In line fuel pump or cam.

[bipolarbear]

I got kind of a 2 part question. I just rebuilt my mercruiser 2.5 and had it bored .030 over and had all the required machine work done on the block, head and crank. The machine shop pointed out that 2 of the lobes on the cam were worn down pretty good and offered a cam that they had on hand. Being a not so fast thinker I installed this cam without visually making sure they were the same and when I went to start the engine I had no fuel and discovered there was no lobe on the cam for the fuel pump so I put a in line electric fuel pump in between the tank and the carburetor and now I can't get the engine to idle it will only run above 1500 RPMs, the pump packaging said that it was rated for 4 and 6 cylinder carbureted engines. I thought at first it may be the cam but if it was the cam I should be able time it in so that it runs. Any ideas wether my idle problem is to low or to high fuel pressure or the cam?

 

[Fishermark]

Re: In line fuel pump or cam.

Welcome aboard!

First things first - there are some safety items that you need to make sure are done. Be sure to wire the power through an oil pressure switch. That will ensure the pump only runs when the engine is running. Do a search here and you will find some good info.

Secondly, I cannot imagine the pump would have anything to do with the fast idle. Too much pressure will simply overwhelm the needle valve and flood the engine. You ought to check the fuel pressure.

Then, I would certainly be talking to the machine shop about the cam they used. That would be a major issue with me if it were my boat.

 

[Don S]

Re: In line fuel pump or cam.

Sounds to me like they had a racing cam on hand and they are all so glad they got rid of that piece of junk. You may even be getting water in the cylinders at lower rpm. (That;s called reversion)
You need to get the right cam, it's just that simple.

 

[90stingray]

Re: In line fuel pump or cam.

Could the idle circuit in the carb be gummed up? But I agree... not having the correct parts is not helping the situation.

 

[bipolarbear]

Re: In line fuel pump or cam.

Thank you for the answers pretty much confirmed my thoughts new cam is in order. What else are winters for but getting ready for the next summer rather do it right then be a bobber waiting on seatow.