troffer88

Hi , I have a 96 nordic sprint 22 with gen V 454 mag ,44 hours on boat .I installed dana exhaust, edelbrock performer rpm, and a 800 mech BG mighty demon carb . first trip out motor would bog off idle and at 2700-3000 rpm called bg and they said check vacuum and replace power valve to one that is 2" lower than idle vacuum, did that , changed to 10.5 (largest available) vacuum was 15". Now with full trim wont turn more than 3000 rpm and when I come to a stop engine floods and dies. looked at carb when restarted and fuel is pouring out front bowl overflows.Float level is set at low line level at sight glass at idle but after i run it it gets completly full.
any Ideas' Excesive fuel pressure ? .Crap in seats? this is a brand new carb with a fuel filter installed.Great forum thanks for any help. ps Prop is Bravo 1 26p

BY U BOY

lower your fuel pressure and remove the floats to see if they are functioning the way they should. Keep us informed i just put a BG 825 on my 454 and would like to know if you have any other problems. Also if your pressure was to high its possible that you could have over powered the seats and needles.

articfriends

iTrader: (1)

You definately have a problem with front float/needle and seat or fuel pressure is too high. I would pull the front bowl (no big deal),carb is new,if you remove it gently the gaskets should be re-useable. Pull the needle and seat,clean/check for fouling/debris then set it holding the bowl upside down so bowl is slightly past 1/2 way pont then re-assemble,if it still leaks your fuel pressure is too high. There is a slight chance your new float could be junk but I doubt it,see if its full of fuel or if the new black plastic stuff if its soaked with fuel. 10.5 is awful high for a power valve in a boat,usually you want power valve to be closed at very light cruising and to open as vacuum drops,if its open all the time except idle it will seem real rich,Smitty

HARDCORE A/O

What By U Boy and Smitty said.
Another possibility is that the tang on the back of the float that pushes the needle into the seat is bent badly but that, along with dirty or stuck needle etc. would flood the float bowl. Are you sure it's not flooding? If not, the problem most likely would be that the boosters are being fed through a leak in the Power Valve circuit which feeds directly from the bottom of the float bowl, so even if float level is ok, you can still flood through the boosters. Likely causes: ruptured P/V diaphragm or bad or improperly seated P/V gasket. please note that it is very easy to improperly seat the P/V gasket and then tear it up when you screw it in (been there, done that!) When you install the P/valve you should hold it with the spring straight up and lower the metering block down onto it and make sure the gasket stays in its seat until its screwed in all the way. Put a little petroleum jelly on it as well so it comes back off easily. I don't think the original problem was the flooding or the P/V. I would put the stock 6.5 Hg P/V in it and tune the idle (yes idle) circuits because they can give you an off idle stumble / flat spot like you described. my 2 cents...
Check those things and let us know what you find out.

troffer88

I agree with you, the boat ran alot better power wise my first trip out when it had the factory 6.5 power valve but it did stumble. Now no stumble but i have these issues, The thing about the fuel pressure is it didnt do it before i removed the front float bowl to change power valve and it is not leaking past the overflows on the rear so iam leaning towards the crap in the seats. The fuel pump is the stock mercruiser pump which is supposed to be 3-7 psi so I would think it would be fine.Would this problem be costing 2000 rpm? Thanks Tim

articfriends

iTrader: (1)

You could easily lose 2000 rpms if you got the plugs wet and a few are fouled or if you have fuel pouring into the primary side of carb all the time. I would get the fuel issue resolved then change or check the plugs before trying to run it at wot,check your oil for fuel dilution too,you would hate to wash the cylinders or worse while testing it,Smitty