351w but listed as an OMC replacement so I'm not sure if that would swap over to merc or not.

Thanks in advance! Glad to be back!
 
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I would make sure the engine is on decent shape before dumping $$ trying to upgrade it...same for drive condition.

Ford engines have not been offered as new equipment, I the boat world, for decades...existing support is limited and continues to shrink.

The engine should be happier with thru transom exhaust. I would go with the center risers as they breathe better than the logs and are likely to have parts available for a while..
 
If you were using only thru the transom exhaust the OMC parts might work, they are available because Volvo used the same engines during the joint venture time period, I think Barr makes replacements for those. If you were going to try to have a switchable system where you could switch from thru the transom to the underwater exhaust via the outdrive transom mount I don't know if that would work, due to you having a Merc Y pipe, Depends on exhaust height, angles, etc.
 
louc said:
If you were using only thru the transom exhaust the OMC parts might work, they are available because Volvo used the same engines during the joint venture time period, I think Barr makes replacements for those. If you were going to try to have a switchable system where you could switch from thru the transom to the underwater exhaust via the outdrive transom mount I don't know if that would work, due to you having a Merc Y pipe, Depends on exhaust height, angles, etc.
Click to expand...

The boats gutted, and I never trust a manifold I just met. So, I’m going for two birds one stone here.

The Y pipe is still in play but I’m pretty sure they make a kit to delete that. Block off plate?

Anyways, the point is I’m working with a blank canvas.

I know the manifolds will fit, but what about the plumping of the manifolds themselves. I’d imagine all raw water exhaust systems work the same way more or less. Water in and water out.

Maybe have to swap some hoses around?
 
Look in the OMC section of the catalogs on this site, and you'll see how the 5.8 engine was set up, the OMC cooling system is very simple, there is just one hose feeding each manifold coming off from the thermostat housing. Those hoses are 3/4" ID, I'm not sure what Merc uses, but I'd guess the same.
Example:

I converted my old 4.3 V6 from the OEM OMC batwing manifolds to the later style OMC/Volvo exhaust using Barr exhaust parts, they are decent quality, just make sure to check the sealing surfaces for flatness.
 
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