TUNING PROP EXHAUST HOLES

[CLAYC]

I recently purchased a'98, 18 ft Challenger Bass Boat outfitted with a Merc 115 spinning a 3 blade 22P SS Prop. At WOT it's turning 5200 rpm at 45 mph (boat speedo, not GPS). The hole-shot is seriouly lacking. I was told the exhaust holes in the prop can be altered to allow the prop to spin faster before it "bites" causing a better hole-shot. If you have any info on this it will be greatly appreciated.

 

[quantumleap]

Re: TUNING PROP EXHAUST HOLES

If you increase the hole size slightly, it will increase the lowend RPM's before it grabs the water. I have a 97 Mariner 125 on a 19ft fish & ski and turn 5300 RPM's at 47 MPH WOT with a 19p Ballistic SS. Your RPM's are right where you want them (5250 max on your motor) and your top speed is about right for your combo. You could probably go down in prop pitch with a conventional SS prop and recover your holeshot. Mine gets out of the hole and on plane instantly. Do a search on this site for props or prop holes and you can get a little more info. The search icon is highlighted in red above. Good luck and let us know if you find some improvement.

 

[CLAYC]

Re: TUNING PROP EXHAUST HOLES

Thanks for the advice. Located several sites with helpful info. I'm going to take the boat to the lake with a cordless drill and a set of bits to conduct some test & tuning on the prop.

 

[LubeDude]

Re: TUNING PROP EXHAUST HOLES

I do not know if this will help at all, but I just got a High five prop for my Merc 150 from Ebay, I was surprised at the size of the vent holes in it and they are factory cast holes as they have a little recesed ridge around them, they are about 3/4 ". I have never seen holes that big. It performs great, so if you just drill them out slowly you should be ok. Make sure you have really good drill bits, as stainless can be really hard to drill.