383 dyno success!

[HT32BSX115]

Re: 383 dyno success!

Yes this is a pretty good thread!! Sometimes it IS good to resurrect old threads!!

Here is a few picks of the check ball. There can't be much flow past it. all is does is keep fuel from running back into the tank.

This is a common misconception of why the "Anti-Siphon" valve is there.


The answer is in the name though.... "Anti-siphon" It is NOT an Anti-drain back valve. (although it could do that) It's not there to prevent fuel from draining back into the tank!

It's there to prevent fuel from SIPHONING.... out of the tank.... and into the engine compartment..... (Some times Kaboom results!!!)


USCG regs REQUIRES them on boats that have a fuel tank (actual fuel level) that is physically higher than the lowest part of the fuel supply line...... to prevent fuel from SIPHONING out of the tank in the event of a leak at the lowest place in the fuel supply line.

There's alternatives, you can use an electrically operated fuel valve that will shut off when de-powered. (Boatmakers would rather comply with the reg using a $5 check-valve instead of a relatively expensive electrical solenoid operated valve and associated circuitry)

If you think the anti-siphon valve is causing a problem, just put a fuel pressure gage on the carb. If the (WOT) pressure is staying above what ever your minimum should be, the the anti-siphon check valve is NOT restricting flow enough to be problem.



Cheers,


Rick

 

[JHuck]

Re: 383 dyno success!

Reality is what you make it!

Ain't nothing wrong with using a Blower,

IF,

You do it right.

I've run this one 30 years, so far. but it is not on my boat.
Well, I guess this old browser is not going to let me attach a jpeg. Must be cause I'm still running Win98 on this box and can't install any updated browser. lol.
I have a straight 3 lobe Roots style Magnuson on my 79 Shovelhead, built during the Winter of 79, haven't grenaded it yet, and I turn it pretty hard sometimes well over 9 when I miss 3d gear.

If your thinking Blower, look into the Eaton twisted 4 lobe AND a serious raw water intercooler, guaranteed, it can be done safe, reliable, and surprisingly strong power addition, you WILL need to up-grade your drive even if you have added a 'drive cooler' sprayer.

Oh, I agree on the reality piece. I don't have concerns with the engine because I know it can handle more. My issue would be forking out some decent cash for a used Bravo lower and gimble.

 

[45Auto]

Re: 383 dyno success!

I guess I was thinking more of the guy who has a marginally powered boat and skis, so he under props which would put him way above peak horsepower but just controls it with his right hand . . . Examples like that. I used to rent Houseboats that were propped way low too . . . I think they did it as a cheap RPM limit

Hey QC, I think some of the confusion on the propping threads comes from terminology. For example, in your quote above you first talk about "under propping", meaning a lower pitched prop. In the last sentence where you talk about being propped "low", I know you're talking about "low" numerically (engine revs vs prop revs), which means a HIGHER pitched prop, but lots of people read that "low" as meaning lower pitch. In which case it makes no sense at all (lower pitch as an RPM limiter??) and I can see how it would confuse people ....

 

[JustJason]

Re: 383 dyno success!

I hate jumping in on high performance or go fast threads because they are usually so full of BS, and half the advice given in any of those threads if followed will usually lead to meltdown city.

Aside from that statement, i'll also say i'm no expert in the world of go fasts... heck, I don't want to be. Up here we have a fountain dealer and half the boats in his yard are all 2 or 3 years old, all with 2 or 300 hours, and they all have smoked engines with angry owners who don't seem to understand that 90% of wear and tear happen in that last 10% of the rpm range. And that if there are any actual mechancal problems (usually in the fuel system), the motors grenade in that last 10% of the rpm range as well. It's a headache to deal with, so I just stay out of it.

That being said, where do you prop your boat. I'll offer this bit of advice, and you can take it for what it's worth.
If you want reliability, and not that extra 1 or 2 MPH top end. You prop the boat light, just you in the boat, very little fuel, nothing extra but the essentials on board, no water if you have a water holding tank either. At that weight you prop it so your 2 or 3 hundred rpms shy of the actual peak HP rpms. So in other words, if your dyno shows peak HP at 5500 RPMS, you want to try and prop it for 52-5300. And if you can, you want to prop it on a cool dry day.

You want to prop any boat (unless your specifically trying to accomplish a specific task) so that if the throttle is hammered, the engine does not rev past it's peak HP where the power will drop, because if you do this is what happens.
1. Engine rev's past peak power
2. Power falls off, friction/drag starts taking over and the boat gets pulled back into the water.
3. Power can't keep up with friction, rpms fall, as the rpms are falling the engine is still pushing, or trying to push but does not have the power to. you now have lugging at this point. Lugging leads to increased combustion chamber temps, which leads to detonation, which leads to meltdown city. The biggest problem is you can't hear detonation at 5k rpms. Alot of times the knock sensor doesn't hear it to. Which is why even engines with a knock sensor still melt down.
4. RPMS fall enough that your now back into the high end of the powerband
5. Power starts climbing again, and the boat will now start to accellerate and push itself out of the water again, through the friction/drag of the water
6. It's a cycle, that will happen over and over if you prop it to hit actual peak HP RPMS, and you don't want to be in that cycle

Wether you have a mechanical rev limiter (the prop) or an ignition rev limiter, you don't want to be hitting it, just getting close to it.

That's it... that's all i got.

 

[QC]

Re: 383 dyno success!

I know you're talking about "low" numerically (engine revs vs prop revs), which means a HIGHER pitched prop, but lots of people read that "low" as meaning lower pitch. In which case it makes no sense at all (lower pitch as an RPM limiter??) and I can see how it would confuse people ....

Agreed, mixed terminology . . . bad. I was moving too fast. A couple of extra words should fix it.

 

[wca_tim]

Re: 383 dyno success!

Very nice. Any idea on hp? Does that put you in the mid-80 mph range?


In a moment of weakness, I looked at roots blowers this spring but then I came back to reality.

I put larger combustion chamber afr195s on it to drop the compression a little - with every intention of adding a blower. The bottom end is built for it and I was thinking it would put me around 550-600 horsepower at that point... more if I'd gone the procharger route.

I'm thinking someplace between 450 and 500 right now.

However, with the ss drive, a 26" 3 blade turbo and a light load, I was pushing 90 a few weeks ago.

Not sure I want to push this boat much faster... It's only 17 ft long... we already cruise at 55 or so just loping along. I also get a lot better fuel economy now... also added a different carb, intake, etc... without even getting into it hard, we easily walk away from about anything on the river (except the guys with the fast ie allison, stv, mirage, etc... outboard set-ups). on the river boarding and skiing 3-5 days a week now... and loving every minute of it. Enjoy!

 

[45Auto]

Re: 383 dyno success!

Hey Tim, thought about you for some reason when I saw the video on this thread ......

http://forums.iboats.com/showthread.php?t=411129