All- I’ve been fighting this problem with my Blackhawk for a couple of months now and I’m looking for some thoughts from some of you that may have experienced this.
Background is that this boat has not seen a lot of activity in the last four or five years, so the usual suspects coming to mind. However, I am not as familiar with the big block Chevy is I am small block so I’m looking for maybe some new areas that might not have full experience in.
Generally, the boat seems to be limited to 3500 to 4000 RPM. I’ve done the trimming in the tabs on this boat and do see some difference, but I’m not seeing the full speed that it should be seeing. The engine is a 502 magnum. I’ve refreshed the fuel as much as possible, replaced the spin on filter and even put some seafoam and injector cleaner into the fuel system. It might be getting a little better, but I’m thinking there may be a filter somewhere that I’m not familiar with that maybe his plug? Any thoughts that come to mind? I was to i’ve refreshed the fuel as much as possible, replaced the spin on filter and even put some seafoam and injector cleaner into the fuel system. It might be getting a little better, but I’m thinking there may be a filter somewhere that I’m not familiar with that maybe his plug? Any thoughts that come to mind? Looking at some of the diagrams for this Gen V1 engine, looks like there is a fuel cooler down under the engine, but not sure if anything there could present a problem.

So I take it you have had the boat out again? What props are on it? 31”? What speed are you seeing at 4000?

I put some chevron fuel injection cleaner and some fresh fuel and after a few hours it did hit 78mph at about 4900 rpm.... so I suppose that’s probably close enough to target to assume the balance is due to a used (not new) Engine....will see how things develop with a few more tanks of fresh fuel...

You really should get those injectors out and cleaned/replaced. The quickest way to burn down one of these MPI set-ups is running with clogged/bad injectors. It’s a fairly easy job to do.

Reach out to oso member BUP. He can help you out with the injectors.

Story of my life!!

Agreed! Best money I’ve spent!

the cap, plug and wires look good. Plugs overall good. I did check compression and a few cylinders were around 140....but nothing really wrong.

Once i I know the overall operation of the engine is good (from a sensor/wiring, etc i plan to power up the engine (this winter). Nothing worse than carrying a problem into a new build. I suspect any overall speed concern or gap will go away afterwards!

yep, nothing has changed from original..

cleaning the injectors sounds like a good thing to do.... especially since the boat is running better each time I run it.

who is BUP

for or some reason this link did not work...I’ll try later on my desktop

Those are 1970’s prices. Now it’s B.O.A.T.T.

Thank you for the input..... I’ve decided I’ll just replace them. Any particular brand or outlet?