Fuel feed issues
 

OK I believe my new 509 is have some fuel feed issues. It really feels like power falls off on the big end and I have no top end. This motor dynod at 684hp and compression is 165 across the board. I expected to see around 95 mph at 6250rpm with 28 pitch and 1.5 drive...I am no where near that. It wouldnt wind past 5500, put a 26 pitch on and it got worse, couldnt wind even 5000. Performance seems to be diminishing.

My first thought was fuel pump, pulled the pump and there was some fuel in the pulley driven water pump reservoir cam mechanism. I put on another pump but have not tested it. I will tonight.

I dumped the separator out and there was a lot of debris in it. Could any of the debris make it to the carb through my filter water separator? There was no water in it but my mechanic friend said it didnt smell fresh.

What are the possibilities of the screens on the pickups in the tanks being plugged?

Coming from fuel injection here and do not have much carb experience. there is a mechanical gauge on the carb feed line and I am installing a sender to get my gauge working tonight. Last I knew it was at 6psi idle and 4psi under load, is that acceptable?

I am going to drain the fuel tonight and see what it looks like.

Thanks for the help.

Is this the same fuel pump that it was dyno'd with, from your explanation it sounds like a stock merc pump driven off the cam lobe, your under load psi reading sounds low to me.

That seems a little low for your application. I'd rather see 7 to 9 psi.

I think you're on the right track looking at the pump. You will grenade that monster if it's too lean.

It was dynod with an electric and a regulator I believe.

That may be the issue, that stock pump was not made to support the HP that your running, I think if you install a good electric marine pump and regulator you will see a big difference

I agree.

What size lines?

I would have to look. I think the smallest line would be the hard line from the pump to the separator.

I'd run -10 to the pump and minimum -8 after the pump. Volume is the key. 6-7psi will support plenty of power carbed if the volume is there .

I know for a fact the lines are not that size. I think the hoses are 1/2" to the pump and the hard line after is maybe 3/8".