When you replaced your fuel filter, did you fill it COMPLETELY up with fuel? I've seen my 454 MPI be very cranky, and even not want to start and run, if there was ANY 'air' left in the filter. I always thought it would sort of self-purge by objective evidence indicates that isn't so.

I read on the forum that the CR43TS was a good alternative to the MR43T as it has a projected nose. Should I just stick with the MR43T? I tried to post the url but I don't have enough posts.

cr43ts ‘s are great on non vortec small and big block black engines.C= commercial )coating for less corrosion. Ts is projected tip. They don’t make the ts’s in marine. They do on regular r43ts and commercial cr43ts.

We typed at same fine. :) look above. They are Great plug :thumbs

I believe so, but I will check it again.

Bajaman makes a great point. The first year I had my 502 mag mpi, I fired it up to change oil and fuel filter for winterization. After changing, I fired the engine up, it ran for about 30 seconds and quit, could not get to keep running. Pulled the fuel filter back off and it wouldn’t fill up with fuel pump. Filled up to the top, made sure all air bubbles were out, put back on, and she fired right up. Do it every season and haven’t had a problem. I am not an engine guy, but my previous carb engine never had that problem......assumed the electric fuel pump would fill it? Not saying that is your problem, but a good thing to remember to do.

While waiting for fuel psi tests…..

He said engine runs fine until shut off again, so filter would be full while running. Filling filter is not his issue, but you guys made great point for all. Electric pumps will typically cavitate and not pull fuel when filter/separator not filled.

OP- does engine crank over fine or does it labor ? Are batteries fully charged and holding charge ? They should measure around 12.6 with engine not running and not charged for atleast few hrs.

https://cimg1.ibsrv.net/gimg/www.off...ce0de482e.jpeg

If its cranking slower then normal i'd be looking at getting the battery tested to make sure its up to par and then inspect the main batt cables for corrosion...

Consider looking at gas to see if you see any seperation or rust from tank. Really a 1998 boat probably at end of fuel system life. If not been done already I'd replace all the fuel lines.

Thanks for all of the replies so far. I have noticed that it seems to be cranking more slowly/labored than normal. I will put the batteries on the charger and see if that makes a difference. The battery cables look good, I recently installed a new battery switch and cleaned up any corrosion.

I should be able to check the fuel pressure this afternoon, the weather is finally clearing up.

Any ideas why the plugs are so black? Could that be related to this issue?