80 mph 24'
#131
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Joined: Jul 2010
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From: Deerfield BCH, FL
awe too late i won a bid on ebay for a 23plus mirage..
Ill try it i can always put back on ebay after testing it, i figured it would have more pitch, maybe i should get a 25...?
Cdail. a python is a lighter boat if im not mistaking, and like you said 450hp, i was told around 500 hp from bob.
I just figure i can push more prop since im still at 5000 rpm
Ill try it i can always put back on ebay after testing it, i figured it would have more pitch, maybe i should get a 25...?
Cdail. a python is a lighter boat if im not mistaking, and like you said 450hp, i was told around 500 hp from bob.
I just figure i can push more prop since im still at 5000 rpm
#134
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Joined: Aug 2010
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From: MA
Why u fig loss of 3 with tabs? Running em tucked up? Just due to extra wetted surface area-drag?
#135
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Joined: Jul 2010
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From: Windsor, NC
Bob told me mine should be around 500 also. I wasn't real impressed with the dyno shop and how they dynoed the motor and I don't think the numbers are 100% accurate as far as the hp and torque goes. That motor had stock oval port heads and my new motor will have Merlin 320 cc Rect. port heads so I am hoping for 500-550but I am not going to dyno this one.
#136
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From: Deerfield BCH, FL
Where did you set his cam at? 0? I have the larger oval head 781 did you have peanut heads?
Guess no one has opinion on prop size....
Ya 450 sounds more like it, to be honest i changed heads, bob m cam, air gap intake, original 750 carb, the motor felt stronger but top end didnt go a mph faster then old ported peanut heads and old unknown cam maybe it wasnt stock... did 58mph with older prop, now with the larger prop hitting 63.5 with rebuilt motor and the new distributer with more timing but motor is pulling 200 more rpm then stock motor with smaller 21 prop, so the advance could have given more power.
plus new motor has domed ****ing pistons to increase compression, bob m cam didnt do much but cause reversion and a head ache
Guess no one has opinion on prop size....
Ya 450 sounds more like it, to be honest i changed heads, bob m cam, air gap intake, original 750 carb, the motor felt stronger but top end didnt go a mph faster then old ported peanut heads and old unknown cam maybe it wasnt stock... did 58mph with older prop, now with the larger prop hitting 63.5 with rebuilt motor and the new distributer with more timing but motor is pulling 200 more rpm then stock motor with smaller 21 prop, so the advance could have given more power.
plus new motor has domed ****ing pistons to increase compression, bob m cam didnt do much but cause reversion and a head ache
#138
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Joined: Jul 2010
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From: Windsor, NC
I can't really say whether Bobs cam made more power because the original motor was a big solid cam that wiped 9 lobes off the cam when the motor supposedly had 10 hrs on it. I just built a new motor and got the cam from Bob. I did make the mistake of installing the cam 4 degrees advanced because the cam card had 4 degrees advanced on it. I later found out from talking to Bob that his cams are made to be put in at 0 and the 4 degrees is built in. It shouldn't have really affected the total horsepower it just changed my rpm range. I had the large oval port heads that had been ported prior to me getting the motor. I don't know how good the port job was to help flow but they were gasket matched.
#139
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From: Deerfield BCH, FL
What rpm range are you getting at wot?
Did you go to a hydraulic roller or still solid...?
So your expecting 100 more hp out of merlin rec heads over old oval port heads?
Thought they flowed about the same as 781's
Did you go to a hydraulic roller or still solid...?
So your expecting 100 more hp out of merlin rec heads over old oval port heads?
Thought they flowed about the same as 781's
#140
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Joined: Jul 2010
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From: Windsor, NC
I went with a hydraulic roller and the max should be 5500. I bought some 320cc Merlin heads that should flow better than the 781's but I will lose a little torque down low but should make up for it and the fact my boat is pretty light it shouldn't effect to much. I didn't have the 781 heads but Bob said the heads I had were pretty close and still good heads.


