Looking for a little more power

[Glenn and his VIP]

Hello, New to this board here... I was woundering if I could put a 5psi supercharger on my 4.3 deckboat without any modifactions to motor. Im looking for a way to get a little more speed without ripping out motor.<br />I have a stock 4.3, 4 brl. carb on a 1999 -215 (21'5") VIP Deckboat. I see that GM makes one for the 4.3 S/10 pu. will this work ? Im also looking into nitrous if not supercharger. I wouldnt be using it all the time, Dont want to hurt boat but do get tired of friends kicking my butt. <br />Thank you !

 

[mkast]

Re: Looking for a little more power

Take the money you earmarked for improvements to your boat, add your boat to it, and Buy a boat more to your liking. It'll be cheaper in the long run.

 

[Glenn and his VIP]

Re: Looking for a little more power

I knew you were going to say this... hehe I guess I asked for it ! only problem is I have 25,000.00 invested now, the boat I want is 45,000.00 and not going to happen. <br />Im not wanting 150 more hp here, just 149... HOw many hp would it take to get 10 mph faster ?<br />I think mine is 210 hp @ 38 mph, with ss prop. tuned for boat.

 

[mkast]

Re: Looking for a little more power

I'm just guessing, if you want 10 more mph, I think you'll need a V8.

 

[AaronG]

Re: Looking for a little more power

I have a similar boat(22' Harris Kayot Deckboat), only with a 250hp 5.7 LX. With a light load, I can reach about 51MPH. The boats pretty fast off the line and crusies really nice around 35MPH. <br /><br />Why don't you just save up and buy a V8? I'm sure its less than a supercharger. The Mercruiser Carbed 250Hp 5.7LX can be found fulley dressed online for around $5300. That's probably pretty similar to the cost of the blower

 

[mkast]

Re: Looking for a little more power

 

[mkast]

Re: Looking for a little more power

If I remember right, if you go with the V8, you'll have to change the gear ratio in the sterndrive.

 

[WillyBWright]

Re: Looking for a little more power

I can't imagine that the automotive blower would tolerate marine conditions. Those on the Verados have a lot of anticorrosion components that the automotive one just won't have. Nitrous would be nice, but motors blow up awfully easily. If you want a performance boat, buy a performance boat. Perf-out a deck boat? Kinda like pim-ping out a minivan. <br /><br />A few more relaistic ideas would be a nice stainless prop (I'd suggest a High-Five or Mirage), and there's a tube (78458A1) that replaces the exhaust bellows that would be a really cheap way to get a few more ponies. Thru-transom exhaust would also give a boost. Get Silent Choice and you can run quiet thru the drive or loud out the back. You might consider a marine carb delivering more CFM than the stock one. Jetting would be mostly a guessing game, but awfully close to that of a 5.7 smallblock. Keep an eye out for an Alpha-One SS drive. There isn't much performance stuff for a V-6, lotsa stuff for a smallblock V-8.

 

[olbuddyjack]

Re: Looking for a little more power

Blowers and turbos tend to make a bunch of cylinder heat, tough on pistons, you really have to watch for detonation.<br />Props and such may get you a little more but not ten mph.<br />By the time its all said and done youd be money ahead with the V8. Good power, more reliable. Theres just no replacement for displacement.<br />

Kinda like pim-ping out a minivan. <br />

Whats wrong wit dat? <br /><br />(89 Caravan 2.5 turbo )

 

[paulrfrancisco]

Re: Looking for a little more power

If I remember right, if you go with the V8, you'll have to change the gear ratio in the sterndrive.

Couldn't this be compensated for with a higher pitch prop? I can see if you went from a V8 to a V6 where you'd need to change to a lower gear ratio from the higher ratio that the V8 uses, but the V8 would easily spin the lower gears, and then make up for the additional "propshaft torque" with a higher pitch prop? I dont know, but it sounds logical...

 

[mkast]

Re: Looking for a little more power

The six uses a higher gear ratio than the V8. A 4 bamger uses a 1.98 to 1.

