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Old 3.5 K&B outboard setup help

Old 02-13-2009, 11:03 PM
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all8up
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Default Old 3.5 K&B outboard setup help

I have an old 3.5 k&b outboard I was wanting to try and run tomorrow. the weather forecast is lousy.... around 40, both water and air temp....
1. was wondering where I should start at for high speed mixture screw? (black carb).
2. should I block off the water partially as well?
motor is totally stock.. trying to piece this together for my 10 year old daughter... thanks for any help...
Old 02-13-2009, 11:27 PM
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Ron Olson
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Default RE: Old 3.5 K&B outboard setup help

I'd start the needle at around 4 turns or more out but that should help you to get it fired up.
As far as the water cooling, you might not need any at all but I'd rather have it restricted first. You should be able to use a wheel collar or maybe a zip tie to do that.
Old 02-14-2009, 12:23 AM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

thanks for the help, I see u are in Kalamazoo ... do u know a guy named Tom Wright? he is a very good friend of mine. We used to drag race together.... ( big outboards) thanks, Kerry
Old 02-14-2009, 12:48 AM
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Default RE: Old 3.5 K&B outboard setup help

Sorry, can't say that I do as this city is bigger than most people think. If he still races on the liquid 1/4 mile there is only one place that I know of nearby where they hold them, Riverside Park along the Grand River up in a Grand Rapids suburb, Comstock Park.
The only full-sized boat racer that I know was my divorce lawyer, he did offshore OB Cat's.
Old 02-14-2009, 08:10 AM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

He has a boat like this one, thought u may have seen it running around town..
this is my old raceboat, I need to sell, although still emotionally attached to it.....
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Old 02-14-2009, 08:01 PM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

OK, I took the boat out.. waited till it warmed up to a whopping 39 degrees!!! wouldnt' stay lit if I removed the glow igniter... So I wen home, added more nitro to get it to 50%, put an OS A3 plug in it, and it fired up and ran smooth... Launched it, and it took off better than I expected, (this is an old dumas 24" wood tunnel without pickeforks) and turned much better than I expected... spun out and the tail got wet and killed the engine.. wouldn't refire and I realized the new plug got burnt out prolly due to the water in the [email protected] so I will hopefully try again tomorrow.... has anyone ran one of these old dumas hulls? are they any good at all? thanks in advance.
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Old 02-14-2009, 08:11 PM
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Default RE: Old 3.5 K&B outboard setup help

one of the reason your plug went could very well be because its the wrong plug for the nitro %.

the A3 is a hot plug for nitro up to 25%.

what was your other plug?
also, once the engine starts keep the plug warmer on the plug for another 10 second or so specially in the colder weather and if running a colder plug, if the engine dies than the plug is no good.

Dan.
Old 02-14-2009, 08:17 PM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

the other plug is not marked, and came with the boat.. So I would say it is quite old... would an OS 8 be a better all around choice? What would be a good all around plug that would work with either 25 or 50%? thanks, Kerry
Old 02-14-2009, 08:26 PM
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Default RE: Old 3.5 K&B outboard setup help

an OS 8(standard all around plug), McCoy-9 (cold plug), K&B 1L (hot plug) and HP (cold plug), or a McCoy-8 (med cold plug).

Dan.
Old 02-14-2009, 11:57 PM
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Ron Olson
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Default RE: Old 3.5 K&B outboard setup help

Those are really vintage boats. The first one that I saw at a race was back in 1979. Back then it was a miracle if they finished a heat as they had a tendency of flipping over backwards.
Old 02-15-2009, 12:06 AM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

OK, thanks for the reply.. sounds like I got my work cut out for me... I will try a little negative trim... it seemed flighty just in the short time I had to see it go!!! I can always upgrade the hull if I can get the engine running smooth... Kerry
Old 02-15-2009, 12:12 AM
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Ron Olson
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Default RE: Old 3.5 K&B outboard setup help

You might want ot try sticking some lead weights under the nose of it to help keep it from blowing over.
Old 02-15-2009, 12:27 AM
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Default RE: Old 3.5 K&B outboard setup help

You can also try adding trim plates to the rear of the sponsons. They can easily be bent up in a vise out of some sheet metal or brass stock and used with the added nose weight that Ron mentioned. If you can keep the attitude of the hull straight by itself and not rely too much on motor tilt which will remove speed from the prop, you should be left with some pretty good top end with it.
Old 02-15-2009, 08:06 AM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

thanks for the ideas.. might be fun to play with.. the CG on this boat is right at 30 now, so who knows where it needs to be..

I thought about extending the sponsons forward since the whole boat is only 24 inches now, I could add another 4 or 5 inches to the sponsons, creating more nose wieght, and also perhaps better balance, and the ability to hang, and take a set...

the boat then may be able to run a little higher in the nose, reducing wetted surface. I have a feeling the way the boat is now, it may have to run fairly flat with a lot of wetted surface to stay on the water any length of time...

