Slow Hull; 100 more h.p. & no more mph
09-26-2002, 08:45 PM
#1
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Slow Hull; 100 more h.p. & no more mph
I have a 1997 Donzi 25ZX with a 502 mag on which I did a Tyler Crockett CAM Kit Upgrade. I increased my engine by 100hp and didn't see any gains in top end. Has anyone else tried to upgrade a 1997 Donzi 25zx with different results?
09-26-2002, 09:01 PM
#2
You may have only added the 100 HP at the top end and you dont have the HP to reach that higher HP level. You may have to change props to get into that level. Does your boat have any hook???
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09-26-2002, 09:36 PM
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I went through the same dissapointment earlier this year. I have a 20 ft Formula that I went from 205 hp to 330 hp. The top end went from 43 to 49 mph! WTF! 61% increase in hp, and 13% increase in speed.
. After that, I checked the hull and it has a pronounced hook in it. It seems the faster it runs, the more it wants to push the bow down I think.
. After that, I checked the hull and it has a pronounced hook in it. It seems the faster it runs, the more it wants to push the bow down I think.
09-27-2002, 07:08 AM
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Have Bob Teague or Reggie dial it in for you...
It will be AT LEAST 15mph faster.
On a serious note I would try going DOWN in pitch and/or try lab finished prop. Tinkerboater has a good point. What prop/rpm are you running now?
It will be AT LEAST 15mph faster. On a serious note I would try going DOWN in pitch and/or try lab finished prop. Tinkerboater has a good point. What prop/rpm are you running now?
09-27-2002, 07:57 AM
#8
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What are your dyno numbers and what else did you do to get an extra 100 HP? If you really gained that much there should be somewhere around a 5 MPH gain. On the flip side of what Tink and JDNCA have said, your new cam may allow you to turn a larger pitch prop nearly the same RPM as whatever you were running with the stock motor. Try a lot of props!!! Post your dyno numbers and I am sure some of the experts on the board can help you find your lost speed. Remember merc rates their motors at the prop, and a lot of shops report dyno figures at the crank with no accessories and tubular full runner headers. Hopefully this isn't the case, but 100 HP from a cam change seems like a bit much on a stock motor with no other mods. Good luck!!!
09-27-2002, 08:34 AM
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I agree with Wette Vette. 100hp from a cam change is a lot and may only show up on the dyno. If you are running stock Mercrusher exhaust - that is probably most of your limitation.
PaulO
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09-27-2002, 04:10 PM
#10
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Cuda, Pull your anchor up! Is that all? Is that 330hp a BB or the GM 330hp SB. If that's the GM SB that's labled "not for highway or marine use" , a friend of mine had a 260 and went to the 330 and got very little. He then changed the cam and got tear your ass out acceleration. This is what he was really after ,for water skiing
Is that all? Is that 330hp a BB or the GM 330hp SB. If that's the GM SB that's labled "not for highway or marine use" , a friend of mine had a 260 and went to the 330 and got very little. He then changed the cam and got tear your ass out acceleration. This is what he was really after ,for water skiing
Last edited by mopower; 09-29-2002 at 09:09 PM.
