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Possible exhuast reversion issue

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Possible exhuast reversion issue

Old 07-26-2022, 05:15 AM
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Default Possible exhuast reversion issue

I am doing a restoration to my 1985 Velocity 220 with a major redo over the off season. I've been taking care of a few things that can be done during the season and one of those is a new better breathing exhaust. I decided to go with a Stainless Marine Hi Torque 4 inch exhaust. A step up from the basically stock HGE-7114-A with Imco 4 inch stainless riser that were on the boat. I notice that the exhaust was kind of flat from the manifolds back to the tail pipes, and I was right. When the Stainless Marine exhaust is used you first bolt on the manifolds and then take a number of measurements and email those to Stain Marine. They then make up the risers from the measurements you supplied. I was contacted by Jerry and Letty yesterday from Stainless and they showed some concern with the lack of drop in the exhaust since I only have so much room under the deck and I really don't want to cut anything. I'm also against a dry exhaust. They told me that there were some tricks they could use to minimize any reversion issues by adding an anti reversion ring and moving the water tube back farther closer to the tailpipes.I never had a problem with the old exhaust, but a new engine will be built over the winter with a much more aggressive cam profile and obviously I don't want any reversion when the new and expensive engine goes in. Does anyone have any suggestions, trips or tricks in dealing with this issue in the older Velocity 220s. TIA
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Old 07-26-2022, 06:39 AM
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Can you go with dry exhaust to the tip and add a muffler tip or route the water through the hull and dump into the tip? Just asking, have similar concerns with up coming mods.
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Old 07-26-2022, 08:04 AM
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Originally Posted by Helmwurst View Post
Can you go with dry exhaust to the tip and add a muffler tip or route the water through the hull and dump into the tip? Just asking, have similar concerns with up coming mods.
I'm going to wait and see how this all turns out with Stainless Marine before I decide what is needed and what the final result will need to be. Right now the ideas that are on the table are an anti reversion ring and moving the nipple back on the riser as far as possible. Hopefully that will be a satisfactory way to proceed. I was just asking to see if there were any other older 220 owners that ran in to this issue.
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Old 07-26-2022, 10:23 AM
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if whoever spec'd and built your motor is a knowledgeable and reputable marine guy, he should be able to tell you if you will have reversion issues and what you need exhaust wise as exhaust is part of the entire engine building equation,
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Old 07-26-2022, 10:28 AM
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When I had my 22 velocity I had a BBC with Stellings headers in it. I raised the hatch 4", which wasn't difficult and I had the tips redone on the headers to fit back in the original transom location. Why are you against dry exhaust? They are louder but its not bad.
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Old 07-26-2022, 11:34 AM
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Dry exhaust isnt too bad IN the boat, its your blowboat neighbors that hate it. Personally its music to my ears
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Old 07-26-2022, 11:51 AM
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Originally Posted by phragle View Post
if whoever spec'd and built your motor is a knowledgeable and reputable marine guy, he should be able to tell you if you will have reversion issues and what you need exhaust wise as exhaust is part of the entire engine building equation,
The engine builder is Tony Bischoff-BES Racing Engines so I guess that part is covered. It was the exhaust builder that has been showing concern. The post was inquiry for those that has the same boat as to what they did with this issue.
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Old 07-26-2022, 11:57 AM
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Originally Posted by cdail28590 View Post
When I had my 22 velocity I had a BBC with Stellings headers in it. I raised the hatch 4", which wasn't difficult and I had the tips redone on the headers to fit back in the original transom location. Why are you against dry exhaust? They are louder but its not bad.
I am against dry headers because yes they are loud, but the larger reason is I don't want to cut a larger holes in my transom. I'm not sure how that would pan out when the Bravo drive goes in. The boat is a real deal 1985 Steve Stepp Kevlar deck Velocity and I am against any cutting on the boat. I also don't want to raise the engine hatch as I want to keep the boat looking like it did when delivered in November of 1984. After all it's not a Baja and they are becoming farther and fewer in between. In the end I want the boat to look stock, but not run like it's stock. A sleeper one might say.
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Old 07-26-2022, 12:18 PM
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Originally Posted by Donnie D View Post
The engine builder is Tony Bischoff-BES Racing Engines so I guess that part is covered. It was the exhaust builder that has been showing concern. The post was inquiry for those that has the same boat as to what they did with this issue.
I'm sure that BES is more than able to tell you if you are going to have reversion issues with that exhaust and cam. SM has already told you that they are concerned, so I'd hope that BES is also.
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Old 07-26-2022, 12:27 PM
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Mercury Racing gives out installation instructions for their motors and exhaust for just the reason you are asking. They don't want reversion either. To save you time looking it up, they tell you that on a basic stock motor (350/454/502 etc) you need at least 13" from the top of the exhaust elbow to the waterline.

On a performance motor they want 15" from the waterline to top of elbow, and a minimum of 1/2" drop per 12" of exhaust.

If you can't get to those numbers with the stock locations then you are going to need to do dry or some other "fix" to eliminate the risk of reversion. I'd ask SM if their suggestions are just going to help, or if its going to stop reversion. I'd ask your engine builder and cam picker the same questions about reversion.
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