This is what is going on Last season I had a 25' vee bottom 440CI BBC and it had a B&M 174 on it. We also had a 750 holley on top. The cam was a Crane 226/236. The first time we ran it would only pull 4200 RPM. She would run strong to 4200 RPM. I could have a boat load. 4200 RPM I could change the props 4200 RPM. It had 3/8 fuel line and a Holley Red on it. I put a 1050 Holley on it and it only pulled 4200 RPM. Full tank and on E 4200 RPM. The Timing Is 8 degrees initial and 32 total.

Well this year I have a 24 foot HTM cat which is a better 454 With a B&M 250 1000 HP carb Lunati 224/234 the jetting was 82 front 88 in back. Today we ran it and She would pull 4500 and stop. We blew out a 29 Hydromotive it would not let the cat on plain. It would get to 3500 and blow out. The only prop the was left was a 22 Bravo from the old set up. 4500 is all she would pull. This was at 6 pounds boost. She is a fire ball out of the hole. Runs real hard to 4500. It has a holley blue with reg on it. The plugs read lean also. I was told today about tapping the metering block and running a vacuum line to the intake. For a distributor we are running an AC Delco with an MSD coil. Please answer the following:

1. What should be the ball for the jetting?
2. What should the timing be set at?
3. Should I block the power valve?
4. Should I run an MSD set up?
5. Do I need to change the pump to an Holley Black?
6. Since this carb is not set up for a blower will I have to run the vacuum line ASAP?

You should get a lot of replies on this, here is just one and an opinion. You can search previous thread on boost referencing, fuel pressure, jetting etc. and probably come up with a fairly reasonable amount of information as to what you should do. Just remember though, the decisions you make have a little more consequence than picking a sealant or wheel bearing grease.

Until you sort out exactly what your combination of cam, exhaust, hull weight, water temp, water pressure, fuel pressure, head design, oil temp etc. needs you are risking a meltdown. In my uneducated opinion I suspect with the jets you have and all the other variables unknown your combination may be risking a meltdown. With a blower motor you only get one or two chance to get it wrong. When you are in boost and carbueration or other critical engine conditions are not correct the oily parts and clean parts tend to trade places.

You can probably search the posts and get a good idea where to start and what to look for. Having been down this road before I would recommend you contact Nickerson Performance and give him all your particulars. I sent my carb to Dean and when I got it back all I had to do was set the idle stop. Plugs were perfect through all RPM ranges, good idle and not black transom. He has set up hundreds of these for the B&M and knows what works. There are others you may try as well that may be suggested. I am just telling you what worked for me.

Tim T.

I agree with BadDog, give Nickerson a call. He is the best out there IMHO

Kurt

http://www.nickersonperformance.com/

A larger carb may help. I've got 502's with B&M 250's, single 1050 on each motor.

Don't take chances on running lean and burning down the motor. Nickerson will get you set up and it will be right!!!!

Those jet numbers sound like what you would use N/A. Be very careful you don't run hard while lean. Is that distributer a Delco Hei? They tend to lose voltage over 4500 rpm and the advance curve is not performance oriented. A MSD dist. would be a good investment.

Timing. if you are using a merc ignition module be sure to use the 16 degree module from a V6 merc. It is recommended to have no more than 30 degrees total timing.

Last season a friend of mine had his fuel tanks changed. when he got the boat back it wouldnt go past 4500 rpm and was running leal. What he found was that his pickup tubes in the tank were to small and starving the engine for fuel.

In my opinion a 3/8 fuel line is kind of small for a blower motor of that size and hp

do you have a fuel pressure gauge??? If not get one. I feel it is a must on any blower motor. I like the Gaffrig one with the low pressure light built in. It saved me a few times. Low fuel pressure will create a lean condition. If the motor runs lean for a short while at WOT you could lose an engine.

If you loose fuel pressure at high rpm then it is your fuel system. Try and keep a constant 7-8 psi.