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Old 07-06-2019, 10:11 AM
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Default Speed limited Blackhawk

All- Iíve been fighting this problem with my Blackhawk for a couple of months now and Iím 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 Iím 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. Iíve done the trimming in the tabs on this boat and do see some difference, but Iím not seeing the full speed that it should be seeing. The engine is a 502 magnum. Iíve 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 Iím thinking there may be a filter somewhere that Iím not familiar with that maybe his plug? Any thoughts that come to mind? I was to iíve 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 Iím thinking there may be a filter somewhere that Iím 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.

Last edited by sandslot; 07-06-2019 at 10:13 AM.
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Old 07-06-2019, 04:07 PM
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Verify throttle rigging is getting the throttle blades all the way open.
Remove, clean and flow test the injectors. These engines will lay down and lean out with injectors that haven't been used much.

That's where I'd start.
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Old 07-06-2019, 05:04 PM
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Prop size? What did it usually run? This setup has performed properly in the past?
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Old 07-07-2019, 01:02 PM
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So I take it you have had the boat out again? What props are on it? 31Ē? What speed are you seeing at 4000?
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Old 07-08-2019, 08:00 AM
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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 thatís 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...
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Old 07-08-2019, 08:44 AM
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By rights, the fuel tank should have been drained and system flushed (4-5 years little use).. dirty fuel only creates bad burn and detonation.... and headaches.

What condition is your ignition system in - plugs, caps and wires? they will rob you rpm on top of the weak fuel
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Old 07-08-2019, 08:46 AM
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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. Itís a fairly easy job to do.

Reach out to oso member BUP. He can help you out with the injectors.
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Old 07-08-2019, 08:50 AM
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B.O.A.T = Bring out another thousand...starts the season for maintenance, then turns into the fuel bill
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Old 07-08-2019, 08:52 AM
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Originally Posted by speicher lane View Post
B.O.A.T = Bring out another thousand...starts the season for maintenance, then turns into the fuel bill
Story of my life!!
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Old 07-08-2019, 08:53 AM
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