Need help with a new prop size. Heres a run down, 1989 larson senza 210LX with a alpha 1.5 drive. Chevy 350 , heads , intake and comp 268 cam motor. Engine runs around 4200-4400 rpm and 54-55 mph on gps. The prop is a ss mich raptor 14.25x21 .

Iam looking for more top speed and think maybe a 19 might help me get over the edge and more in the power band. What band and size do you guys think. And should i stay with a 14.25 or go smaller

thanks guys for any help

its a 21ft boat , forgot that

Welcome to OSO

What kind of power are you making? I would try a Merc LaserII or Enertia. The LaserII is 13.7/8" in dia. with lots of cup for carrying the bow and pretty thin blades, so you should try both the 19" and 21". As far as the Enertia goes, it's the same dia. as what you have now, but it comes in a 20" and that could be the ticket. My best bet would be one of the LaserII's. You could also try and contact someone like DAH Propellers or Bblades and see what they can do with what you have now.

heres a fast run down

stock 4 bolt main truck block

Pro Action Redtopline Heads 180cc x 64cc
Comp Cam Beehive Springs Good For 550 Lift
Ferrea Valves 1.94 Intake / 1.50 Exhaust

billet msd dist and box

Weiand Stealth Intake Manifold & 750 carb
XM262H cam
262 adv dur
258 adv dur
218 @ .050
224@ .050
.462 in lift
.477 ex lift
112 center

power band 1300-5600

dry weight is 2650lbs so its well over 3000 i'am sure. And with revs to 4200-4300 in the powerband it cant make to much power that low i would think. maybe 240-250hp at 4200rpm if that

Not real sure how props act, I know a lower prop is better for tubing and stuff but will it slow me up or will it get me in the higher rpm were this engine makes more power and go faster then it does now.

Well in your case, where exact power is not known, testing is key. Yes normally lower pitch will yeld better pulling power out of the hole, but if you are running too much pitch, you could also rob speed, since you are not useing the engine to its full potiental. The smaller dia. laser with the thin blades should spin faster than your 14.25" prop, and therefore yeld more speed and rpm, hence the suggestion to still try a 21". But how a certain prop will behave in a certain setup, may vary, and therefore testing is needed.

If your local prop shop has a good selection of props, this is what I would test, and in that order.

LaserII 19" and 21"
Mirage+ 19"
Enertia 19" and 20" (A bit of a long shot, but worth testing)
VenSura 19"

Thanks for the help , i'll see what i can do with these props you listed. I cant find a prop guy around here in maryland or anyone that runs any 19 pitch. My buddy does have a 21 mirage + thats been labbed i think he said and a 23 clever he said i can try but thats it

You are welcome. The 21" labbed prop sounds like a cool prop to try. I doubt the 23" cleaver will work at all. Bblades has a test program.

Keep us posted

not sure on the speed but the cleaver 23 killed the boat, about 3800 rpm, i put the raptor back on and got 4300

still no luck with finding a 19 prop. but i think thats going to put me in the 4700 range or better i hope, now if it picks up speed thats another thing

well guys the i took it out today with a gps, me the wife and two kids with a heavy cooler did 55mph at best. Me and the cooler did 57mph at best. Thats with the 21x14.25 raptor at around 4300-4400 rpm .