Got her better, but still need help

[Donziweasel]

Got some more feedback today from the boat. After having family here for 10 days, I was ready to sit on the couch, but my wife was having a cow about going to the lake, even though the Donzi was not running right. I couldn't take it anymore and headed up to the lake.

The only change I made was that I increased my idle from 600 rpm's to 800 rpm's. I has messed with the idle mixture screws and to simply set them for a days cruise, I turned them all the way in then 1 1/2 turns out each. Boat started and idled fine, so I left them knowing I would dial them in later. The boat still hesitated and bogged on planing, but not as bad and "caught" up quicker. A couple of times, no hesitation or bog, but still did not feel liek full power. Air temp was about 6 degrees cooler than previous runs and I was at a lake 1800 feet higher than all my other testing.

Any ideas on where to go from here? What in my setup chaged that the problem was a little better? Wanted to take some vacuum readings, but wife wanted to cruise. I will try and get some next week.

[Carl C]

Maybe a power valve that opens at lower vacuum. High capacity acc. pumps are available too.

[Cuda]

What carb?

[Carl C]

What carb? I think Dw went to a holley mech sec. carb. Maybe a double pumper. After thinking about this it seems like you'd be running rich if anything at altitude. I would check the plugs and talk to other folks running at your altitude.:confused:

[drew0982]

have u tried cleaning / synching the carbs?

[mrfixxall]

power valve,,,,,,,,,,,,,,,,,,,,,,,5.5 for starters

[Donziweasel]

Carb is Holley 4150 Marine with Mech Sec. It is brand new, so no cleaning should be required.

[Carl C]

I agree on the power valve since yours may not be opening soon enough. I've also found that holleys come a little rich because rich is better than lean. You may need to do some extensive carb tuning and I still think you need to talk to experienced high altitude boaters. You've already gained 9 mph, don't give up now! Good luck.

[mrfixxall]

D W you can elimiinatr your powervalve by putting a solid fitting in t he carb that holly sells,,but you have to jet up 6 to 10 jet sizes.....

[BigGrizzly]

I am with Mrfixall- don't give up your getting better

[maddad]

Randy, are you saying the power valve is unnecessary in a boat? Because of the steady load to RPM ratio? Just trying to figure this one out.

[BigGrizzly]

No, but it will work. I don't have one in my criterion for two reasons, 1 it is too hard to tune around on some motors ans 2 with the blower and a carb in a box it is always pressurized and doesn't work the way it was designed. I won't argue this point it is a fact on that engine. In the past when setting up some cars and designing cams we would remove them and jet normally. This takes another variable out of the jetting cycle. In fact one of the carbs I have for the Corsican doesn't have one and uses much larger jets in all four corners. The only problem is on some hot days it is a little contrary when cold. otherwise you can't tell the difference. bear in mind this carb is a double pumper and jet for each throat. If you have a metering block it doesn't work. when we were road racing we would delete it. Come to think of it I didn't have one in my gasser either. One thing it does do is compensate for altitude and really cold days. Just think of it as an enriching devise. Now you got me thinking I really liked the boat ran with that carb, now I need to go find it.

[maddad]

Thanks for helping to clear that up. I knew why they are there, it never occured to me that because a boat is never at part throttle/high vaccum/low load, you don't need one to transition out of that.
All I seem to learn is how much I don't know.