 

[KaGee]

Re: Looking for a little more power

Somebody once posted it takes a 10hp gain to add 1mph in speed. Don't know where that formula came from or how accurate it is.

 

[QC]

Re: Looking for a little more power

Originally posted by KaGee:<br /> Somebody once posted it takes a 10hp gain to add 1mph in speed.

I have heard that rule of thumb before too and think it is reasonable in the 20 footer range and below 60 MPH. Above there things get progressively worse.<br /><br />I saved the stuff below from a post here on 1/25/06. I forgot who it was. I have not tried playing with it, but whoever posted it seemed to have a sizable clue . . .<br /><br />Here's the way to calculate it: <br /><br />Drag is a function of the square of speed so take your old top speed, square it, then divide by the old HP. Take that number, multiply it by the new HP and then find the square root of the result.<br /><br />For instance:<br /><br />50 MPH top speed with 210 HP changing to 300 HP would be: <br /><br />50 squared=2500, 2500/210 = 11.904761, 11.904761*300=3571.4283, The square root of 3571.4283=59.7614<br /><br />The new top speed would be 59.7614 MPH assuming the new prop is exactly as efficient as the old prop and that the two engines were both accurately rated for power.

 

[Glenn and his VIP]

Re: Looking for a little more power

Im still listening ! Im very happy with the boat now. Just want that "toy" if and when I need it, if it was upto my wife, it would only go 20 mph.. hehe Dont yell @ me here but...... what cha think if I put a 50hp shoot of NOS on it ?<br />Please dont yell @ me. Would 50 hurt it ? Remember its a big V6. Thanks again for all your reply's !

 

[vipzach]

Re: Looking for a little more power

Just do it Glenn, if the motor blows then the wife has to let you get the V8!

 

[QC]

Re: Looking for a little more power

Nobody's yellin', we want you to come back <br /><br />It's just that this is a very common theme and the right answers are all expensive. Most here will say do what you want, and let us know when you need help putting it back together. I would say that if you are really careful and know how to do things in moderation, rock on. The fact is that there is little to no data for any of us to rely on concerning Nitrous, so we err on the side of caution. If you really want to try nitrous, I would look into systems for 4.3 S10s etc on some of the vehicle sites. I imagine there is a lot of info and stuff from the street racer truck guys. My guess with your plan is that the weak link will be head gaskets. Oh, oh and how do you plan on dealing with the propeller issue? One for use with nitrous and one without? 10 MPH more is gonna take a lot of R's with your existing prop . . . if you use the existing prop floating valves sounds likely . . . <br /><br />Edit: BTW, what is your WOT RPM now? I apologize if that's above but I didn't see with a quick look.

 

[Glenn and his VIP]

Re: Looking for a little more power

wide open , nice day, smooth water, no wind 4200 rpm's, I have a stainless steel prop. now. I got to try several props one weekend last year, found the best one for overall power and speed. I know there not the same but I bet you know what Im talking about. I went with a fast one verse power for pulling. Thanks again !

 

[QC]

Re: Looking for a little more power

If your tach is correct, then you could run some more RPM (400 - 600) with the existing prop and for short bursts you shouldn't have any valve issues. Still think the big risk is head gaskets then. Not advocating . . . How is your fire extinguisher?

 

[vipzach]

Re: Looking for a little more power

QC good question! <br /><br />Glenn, 4200 rpm is too low! What size prop is that? Has the boat had a good tune-up, timeing and everything dead on?

 

[Glenn and his VIP]

Re: Looking for a little more power

Tuned it up last year, new plugs and wires, run cleaner through it every winterizing. runs great, went to a smaller pitch prop but lost alot of speed and hit 5000 rpm's. Are you sugesting to try more props first ?<br />Fire extinguisher you say ? hmmmmmmmmm "haha"<br />Im really really thinking about the supercharger that the 4.3 S-10 pickup's have, 6psi=84hp.. I need to find spec's on my motor first, compresion and all first though. VIP wasnt any help except tring to sell me a 45,000.00 boat with a big block. Thanks again !