Big block v8 fuel issue

[dwelf]

I have a 1997 checkmate with a 502 big block. Carb 850 cfm Holley. I have been fighting a problem all, year and initially thought it was ignition. I now know for sure it is fuel. After running across the lake half an hour or so my boat just dies dead from 5k rpm. This only happens after a few longer runs. I let it sit an hour and it fires back up and runs fine, if I try to start it right away it runs like crap, it won't idle at all so I can't take it in to dock. This has been going on 4 months now. I took out anti syphon on top of gas tank for a few runs and it still did it so that is not it. I have the mechanical fuel pump on the bravo seawater pump. I just noticed the idiot previous owner plugged the vent line on that fuel pump, would that create vacuum over time and kill the boat? Doesn't that diaphragm need to breath? I know it's an over flow to the spark arrestor in case the diaphragm when hooked up correctly ruptures so you can see the gas. Any thoughts? A side not, I am running it back to the spark arrestor regardless but would love to know before I take it back out if there's a chance this may fix my problem.....thanks

 

[achris]

Re: Big block v8 fuel issue

That vent line needs to go into the carb port it was designed for, not the spark arrestor.. One thing, Merc stopped using Holley carbs in the 70s... And carbs on the big block in the mid 90s... So, is that carb a proper marine carb, or just an 'off-the-shelf' automotive one?

And so we can have a proper look at the fuel system, an engine serial number please.... Also, is this an inboard engine or a sterndrive?

Chris....

 

[dwelf]

Re: Big block v8 fuel issue

I have replaced a bunch of off the shelf stuff to marine like the distributor and msd ignition box, alternator, starter...lol the list goes on. This is a Built engine with aluminum heads, I don't think the serial number exists any more, I had to put a marine arrestor on it. It is an inboard but the Holley has jtubes. So marine? I really just need to know what capping that vent line could do after long hours of high rpm. If I ever met this guy it would not be a pleasant meeting but my fault and the marinas fault for not looking closer at the boat before buying

 

[achris]

Re: Big block v8 fuel issue

Ok.. I had a look at some pictures of a marine holley.. There appears to be a port for the vent tube (from the pump) on one side. As for the effects of plugging the hose... Not sure, but nothing good. Could it build enough pressure to stop the pump working? I think yes...

Chris......
I agree with you... Idiots who put non-marine parts (that affect safety) onto boat engines need to be strapped to said engine, and have it touched off....

 

[dwelf]

Re: Big block v8 fuel issue

I ordered a new fuel pump, there is a plugged vent on the side of the Holley and one on back. I will get it back to a safe boat for sure. I really am just anxious to get it on the water and see if this fixes my 4 month old problem. Thanks for your thoughts