A Homemade out the back exhaust..............whoooooweee!

[Manipulator]

I have a Chevy 350 (OMC unfortunately) in my 1983 Sea Ray SR225. Anyway, I noticed the other day the damn exhaust riser on one side is cracked and leaking. I will have to get a new one. Right now my setup is the exhaust goes down and out the prop. I was debating on getting a set of 90 degree riser elbows (mine currently come up off the manifold and then pivot down about 45 degrees) and some stainless steel pipe and run those bad boys right out the back. I have caps (Home Depot rubber caps for 3" PCV pipe) that I could put over the inlets with clamps where the exhaust connects into the lower unit. All I really would need is the risers, rubber reducers from riser elbow to exhaust pipe or muffler (Home Depot has 3" to 2" rubber connectors that fit perfectly- I know these aren't marine but they will work as its a water-cooled exhaust so I don't really see a problem - do you? That is with heat. I imagine the marine bellows can handle some heat but I have 3" connectors from Home Depot on there now and don't have a problem with heat. I looked inside them and they looked fine), I also would need about 1 foot of stainless pipe and the stainless sleeves for the transom. Anyone ever do a homemade job? I think it would work but would be too loud. Since the exhaust is blended with water, would it be quieter than straight exhaust? What if I bought the stainless mufflers that have the tips already installed? Afro technology at it's finest. Any thoughts?

 

[navigator336]

Re: A Homemade out the back exhaust..............whoooooweee!

It will be loud without the mufflers. The water quiets it a little, but it will still sound like headers. I would be a bit concerned about the exhaust gases reacting over time with the home depot rubber. It may be fine, but check it frequently like you have been doing. I'd carry a spare 3" cap in case the one which will go on the outdrive gives way (and double hose clamp it). Depending on where the cap sits relative to waterline, you will have some pressure on it(1 foot of water head height = about .5 PSI) Rather than going 3" to 2" to stainless pipe to the exhaust tubes, why not go 3" marine exhaust hose from the risers to the mufflers?

 

[Manipulator]

Re: A Homemade out the back exhaust..............whoooooweee!

I happen to check the other hose connection and riser on the other side. Inside the hose it looks a little blistered. The previous owner had the lower unit rebuilt and also had new exhaust manifolds put on. they didn't replace the risers but did replace the bellows or exhaust hose connectors with what appears to be 3 inch rubber sewer hose from a hardware store. I went to home depot and what they have looks exactly the same. This was all done probably 5-7 years ago. It seems to have held up but the blistering has me worried. I would imagine marine grade exhaust hose (to connect elbows) has a high heat tolerance. Or does it? I mean the system is a wet system so it can't get that hot.<br /><br />The exhaust inlet in the out drive where I would put the caps on, is about 6 inchs above the water line. <br /><br />why not go 3" marine exhaust hose from the risers to the mufflers?<br /><br />Excellent idea. I'm trying to make this a low budget project. I think a 5.7 would sound great with pipes out the back. I don't want it too loud but I'd like it to sound good. I guess if I bought the 3 inch exhaust hose (marine) I really wouldn't need any home depot cheap rubber connectors. It would be the riser connecting to marine 3 inch exhaust hose, connected to mufflers and out the back. Hopefully I can find mufflers with long tips that will go right through the transom.

 

[navigator336]

Re: A Homemade out the back exhaust..............whoooooweee!

I used to have a tri-hull with a 351 Cleveland with the four barrel heads running with risers and no mufflers through the transom. It was loud but not like a blown big block with dry or wet stacks. It did sound good, but required the stereo being cranked up alot.

 

[cc lancer]

Re: A Homemade out the back exhaust..............whoooooweee!

All I really would need is the risers, rubber reducers from riser elbow to exhaust pipe or muffler (Home Depot has 3" to 2" rubber connectors that fit perfectly- I know these aren't marine but they will work as its a water-cooled exhaust so I don't really see a problem - do you? That is with heat.<br /><br />These home plumbing pipe connectors will not handle the heat.<br />It will sound good for a while, then it will get old, go in the pits of a local race track and listen to a 350 with straight pipes.

 

[Manipulator]

Re: A Homemade out the back exhaust..............whoooooweee!

What about with mufflers? <br /><br />So where can I get some marine 3" exhaust tubing cheap? I only need like a 4" section. I looked online and they want $25-$40 for that dinky piece of rubber.

 

[navigator336]

Re: A Homemade out the back exhaust..............whoooooweee!

Even at West Marine it's only $17/foot. You should be able to get it for about $12/foot on the internet, but shipping will negate any savings. You could try a local repair shop to see if they have a scrap. I think you'll need more than 4" though. The riser connection alone will take about 3".

 

[mkast]

Re: A Homemade out the back exhaust..............whoooooweee!

Go to NAPA for real marine 3 inch exhaust hose.

 

[salty87]

Re: A Homemade out the back exhaust..............whoooooweee!

nobody ever said boating was cheap, if you're gonna do it you might as well use marine approved parts....unless you like checking your HD hoses all the time

 

[Manipulator]

Re: A Homemade out the back exhaust..............whoooooweee!

All I need is 4 inchs that is it. Marina in town has it for under $7 per foot.

 

[navigator336]

Re: A Homemade out the back exhaust..............whoooooweee!

Well, if you can get the mufflers and exhaust tubes at a decent price, it should work out nice.

 

[flashback]

Re: A Homemade out the back exhaust..............whoooooweee!

I wouldn't use those rubber plumbing parts on a bet... what if your water pump craps out??? the exhaust from your engine will melt them in a heartbeat before you even see it on the temp gauge... GOOD LUCK BROTHER.......

 

[Manipulator]

Re: A Homemade out the back exhaust..............whoooooweee!

Well after looking it over I decided it's easier just to by a boat that has the thru-hall exhaust option. Not that I'm going to run out and do that. This boat has plenty of life left. <br /><br />It pretty tight in the engine compartment and I would have to buy a set of fiberglass (20 degree) exhaust elbows with hose. That really isn't that expensive. Mufflers would be hard to do as there just isn't much room from the riser to the transom for the fiberglass elbow, exhaust hose and then muffler. Definitely would have to be straight exhaust which would be pretty loud, although someone said it's not that loud on a wet system. The main problem is the exit. The swim deck is in the way. If I go above it then the shift linkage and power steering rack that's in the way. I could go under the deck but am afraid I'd be right on the waterline. Unfortunately it looks like it's not worth the trouble. Besides, now that I think about it, I would want a silent choice option. How about I run the pipes straight up like stacks on a semi truck lol!

 

[flashback]

Re: A Homemade out the back exhaust..............whoooooweee!

I had the same concern as you regarding the swim platform. we ski and board a lot and the pipes in the back just won't do, although I have thought about going out the sides of the boat kinda like an old buick..

 

[Manipulator]

Re: A Homemade out the back exhaust..............whoooooweee!

Cool! I like the way Crownline does that. Another great boat, think it went out of business was Mariah, and they too ran pipes out the side.