nothing_fancy

I was thinking about switching to a Holley red electric pump 67gph at 5 psi

nothing_fancy

Pulled the pump push rod and compared it to a305 and it's the same 5.75in rod and checked on summit racing that's what it should be. So is my new fuel pump junk or to small???

Shalom

iTrader: (2)

Since you are looking for all possibilities, here is a long shot....I once purchased a boat and had the same problem... The problem turned out to be that the marine fuel pump weep hole nipple tubing was hooked up to a vacuum port on the carb instead of being hooked up to the flame arrestor. So every time I would accelerate it would pull a vacuum on the top of the mechanical fuel pump diaphragm which resulted in weak fuel psi.. It made the motors run very lean causing what I call lean pops at 4000 rpm's. I could run it at 3000 rpm's but that was it until I put the tubing in the correct position.. Simple problem to fix if this is it....Good luck...r

nothing_fancy

The weep tube is on the nipple that dumps into the top of the secondary side of the carb where it should. So it's not receiving manifold vacuum

Mr Maine

It seems like you have ruled out everything but the pump. I would try another one if you can. My experience is mechanical is very reliable and simple I would stay mechanical for simplicity. My block is a 98 so its not drilled so I have an electric pump. Fwiw mine is a summit 95gpm and have never had any issues knock on teak

nothing_fancy

I would try another but I'm having trouble believing that both pumps I've got are bad. I'm thinking of going electric but if I don't have to ill save my money for some stainless risers. If it is the cam loab I really won't know till I pull the cam which I'm planing to do this winter anyway going bigger so maby the electric is the better route

FIXX

iTrader: (2)

Even tho the line is going to the flame arrestor make sure the flame arrestor is vary clean and is big enough for the engine..if the fins are cluttered with crap it can suck and act like a vacuume port..also get the mallory red marine electric fuel pump..the holly one sucks and is vary noisy if you do decide to go electric..me personally i hav a electric pump on my donzi and would not go with out one..

ThisIsLivin

You could get an indicator extension for a dial indicator and run it against the cam and turn the engine over by hand to see what the travel is. It's unusual to see 2 bad pumps with identical issues, unless you got them both from the same batch. Does your fuel distribution to your carb have an internal filter, that could be plugged?

nothing_fancy

Took out the carb filters that I installed when it was new a couple of months ago they were clean any how. Onto the pumps one was the original that came withe the boat when I bought it and then transferred to the new engine the second was bought a week ago. I'm starting to wonder if there is a reason that the smallest mechinal pump from Holley is110gph free flow. I'm going to try to get a pump only pressure to see if I can get the 5.5-6.5 the replacment pump is rated for, that should be a good indacator if its pump defect or lack of flow. If I do check the cam loab what should it measure at? This was a reman jasper and I don't know if they grind cams or not. And not to forget the spark arrester it is clean and I did a short run without it.

ezstriper

if not the pump would have to be the cam for the pump I would think..