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454 Mag MPI limits to 4100rpms lost 8mph too!
Two months ago I was hitting the rev limiter easily, I haven't pushed the boat very hard at all, the last two weeks it's been limiting at 4100 mph, and I lost 8 mph. Nothing has been changed in the last two months. Seems a "lil" slugish, actually it's drives just like when I had my 3 blade out of the hole. Rams right up to 5100 when not in gear. I checked for off vacuum hoses and all plugs look good. Could it be a injector issue?
1998 454 MPI MAG 300HRS 24 hydro QIV 4800lbs |
Doe sit actually feel like its hitting the rev limiter???? or just doesn't have the power to pull past 4100rpms????
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I can't really tell, there is no mis-firing, nothing else seems to be wrong, the fuel pump is 1 yrs old, so I don't think that is the issue. It just climbs up and hits a wall.
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The rev limiter feels like a constant miss. You would definately feel it.
I would just do a basic tune up or at least start by changing the fuel filter and inspecting everything else. Also, check the timing. |
Nah, this feels like everything is perfect but just won't go above 4100, and it's ALWAYS 4100. I figured if it was a partial clogged injector, it would skip around a lil bit, but it doesn't.
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4100mph is fukin flying man....how much faster you need to go?
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Originally Posted by Shorgasm
(Post 3182999)
4100mph is fukin flying man....how much faster you need to go?
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I'm still having the same issue, I am stuck, I ramp up to 4100rpms and it just sits there, I'm stuck at around 57-58mph.
Beginning of the season I was hitting 5200rpms and 63-64mph. Here is the break down: Leak Down Test: good Compression Test: good Injectors working: good Injectors getting volt: good ECM: good Plugs (brand new): good Cap/Rotor (brand new): good Throttle body opening: good All wires to correct cylinders on cap: good Fuel Pressure: Good Could it be my drive? I don't know where else to look! This SUXS X 10!!! |
Check the fuel pressure.
Its not going to be the drive. |
I forgot to add that, but yes it's good.
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what fuel pump are you running? just went thru this.. mark
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Originally Posted by mookymonkey
(Post 3193801)
what fuel pump are you running? just went thru this.. mark
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Do you keep the boat in the water, or on a lift, or on a trailer?
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Originally Posted by 32storm
(Post 3194252)
Do you keep the boat in the water, or on a lift, or on a trailer?
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I'm still stuck, I don't know what to do next! :hothead:
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The heat kills horsepower big difference now from that cool air in the spring or earlier. Have you pulled plug wires one at at a time while running? Bad wire, plug or crossed.
The heat will knock you speed down in Dallas close to what you are seeing 63 to 57mph. Check for stow-a-way strippers from party cove, could be extra weight in the cabin. Several will ad up! |
Originally Posted by Texaswater
(Post 3196749)
The heat kills horsepower big difference now from that cool air in the spring or earlier. Have you pulled plug wires one at at a time while running? Bad wire, plug or crossed.
The heat will knock you speed down in Dallas close to what you are seeing 63 to 57mph. Check for stow-a-way strippers from party cove, could be extra weight in the cabin. Several will ad up! I purposely stay away from party cove just for that reason, having strippers on my boat is gonna cause a LOT more problems than losing mphs! :drink: |
Did you run the engine at idle and pull one wire off at a time and listen for an engine change? Trying to be sure you understand that test.
I see you have NEW plugs Did you use NGK's they work best with high energy ignitions (according to Mercruiser) Important to Check the cabin! You Close one eye anywhere on that lake and Strippers will move in fast! |
Also,
How about your battery? Is it a good high Amp battery? Really effects the ignition. My guess ignition plugs wires or battery amps. Along with 110 degree weather. Non NGK's will appear good but break down with this engine. No miss just won't run up with a load (in gear). Good Luck! |
I purchased a new Hydromotive 23p QIV in April, I must have been smoking a LOT of crack that day, because I swear I hit the rev limiter with the new prop. But that is not the case. My whole problem had nothing to do with my engine, it was simply going from a 23p Mirage Plus 3 blade to the 4 blade Hydro. The loss of the MPH was due to the outside temperature of 105 degrees and the lake temp of 96 degrees. Friday I purchased a used 23P Mirage Plus 3 blade, I took her out today, 75 degrees, 77 water temp, bam, 5000 rpm, 62mph.
I did learn that the Mirage Plus 23p is not a true 23, but more like a 21 3/4p and I should went with a 22p Hydro since they are true to size. I did learn quite a bit about my engine, specifically it's running perfectly. |
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