Budman

Has anyone ever done this? If so, how, and what were the results? I have a stock Merc exhaust behind my 454, and it was suggested to me that a few more ponies might be gained by limiting the amount of water that is introduced in the exhaust stream. Would this work without getting the hoses too hot?

Thanks for the input!

Cord

I wouldn't mess with it. The results wouldn't be worth your troubles. If you want to make some improvements, you could go to a set of after market manifolds. If you get the right set you'll improve the scavange and lose some weight.

cigarette1

Go to your local Speed Shop and ask for water restrictors. The sell them in sets of three(Holley). They look like large washers and each has a different size hole in it. They fit in your thermostat housing. Side note: they will also increase your water pressure.

G

candyman35

Budman,
Don't do it. Like Cord said it could raise your water pressure. The sea water pump will flow a set amount of water per given RPM. The water has to have some where to go. If it is restricted the water will build up pressure in the engine causing circulating pumps to go bad, possible gasket failures etc. A good set of exhaust manifolds would be a better choice.
Dan

MitchStellin

Yes, leave it alone. You won't even see the increase but you will see water in your oil.

Tinkerer

I have lightning headers-- but I also restrict the water by bypassing some of the water that goes to the top elboes and send it overboard. I spray it on the drives. If you bypass too much water it will burn up the exhaust hoses. I have done this on stock sxhaust also and it helps lean out the motor. ( this means more HP)

Budman

Tinker,

Can you elaborate on how you set it up with stock exhaust?

As a side note - I noticed on another thread that was discussing closed cooling that Merc and Crusader both used a stainless plate to block off the water passage between the manifold and riser. Would there be any advantage to using one of these, and then installing a bypass hose to the riser, possibly with some type of restricting device to decrease the water flow to the exhaust stream, and dump the remaining water?

Thanks for the replies! I would love to install a set of headers, but I don't have the $1500 - $2000 it would cost for them. I don't think I would see enough gain from a set of manifolds to make it worth my $$$ - If I had that to spend, I would probably put it toward some better heads.

Offshore Addiction

budman,your absolutly correct about a few extra ponies,but you do not want to decrease the water in the exhuast.....the water coming out through your exh takes up approximatly 30% of the capacity of your through hulls(assuming you have through hull).what you need to do is gain extra capacity by enlarging your pipes,including your though hulls......stainles marine helped me develope this theory back in 00 in my factory boat....you need to get 5inch tips that decrease to 4 1/2 inch inside and step your hoses up on your risers to accout for the 4 1/2inch hoses.......this theory has been proven to work.it increases the capacity to account for the water volume in the pipes....it was all I could do,and the carb motors had a dry cheater pipe they could use that still was acceptable to APBA specs(they still had the wet hose connection they reqiured).Needless to say,you wont find a factory class motor without these now.......

Budman

Offshore,

So you had an inner dry pipe that ran inside the 4 1/2" hose to carry the exhaust all the way out to the transom? How did you attach it to the riser? What type of material was it made of? Did you use stock risers?

Any details you can provide would be appreciated.

Offshore Addiction

NO,just enlarge your wet hose,gives you the same volume as a 4 inch dry pipe,when you get to the tip,the tip starts at 4.5 and ends up at 5,kinda like a megaphone......on the riser end,just cut a piece of the 4 inch hose about 2 inches long,shove it on the riser,pop a 4.5 inch hose over the sort piece and clamp it down....