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Discussion Starter #1
Ok, I am seriously-Newbie at boats. But, I have been building hi-perf cars for over 20 years. Don't laugh too hard if what I propose is so ridiculously stupid, just slap me and set me straight!

So, I bought a 19' bow-rider ski boat project (floor, stringers, engine mounts, transom, I think this thing was "sunk" in someones driveway for 10 years!) I am in the process of redoing it all myself.

The engine and drive are perect! Not even a leaky valve cover, very very little hours. It's a 305/Alpha One combo, 205hp 2bbl. Not really a "Performance Boat"... yet! That's why I'm here!

So while its all out, me being a speed guy, I want to block off the exhaust and run thru the transom. To save the stern drive all that heat, and free up some horsepower. I was thinking of building my own exhaust (because I can) but, and here's the big Q, is it possible to run the exhaust without water? I also have a single draw-thru turbo setup from the old Pontiac Turbo Trans Am I was thinking of running on it. It is not a boat turbo, no water jackets. So am I going to burn the boat down and sink it? Or is there an alternative to water cooled exhaust (I was thinking of wraping everything double with header wrap).

Can it be done? I have a pair of Rams Horn manifolds I was going to wrap them in header wrap, turn them upside down and build my own up-pipes, Y- the two into the turbine housing and run a single downpipe with a 6" riser and out thru the transom. The turbo should be good for 350hp on 10psi.

Next Q, can I run a closed cooling system and ditch all the hoses and other crap, just run a single radiator/electric fans or lake water heat exchanger? Again, be easy on me, I am a car guy, I have my car ideas, maybe they will work or maybe not. What say you all?

Thanks for your time guys.
 

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Ok, I am seriously-Newbie at boats. But, I have been building hi-perf cars for over 20 years. Don't laugh too hard if what I propose is so ridiculously stupid, just slap me and set me straight!

So, I bought a 19' bow-rider ski boat project (floor, stringers, engine mounts, transom, I think this thing was "sunk" in someones driveway for 10 years!) I am in the process of redoing it all myself.

The engine and drive are perect! Not even a leaky valve cover, very very little hours. It's a 305/Alpha One combo, 205hp 2bbl. Not really a "Performance Boat"... yet! That's why I'm here!

So while its all out, me being a speed guy, I want to block off the exhaust and run thru the transom. To save the stern drive all that heat, and free up some horsepower. I was thinking of building my own exhaust (because I can) but, and here's the big Q, is it possible to run the exhaust without water? I also have a single draw-thru turbo setup from the old Pontiac Turbo Trans Am I was thinking of running on it. It is not a boat turbo, no water jackets. So am I going to burn the boat down and sink it? Or is there an alternative to water cooled exhaust (I was thinking of wraping everything double with header wrap).

Can it be done? I have a pair of Rams Horn manifolds I was going to wrap them in header wrap, turn them upside down and build my own up-pipes, Y- the two into the turbine housing and run a single downpipe with a 6" riser and out thru the transom. The turbo should be good for 350hp on 10psi.

Next Q, can I run a closed cooling system and ditch all the hoses and other crap, just run a single radiator/electric fans or lake water heat exchanger? Again, be easy on me, I am a car guy, I have my car ideas, maybe they will work or maybe not. What say you all?

Thanks for your time guys.
Lets start with the closed system. Yes you can run a water to water heat exchanger. Don't even consider a water to air radiator AT ALL!
The closed system is most popular on boats that run in salt water alot, and on newer boats running EFI and trying to keep the engine temps consistent. There is no real advantage to running a close system other wise. And just another thing to complicate the boat, the cooling system, more components, more weight, blah blah blah. Not worth it.

NO! You can not run uncooled exhaust if the engine is under a hatch, at all, even occasionally. Uncooled heaters are used all the time in race boats, specifically drags and circle racers. You will not be able to have back seat passangers AT ALL, and you will not be able to have rear interior AT ALL. This is not a maybe, or I'll wrap it, or..... NO! Doesn't matter if its steel tubing or cast horns upside down. NO!
Its a outdrive which means it has more freeboard(deeper) than a flat bottom or jet. The deeper the engine sits in the boat, the more NO, DO NOT TRY IT!

throw on the turbo, and everything I just said about the exhaust is now tripled.

don't mean to sounds abrupt, but your into a serious, dangerous issue here.

PS, you are aware that replacing the stringers in your boat is paramount to replacing and rebuilding the fram of a car. It is the boats back bone. If it fails, it is not going to be pretty. And it may not fail slowly with warning. Fiberglass is like that sometimes. Make SURE you know and understand what you are doing.