I know on the big boats, the 16 footer I have is a handful to drive, because it really won't take a nice set, and u have to constantly be trimming the engine.. whereas an 18-20 footer will take a set, and stay trimmed out much easier..

I also thought about cutting it up, and trying to turn it into a hydro, keeping the current length, and pushing everything forward..
any thoughts?
Old 02-15-2009, 12:56 PM
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Default RE: Old 3.5 K&B outboard setup help

From the pics looks like the cavitation plate is cut off. Dosn't that effect the perfomance?
Old 02-15-2009, 07:27 PM
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Default RE: Old 3.5 K&B outboard setup help

Yes, thats the way it came when I got it... I guess they did that to run a bigger prop.. it has a 442 that prolly wouldn't clear... I could add some material back on easy enough... The skeg is more of a concern to me, as it looks whittled on as well, and dosen't sit very deep below the prop.. Oh, and by the way, I've been meaning to ask what's the best way to lube the shaft?
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Old 02-15-2009, 07:36 PM
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Ron Olson
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Default RE: Old 3.5 K&B outboard setup help

That's the way that the skegs were way back then. I'm sort of guessing here but probably when they first came out, they related them more to full-sized outboards.
Old 03-06-2009, 04:30 AM
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Default RE: Old 3.5 K&B outboard setup help


ORIGINAL: all8up

Yes, thats the way it came when I got it... I guess they did that to run a bigger prop.. it has a 442 that prolly wouldn't clear... I could add some material back on easy enough... The skeg is more of a concern to me, as it looks whittled on as well, and dosen't sit very deep below the prop.. Oh, and by the way, I've been meaning to ask what's the best way to lube the shaft?
Your engine appears to have a "California Mod". See:

http://www.namba.com/content/library...h/2004/may.pdf

Bill
Old 03-08-2009, 06:04 PM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

thanks for the help, thats an interesting read... my motor has the Cal mod, including opening up the exhaust, but still has the stock fitting and line for tank pressure... and stock carb.... maybe I need more tank pressure for this to run properly.... the boat handles like a piece of plywood bolted to a motor.. not much technology in those days... thanks, Kerry
Old 03-09-2009, 10:56 PM
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Default RE: Old 3.5 K&B outboard setup help

His motor does not have the CAL mod. It appears the motor is from the 80's or earlier that used the short skeg lower. Someone cut the cav plate off (hence the water pick up pointing forward) and then just opened up the exhaust ports.. Bet it's a loud one!
Old 03-09-2009, 11:02 PM
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Ron Olson
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Default RE: Old 3.5 K&B outboard setup help

Mark is right about the so-called Cal mod as that used a K&B red carb on the end of a tuned pipe as an exhaust throttle. Yeah, weird setup.
Old 03-10-2009, 03:46 AM
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Default RE: Old 3.5 K&B outboard setup help

Actually the CAL mod was more for the reshaping of the skeg, adding the throttle exhaust slider and opening up the exhaust ports.. People then went to the pipe with a carb on the end. I reshape all my skegs to the example Jack Garcia shows has in the above link. My choice for throttle exhaust is the use of Gardner XXL setup.. Need to bring that back from the moth balls and fire it up again.


Best way to keep the shaft lubed is this. Take the lower apart and drill out a small hole to where the powerhead and lower meet. After cleaning it all out, reassemble the lower and powerhead. Using a small glue syringe, squeeze the lube into the drilled hole. Do this every run and the shaft will last. My prefrence is a 50/50 mix of 80/90 gear lube and 30w motor oil.
Old 03-11-2009, 03:41 PM
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Default RE: Old 3.5 K&B outboard setup help

Ob nut... you said it...bring back the Gardner xxl exhaust throttles!! ...and Lee Garcia's Mini Marine pipes too!!!
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Old 03-12-2009, 07:03 PM
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all8up
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Default RE: Old 3.5 K&B outboard setup help

but since the exhaust is opened up, and the exhaust line to pressure the tank is stock, wouldn't that cause a lack of fuel pressure?
Old 03-13-2009, 04:36 PM
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Default RE: Old 3.5 K&B outboard setup help

Hi All8up,I have not seen this forum for a long time{no computer},but I do have extensive experience with this boat so here goes.If you really wring this boat out, be on calm water little wind.It's a carefull balance between the engine kick back and weight in the cockpit with a strong motor. You have it right when it blows over in somewhat rough water or gusty conditions.Drill a hole in right sideof casting lower unit at drive shaft area about 1/16" in plastic tube too, use motorcycle chain lube in spray can. K&b red carb,open up exhaust opening{connect the dots},octura 440x 640x,make a balsa cowl. This boat will be too small and unstable to race when modified mho but is fast and fun for playing.I used to at will, make 180 turns on the left sponson only to the amazment of my fellow boat heads.It's been awhile,'89 the motor went on to a hydroplane,the boat a kids toy. Good luck Pat

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