I seem to be having problem with top end, I'm only turning 7450 at best on a tripple pipe limited. After running for about 1-2 minutes the rpm's just keep slowely falling off down to 7000 rpm's. I have turned out the high speed screws which showed no difference. The egt's only show around 600 or so. I have zipped tied open the power valves to make sure they are opening, no difference. Changed pumps, no difference. The low and mid feel real strong but then it falls on its face on top end. I'm out of ideas what to look for and I have the first race next weekend, anybody have ideas other than sinking this bastard! Thanks

P.S. The entire engine and boat was rebuilt during the winter, everything is new.

Fred what are you using for an ignition and what is your compression #'s? Also did you pressure test the motor?

Hey FRED !! Check your pipes , Advent box.
Lots of variables , Looks like dean and I will be on site thursday , If you still need help this would be a great opportunity .
Call me tomarrow .
Gary

Deffinately check the pipes. I was having the same problem, but when I checked the pipes they were fine. Mine was doing the exact same thing.......only turning about 73-7400. I checked everything and couldnt find anything wrong. Finally it got to where it would hardly run at all.........thats when I found a crack about 6 inches long in the collector piece right before the water box.I went to 3 races this year before I found my problem. Good luck.

I did check the pipes before putting them in and I know they are ok. I'm using the Advent CDI, its the same one that I have been using the last 2 years except that I had a new timing curves put in this winter. I didn't pressure test the engine though, can I do that in the boat? and how do I do that? My compression is 175psi across all 3 cylinders. I guess I need to narrow the problem down, is it electrical or mechanical? Thanks to everyone for the suggestions.

Fast Fred

By any chance did you change or add anything to the motor just before this problem started?

Jason S one of the Island racing boys

is the jetting the same?
is the same exact untouched crank in the boat?
did you "vaccum test" the pipes making sure there is no internal crack, if your motor is only spinning 7400 and then creaps to 7000, and doesn't stick a piston, or foul a plug, I would start with the pipes. plug the pisser hole, and use a mighty vac to pull vaccum, your going to find a leak. otherwise swap the cdi?

been there, done that
henry

The motor was totaly rebuilt this winter: New crank, pistions, domes, new timing curve on the CDI. The boat has been giving me trouble from the first day I had it out this year, so its hard to determine one thing. I did do a pressure check on the pipes, I had 4 pipes crack on me last year so I'm pretty sure I know what to look for on that. I'm starting to think its the CDI unit, I might have access to somebody else's Advent CDI tommorow, I'll find out tonight. Other than that I'm not sure what else it could be, jetting is the same as last year too. Any other ideas to look for during tommorow's session? Thanks guys.

what carbs and jetting are you useing?--what method do you use to test your pipes? also the pipes you cracked in the past --wich ones cracked?

Jason S one of the Island Racing boys

48 Novis with 140 mains, 135 lows, 2.3 N/S 90 gram spring with 70 return jet. Always worked well in the past. To test the pipes I made a homemade hose thing that lets me pump air into the pipes with a inline guage to monitor air pressure drop. As for the pipes that cracked, 3 centers and 1 rear. I also sent the front one in this winter to FP to check it over, it was ok.

Better Grease your muffler bearing !!!

Here is a really simple suggestion, check the battery, dropping RPMs can be due to a week battery. Try replacing the battery with a new one and see if problem persists.

Fred wondering if you got it figured out yet or are you still chasing that Gremlin? If it is fixed what was the problem?

You might wanna open the power valve covers and check them out. I had the same problem and it looked like the valves were opening but when I took the covers off I found one of the little screws broke. It was the screw that you replace when you install the wave eater clips. If you dont have the clips........its the allen screw that you first see when you open the cover. Thats what my problem was. Good luck.