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Discussion Starter #4
@GN7, thank you! That is exactly what I needed, a slap in the face, DOH! I knew I was into a completely new realm here with this boat, that's why I asked. I see these 4" stainless exhaust risers that replace the factory merc elbows, I assume they are double wall pipes with water jackets, eh? I was thinking I could do fabricate all that myself and save big bucks. The only thing I don't have is a water jacketed turbine housing, but I suppose I could find one to fit my turbo. I deal with a turbo guy in Lake Havasu City... I think he'd probably know a thing or two about boat turbos, too.

It appears the water leaves the jacketed risers and enters the exhaust stream at the first rubber connector. I can't have water going through the turbine housing in the exhaust. So as long as I inject water into the exh AFTER the turbine housing, it should be ok? Add to that header wrap on the outside of the downpipes for added cooling. The only problem then is how to separate the water and exhaust long enough to go from the factory risers to the turbine housing (using 4" pipes with 2" pipes inside, plumbed to run water in between.) I don't know how to separate the water except to use an aftermarket or homemade riser.

I'll keep the cooling system like it is. Easier and sufficient. Can't beat cool lake water for a heat exchanger!

I won't even get into the Alpha One in this forum. My target is "only" 350hp and about the same torque. Hopefully it'll live for a while.

As for the boat, I have an experienced boat worker helping me design and fabricate the repairs. THAT is one thing I don't want to screw up.
 

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@GN7, thank you! That is exactly what I needed, a slap in the face, DOH! I knew I was into a completely new realm here with this boat, that's why I asked. I see these 4" stainless exhaust risers that replace the factory merc elbows, I assume they are double wall pipes with water jackets, eh? I was thinking I could do fabricate all that myself and save big bucks. The only thing I don't have is a water jacketed turbine housing, but I suppose I could find one to fit my turbo. I deal with a turbo guy in Lake Havasu City... I think he'd probably know a thing or two about boat turbos, too.

It appears the water leaves the jacketed risers and enters the exhaust stream at the first rubber connector. I can't have water going through the turbine housing in the exhaust. So as long as I inject water into the exh AFTER the turbine housing, it should be ok? Add to that header wrap on the outside of the downpipes for added cooling. The only problem then is how to separate the water and exhaust long enough to go from the factory risers to the turbine housing (using 4" pipes with 2" pipes inside, plumbed to run water in between.) I don't know how to separate the water except to use an aftermarket or homemade riser.

I'll keep the cooling system like it is. Easier and sufficient. Can't beat cool lake water for a heat exchanger!

I won't even get into the Alpha One in this forum. My target is "only" 350hp and about the same torque. Hopefully it'll live for a while.
There are exhaust systems where the water jumps externally thru a rubber hose, from one component, like the header manifold itself, to the riser, or to the tail piece after the turbo, and the water doesn't enter the exhaust stream until the very end. You can pretty much choose to have the water enter the exhaust stream anywhere you wish by picking a choosing the right jacketed compaonents. But for the most part, there no, zero, parts of the exhaust that isn't either cooled by double wall jackets, or the water in the exhaust stream. The sooner the water enters the exhaust stream in the system, the more power it will take from the engine, and the more like it is to be sucked back during the overlap period of the cam. So be carefull here.



You can wrap the turbo exhaust scroll, but I would still be leary of it under an engine hatch.
But as far a the exhaust system itself, none of it should be uncooled.
again, this all pertains to closed engine compartments. In open compartment, with no rear passagers, you gain a little leeway. Unchained runs some dry headers to his turbos, and there is this deal:




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Discussion Starter #6 (Edited)
Well, it took me talking to you guys and some good friends whose expertise I truly respect to realize what needs to happen. I will be modifying my turbine housing by building a steel water jacket around it. I will build a double wall y-pipe to run from the risers to the turbine housing and then a double wall downpipe which will mix the water into the exh stream about 2ft away from the turbo.

What I need to know is the best risers fror the money. I can't use the stock cast risers b/c there is no way to separate the water and keep it out of the turbo. I guess maybe I can build some, but I'd rather buy a set and modify them if need be. No sense reinventing the wheel I always say. Something like these:



I have seen some stainless ones, too, but I want to spend as little as possible on them esp if I have to modify them anyway.

I will be running a dual exhaust from the turbo out thru the transom. I assume the water in the exh takes up pipe volume, so as not to increase backpressure, a big 4" pipe, no less? I'll be tuning the engine with a wide-band O2, so it will be in the downpipe before the water comes in, probably right up next to the turbine housing.

