got another problem. dies at about 3000rpm

[suprasaltareaud]

Hi guys. im stuck again. I had the carby fixed because secondaries weren't opening. I thought that was the problem. When i WOT or try to it seems to be either flooding or starving of fuel. When i get to 3000rpm + - 500rpm it seems to struggle. It sounds like when u have a warm lawnmower and u put the choke on and it dies except the boat motor keeps running just wont go over 3500rpm and sounds like flooding or starving of fuel. Back off wot and its fine. Otherwise running beautiful. Didnt notice till now because i was still running the motor in after rebuild.
any advice appreciated as always.

Thanks

Jason

[chris young]

Are you sure the timing is good and the advance is working correctly?

[CJD]

I assume no back firing, either through the carb or exhaust? If no, then I suspect something in your secondary barrels. Something like no fuel supply to that bowl, or no accel pump...if it is vacuum secondaries then the spring set too loose.

If the carb checks out, then fuel pump would be next on my list to check. Or, if you have a gage available...tap the line and check this while you are working on the carb. Make sure the pressure doesn't drop below about 5psi...6psi preferred.

[suprasaltareaud]

I will double check the timing but it isnt backfiring or missing. I dumped the oil today as it was running in oil and ready to be changed and it had a very strong petrol smell. I will check pressure and fuel pump also. Thanks guys.

Will let you know what i find

[suprasaltareaud]

Well i ended up putting a nee fuel pump in. I went mechanical because the last one lasted 27 odd years (assuming the previous owner didnt change it) and i figured less electronics the less chance of potential problems moving forward. Problem fixed. I had the carby rebuilt 8 months ago and i could see the fuel going in and secondaries were opening so for $54AUD it made sense to try it. I guess it was partly working but losing pressure up high. Anyway i pulled it apart and it had a small tear in the diaphram. So i bought new one. Reshaped the pipe/hose from pump to carby because of course the pump outlet was in a different position and took it out. It finally is running beautifully again. After replacing 3 bend conrods, rebuilding transmission and replacing some of the floors, repairing the fuel tank i can go skiing. Shit, its nearly winter here. Oh well. Time for the dry suit. Yeeeeeha.

[suprasaltareaud]

P.s. thank you all for your input and advice. I couldnt have got through all these headaches without you all. Anytime i can return the favour. Cheers. Jason