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Old 25-01-2014, 09:26 PM   #1
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Join Date: Jun 2010
Posts: 16
mini zap cat questions

as above just looking for advice on the best position of the center of the prop in relation to the hull

3m thundercat
yamaha 20hp 2 cylinder 2 stroke
powertech sra 12p
32knots top speed 1 up

ive been running center of prop level with the bottom of hijackers,

read a few posts on the 4.2m thundercats saying the ideal position for the prop is to have it central with the center of the hijackers (50mm higher than my current setup) providing it sucks water,

just wondering if any one can confirm this, ive added another bit of 50x50 box on top of my transom so that i can raise the motor, its currently bolted on later to be welded providing it all works out okay,

ive also added 2 lower holes so i can drop to -15mm from center and -30 from center taking me 20mm away from the old position with the saddle now sat on the box

also looking at a ron hill cleaver as i can seem to find anything else thats 10 spline and 10" diameter

ive recently had the ports polished ive fitted the 25hp exhaust and carbs as thats the only differance between the 20 and 25hp had the timing advanced 2 deg @ wot

id like to up the compression as its only running 95psi, but my squish is .50mm can i get it skimmed and the squish re machined, and how much should i get i skimmed by id like to still run on the higher octane pump fuel
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