I still have not decided if I will intercool between the turbo and intake. The Gal Banks TT kit was intercooled, but I have always heard you can;t intercool a draw-thru b/c the gas in the intercooler will condense out and cause mixture issues.
 

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Ok, I am seriously-Newbie at boats. But, I have been building hi-perf cars for over 20 years. Don't laugh too hard if what I propose is so ridiculously stupid, just slap me and set me straight!

So, I bought a 19' bow-rider ski boat project (floor, stringers, engine mounts, transom, I think this thing was "sunk" in someones driveway for 10 years!) I am in the process of redoing it all myself.

The engine and drive are perect! Not even a leaky valve cover, very very little hours. It's a 305/Alpha One combo, 205hp 2bbl. Not really a "Performance Boat"... yet! That's why I'm here!

So while its all out, me being a speed guy, I want to block off the exhaust and run thru the transom. To save the stern drive all that heat, and free up some horsepower. I was thinking of building my own exhaust (because I can) but, and here's the big Q, is it possible to run the exhaust without water? I also have a single draw-thru turbo setup from the old Pontiac Turbo Trans Am I was thinking of running on it. It is not a boat turbo, no water jackets. So am I going to burn the boat down and sink it? Or is there an alternative to water cooled exhaust (I was thinking of wraping everything double with header wrap).

Can it be done? I have a pair of Rams Horn manifolds I was going to wrap them in header wrap, turn them upside down and build my own up-pipes, Y- the two into the turbine housing and run a single downpipe with a 6" riser and out thru the transom. The turbo should be good for 350hp on 10psi.

Next Q, can I run a closed cooling system and ditch all the hoses and other crap, just run a single radiator/electric fans or lake water heat exchanger? Again, be easy on me, I am a car guy, I have my car ideas, maybe they will work or maybe not. What say you all?

Thanks for your time guys.
You may want to look around. Gale Banks made a bolt on system for the Mercruiser 260 engine (350 cu in) that was able to be installed while the engine was in the boat, on top of the stock Merc cast iron exhausts. There was one for sale on here not long ago,, pretty cheap if I recall. I think I have some parts in a box that were from one of his early Merc systems, don't recall if there are the "wedges" in the box that went on top of the cast iron exhaust or not.
 

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You may want to look around. Gale Banks made a bolt on system for the Mercruiser 260 engine (350 cu in) that was able to be installed while the engine was in the boat, on top of the stock Merc cast iron exhausts. There was one for sale on here not long ago,, pretty cheap if I recall. I think I have some parts in a box that were from one of his early Merc systems, don't recall if there are the "wedges" in the box that went on top of the cast iron exhaust or not.
Here it is. You'll need a set of Mercruiser manifolds or make your own to fit. But for $700, this would be hard to duplicate.

LINK: Banks turbo set up for SBC Mercruiser



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One of those deals was on e-bay within the last 2 weeks.
 

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Seems like a lot of work for 350 hp...probably easier ways to make it and do it with fewer issues with heat.
 

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Dreaming is cool, we all do that, but reality is a little different.

Build a cheap 350hp 350 as chances are it's probably all that boat can handle. This will put most lightweight 18-20ft boats with Alpha drive at 65-68mph. Vortec heads, hot cam, and those cheap (but effective) Dennis Moore exhaust manifolds found on E-bay. Done. :D

BTW: most of us have come from car backrounds too. Getting into boats is a little humbling. We've all been there and we all thought thought we could get around the exhaust deal easily. DO a bunch of reading and searches and you'll get up to speed halway quickly.

Have fun with the boat ! Being out on the water (safely) is magic medicine.
 

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Discussion Starter #13 (Edited)
I have been building custom turbo kits for 10 years. I have turbocharged everything from a Jeep 4cyl to a '66 Pontiac Catalina and a lot of daily drivers in between. The nice thing about turbos is running a stock cam and getting great gas mileage when cruising, something you cannot get away with when you build a 350hp 350. A turbocharged engine will actually get better gas mileage part throttle acceleration and cruise due to the engine working "less hard" to fill the cylinders past a not-wide-open throttle.

I appreciate all you guys jumping in here with advise! I'd like to see pics of the TT kit. I am guessing they mounted the turbos directly to the manifolds, which is something I had not thought of!

I have two of these turbos (I actually have about 6) they are off the old '80-'81 Turbo Trans Am. They are relatively small, but draw-thru a 4bbl Quadrajet. I am going to use two of them on my 465" Pontiac in my Suburban tow-rig.

For the boat, I plan to upgrade the turbo with a bigger turbine wheel and compressor wheel but use the stock housings for fast boost.

I'll use this forum to post pics and updates of the engine build. Check it out!
 
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