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need prop help

897 Views 13 Replies 4 Participants Last post by  gigedygigedygo, 
G
i just finished my winter project on my 4.3, 4bbl carb and intake,cam,bigger valves/springs, comp cam,stainless risers and theu hull exhaust, my problem is in the prop selection, i had a aluminum 3 blade 19pitch last season and the new motor is too strong for it, tried a high five 23pitch and no it's 10 times worse, crazy slip no hole shot and still have 1/4 throttle before wot, and engine hits rev limiter. the drive is an alpha with 1.81 gears. where should i start for prop? bigger than 23p or drop ratio in drive to keep pitch lower? 3 blade with bigger diameter? or 4? i think that the high five is no good for this boat. any hely would be appreciated here guys
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W
how big is the boat... length approximate weight?

most importantly, do you have accurate speeds for your rig with the older prop? including accurate wot by gps and rpms on a good tach?

What was your engine configuration before doing the minor modifications this time around? Are you still iusing the factory manifolds? or did you upgrade those when you changed the risers? I'm assuming edelbrock manifold and carb or something very similar... What rpm is the rev limiter at and which heads do you have on it now?

Not being familiar with your boat, I would recommend trying a laser 2 in 23 or maybe 25... and go from there... can make up the hole shot with venting if the 25 is a little much.
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G
boat is 19.5 ft 2300lbs
don't have acurate gps# but does not handle or go as fast like last year and alll i have is more power,i was thinking at least a 25-26 pitch 3 blade tried a 23 pitch high five......junk worse than ever, yes it is edelbrock 4bbl intake and 650 cfm carb jetted down for 4.3
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G
oh yea before mods was bone stock thru prop exhaust and all, basic 2bbl 190hp merc
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W
the only thing with the exhaust that will make a difference at all is the manifolds

have you adjusted the jetting and metering rods from the calibration kit from edelbrock? they're probably a little lean for your set-up. check the plugs at east.

there's a good bit of difference between

laser 2 and hihg 5 are a world apart.

I'm hoping you meant edelborck 600 cfm.. marine carb...
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M
I run a Laser II 21P on mine and it made a huge differance over the no name SS 19P. I would see if you could get your hands on a Laser II 23P and try that.
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G
im gonna try a 21x14 1/2 vengance this weekend to see if there are improvments, then i will know that 3 blades is the way to go and start going up in pitch from there, yes the manifolds have been changed to glm aluminum and hardin ss risers

and yes as well 600 marine carb has been adjusted with the edelbrock kit for a marine 4.3
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W
the laser 2 would probably give you a good bit mroe than a vengence on your boat... more rake and thinner blades, etc...

Also, if you haven't looked carefully at your plugs after a high speed run, you migh be leaving some power (and longevity) on the table. My last healthy vortec v-6 required a few stages richer jetting than supplied in the edelbrock 4.3 calibration kit... you may have a significant amount more horsewpower to unlock making pop selection a moot point at this juncture... I'm not trying to talk down to you, it just sounds like your set-up bears some similarity to my previous one... my vortec v-6 would push my 18 ft checkmate up to 60 mph with a 26 pitch turbo, but that prop ventilated in the corners. a laser 2 in 23 pitch was by far the best all around and ran me mid to upper 50's consistently... Our weights are probably similar... and horsepower probably was in the same range or near as well, gear ratios the same... I was also probably running the same carb and intake, etc...
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G
wtfo- you are in no means talking down to me at all i appreciate the words of wisdom, im going to the lake today and will check a plug after a run and see what they say,i can't believe 60 mph that's awesome
the 21 vengance prop worked really well and gave me more top end, so just to get on the water i picked up a cheap 21p 3 blade made by patriot??, so the concensus is to try a laser prop?? venting is kinda moot now as it goes through the side of the boat
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W
laser is a great prop on a smaller boat...

I'm also liking my solas 4 blade el cheapo a lot now that I've got more power... before dropping gear ratio, was running a hydromotive 29" that was awesome... now the 21 or 23 seems to be the stuff... have been on the water every day for the past week... life is good!
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G
wtfo what size jets did you increase to and was it primaries and secondaries or just one, did you change the metering rods and springs also what elevation are you running at just wondering to see if i can get in the ball park
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T
gigedygigedygo said:
i just finished my winter project on my 4.3, 4bbl carb and intake,cam,bigger valves/springs, comp cam,stainless risers and theu hull exhaust, my problem is in the prop selection, i had a aluminum 3 blade 19pitch last season and the new motor is too strong for it, tried a high five 23pitch and no it's 10 times worse, crazy slip no hole shot and still have 1/4 throttle before wot, and engine hits rev limiter. the drive is an alpha with 1.81 gears. where should i start for prop? bigger than 23p or drop ratio in drive to keep pitch lower? 3 blade with bigger diameter? or 4? i think that the high five is no good for this boat. any hely would be appreciated here guys
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Something is crazy off here. At best your turning 240 hp and with a high five you effectivly went up 5 inches in prop..aka 60hp and 5" in prop and a rev limiter... :dead:

That is a efi function...carb's need to electronics...No flame it the post seems to be missing a few thing's
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G
the new thunderbolt ignitions use a ignition module for the spark advance as there is no weights or springs in the distributor and built in there is a rev limiter that is set at about 5200 rpm, i think that the high five didn't work cause of the really small blade area, i don't know what else to tel you i have a 21p 3 blade stainless on there now and it works real good but after reading what wtfo wrote i think i can find more power in there just have to figure out where to go with jets or metering rods etc
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G
the new thunderbolt ignitions use a ignition module for the spark advance as there is no weights or springs in the distributor and built in there is a rev limiter that is set at about 5200 rpm, i think that the high five didn't work cause of the really small blade area, i don't know what else to tel you i have a 21p 3 blade stainless on there now and it works real good but after reading what wtfo wrote i think i can find more power in there just have to figure out where to go with jets or metering rods etc
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