Mercruiser 454 Mag / EFI 385 HP KNOCKING NOISE
05-12-2015, 06:42 AM
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05-12-2015, 08:35 AM
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#1411-16 pictured here:
http://www.go-fast.com/boat_speed_predictions.htm
Last edited by man-of-war; 05-12-2015 at 08:56 AM.
05-12-2015, 09:53 AM
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Man of War, I wish it was that easy to eke out that last 5 MPH that you are after! Unfortunately, we are dealing with hydrodynamics, and not aerodynamics. Therefore, every extra 5 mph takes exponentially more HP than the 5 mph you gained previously. It's a lot easier to go from 65 to 70 MPH than it is to go from 70 to 75 MPH. I'm not a pro engine builder, but IMO it's going to take more than a slightly hotter cam, a set of roller tip rocker arms, and the likely required ECM remapping for your EFI to get that extra 5 MPH. I hope you prove us wrong, but I think you are going to find that it is a lot more involved and expensive than you first realized. Like I said before, marine high performance is a very slippery slope. 
BTW - do you have a link to a thread documenting the hull modifications that you made to that boat? I love what you've done with it. I actually have an old picture of it saved off back when it had a roots blower on it. Did you own it back then?
BTW - do you have a link to a thread documenting the hull modifications that you made to that boat? I love what you've done with it. I actually have an old picture of it saved off back when it had a roots blower on it. Did you own it back then?
07-30-2015, 07:43 AM
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I cut open the oil filter and found minor metal dust in the filter traped along the wall where the magnet held it. The actual cardboard filter had nothing on it.
I removed 6Liters of oil from the engine not sure if I should go with what the dipstick says or the reccomended 6.6Liters Mercruiser says this engine should take. I went with 6.6Liters and took the boat out for a run to see if the knocking and lack of power would improve,the engine sounds a little quiter and would run good for 10min or so but starts loosing power very slowly. If I let it idle and tale off again it would run fine but start loosing power again.
I was looking in on buying another 385 HP 454 MAG like the one I have with 200 hours on it but the heads were redone and had one hour run time on the floor.
The seller told me the heads were redone due to a tapping noise and the problem was a valve being sucked,not sure what that means but I think I should do a leak down test on my engine just to make sure the heads are ok.
HERE ARE SOME PICTURES
I removed 6Liters of oil from the engine not sure if I should go with what the dipstick says or the reccomended 6.6Liters Mercruiser says this engine should take. I went with 6.6Liters and took the boat out for a run to see if the knocking and lack of power would improve,the engine sounds a little quiter and would run good for 10min or so but starts loosing power very slowly. If I let it idle and tale off again it would run fine but start loosing power again.
I was looking in on buying another 385 HP 454 MAG like the one I have with 200 hours on it but the heads were redone and had one hour run time on the floor.
The seller told me the heads were redone due to a tapping noise and the problem was a valve being sucked,not sure what that means but I think I should do a leak down test on my engine just to make sure the heads are ok.
HERE ARE SOME PICTURES
