Blunt nose Hot Shot & K&B 3.5 with a slide throttle setup

[Les Laming]

I just purchased a blunt nose Dumas Hot shot with an older 3.5 K&B OB with a slide throttle that has never been run. I have run quite a few boats in the past. I do not race, I simply run for fun. The first owner modified the cowl and has the fuel tank in the front of the boat. I know that the engine won't draw fuel for 14" and it will need to be located near the transom. Did the first K&B' OB's run very well with the slide throttle. I have another K&B carb with a rotating throttle barrel that I can use. If I removed the throttle flapper and replaced the carb with the one with a rotating barrel hooked to the throttle cable would I have better idle,transition,and throttle control?

I plan to relocate the tank near the transom and have the radio in the middle of the boat. Where should the CG be on this boat? I was hoping this would be a simple project but the more I get into it the more complicated it becomes. Thanks for your help and feedback. .Les Laming

 

[Jerry Dunlap]

I would recommend replacing the slide throttle with the carb. I never had much luck with the slide throttle. It would often stick and not shut off the engine.

A typical CG for a tunnel boat is 1/3 the distance forward from the transom. Seems like the original Hot Shot was 24" so that would put the CB at 8".

Elevating the tank with a piece of foam will assist in fuel draw.

JD

 

[brad nichols]

The barrel is just better for this application some will argue that but you are referring to an exhaust throttle. Moving the tank and radio box is a good thing too, but I can't coment on balance point but someone will.

Happy boating

Brad

 

[Grimracer]

what a fun boat.. yes.. not much room in that boat for the tank.. just put it as far back as you can and as high as you can. 8" on the CG will get you rolling quite well. I have one (retired) that I ran a K+B SS on.. (Updated bottom).. the boat would take off like a frissbee at 40mph!..lol

Grim

 

[moparbarn]

When you remove the exhaust throttle, you will need an exhaust adapter to fill the gap between the power head & the lower unit's exhaust chamber. If you need one pm me your address, I have one I can give you for free. If you're outside the US, I ask that you pay shipping. JD & Grim are spot on with their suggestions (-;

 

[Les Laming]

Thanks to everyone. I can now begin my modifications. It will be about the middle of April before the lake changes from solid to liquid.I enjoy fixing up other people's problems. Les

 

[Grimracer]

Robin.. when it comes to the K+B.. the adaptor that comes with it is a good one.. as it goes.. if the old K+B leaks a tick in the exhaust.. that's NOT A BAD THING..

Want to see a 8907 run 50mph on a tunnel boat.. MAKE HER LEAK!

Grim

 

[moparbarn]

Les - got your pm, might be able to get it out today, tomorrow for sure. You don't owe me a penny, just pay it toward when you're able (-;

Grim, I hear ya! I've cut a notch/slot in those adapters, & prefer the early can muffler mounts with the hole. It does make a difference.

 

[SayMikey]

So does a bigger hole Jmo

 

[Les Laming]

The builder made a wooden cowl that runs from the cockpit area to the transom that has a floor in it. . The fuel line will only be about 3" long but the centerline of the tank will be about 3" below the carb. Does the motor need a hopper tank or will I be able to tap it for a pressure fitting? Will fuel draw be an issue. I have several other boats but they are running muffler pressure. So far I have shortened the fuel line about 12" . Thanks to all who have responded.Lastly I have a Perry carb that was made for the OB.Would you suggest using the Perry? Les