High End Performance

Is that what you call a "twin Boob-balist" system! It will make a wake sooo big you wont even need a rope!!!!!!

Hey! That's my wife!!!!!!!!!! Where did you get that picture?

Here's a summary of last nights run.

Timing - Perfect
Throttle cable - Perfect (minor adj. by Tim)

Tim and Brad put there minds together as we went from a quick 600 RPMs, up to 4,800 RPMs. We stayed at about 4,800 RPMs for about five seconds max and the engine RPMs dropped on their own to 4,100.

Tim and Brad were confident the float in the secondary is out of adjustment. They bent something in the float and put it back together. We saw a 200 RPM increase and it stayed in the higher RPM band longer before backing down. We then ran out of light, so we packed it in.

Does anyone know of a way to judge the distance of the float adjustment to get it right on? We still have some work to do.

Here's a video from last night, thanks to Brad's new video camera. Listen closely to the RPM's. Can you tell when it drops?

Engine RPMs dropping

Ken

It should be pretty obvious from the video when the rear bowl runs out of fuel- Ken isnt backing off the throttle and it slowly drops from about 4800 to 4200 RPM.

The secondaries appear to be functioning properly- they come in at the right time and stay open (even when the RPM's decrease). No stumbling or other driveability problems. If you back off on the throttle and give the rear bowl a little time to fill, the motor will achieve a higher RPM when you go back to WOT (until it runs out again).

Like Ken said, the timing is fine (advances from 6 degrees at idle to about 27 degrees at 3000 RPM). Throttle cable is getting full range. It just wont hold 4800 RPM.

We raised the rear float level and it appears to have improved performance. Ken said that sustained WOT RPM's increased from 3900 to 4200 with the float adjustment, so it appears we're on the right track. We didnt have a scientific way to adjust the float- just bending the arm a little at a time and using trial and error.

Im also wondering if it could still be a fuel pressure issue. Is there an easy way to measure in-line pressure with the hard fuel line?

Any other thoughts?

Edit: Im too slow with my reply. Chris, did you watch the video? It performs great out of the hole and at WOT until the rear bowl runs dry. Not sure where that float should be adjusted- does it look like it should be raised more or is it more likely a fuel pressure problem? Maybe we need more info to tell.

I should also thank ReidP and his buddy Todd for their help on the phone last night!

Chris,

I haven't checked the check valve in the fuel line. Good idea.

Page 49 of the PCM service manual indicates that a specific toll is necessary for the adjustment to the float, Kent-Moore J10193. I Googled, carburetor adjustment tools. Here's one site I found Tools.

Tim, I'll give Vincent a call at SKIDIM. Maybe we can check the check valve in the line too?

screw the tool raise it a little more bye sight if you go too much then bend it back slightly.

or you might need to raise the primary float slightly as well.

won't the primary float control weather or not fuel is entering the carb before the secondary even comes into play?

I tend to agree with the stavation problem, float adjustment is important but if it was as touchy as you guys are making it seem this thing would never make it around a corner. This boat is running like a boat that has been sleeping too long too often and has crud in the system.

One more question, would the pitch of the prop have an effect on top end? Maybe it bites in better after plaining and loses RPM. Should I slap on the factory 13X13 to see what happens?

Ken

Got ya. What do you think of Correct Craft's idea with filling an O/B motor gas tank and running the fuel line directly to that?

Ken

Nautique2001 wrote: Got ya. What do you think of Correct Craft's idea with filling an O/B motor gas tank and running the fuel line directly to that? Ken

waiste of time if it was fuel starvation issue you would never see the top rpm to start with. Change the timing raise the float and be done with it.

Nautique2001 wrote: The fuel tank was inspected a year ago for crap and sediment. It's clean. New fuel hoses and filters.

Was this another NECC job, Ken?

I wouldnt say we're nitpicking, Chris- just trying to narrow down the problem. I agree that the timing is low, but it starts and idles well, advances properly and gets the boat to 4800 RPM. The secondaries are obviously starving at sustained WOT running- could that be caused by a 20-30% decrease in flow to the pump? The secondaries are initally fine as you can see in the video- its just that the bowl empties faster than it can refill. Im certainly not ruling out the float adjustment, just saying it may not be the only thing to look at.

If you're getting 4800 rpm what is the problem??? Or is this a typo and supposed to be 3800, else I am very confused.

Hollywood wrote: If you're getting 4800 rpm what is the problem??? Or is this a typo and supposed to be 3800, else I am very confused.

Chris gets it. If you watch the video, you can see/hear how the boat gets up and goes very well. It gets to about 4800 RPM before it slowly starts to come back down (around the 15 second mark) and finally settles at 4200. Ken stays at WOT in the video up until you see him pull back (just past the 1 min mark).