Good Prop for a Merc 470 3.7L?

[82shark]

Newbie, question here, hoping someone can help. I have an older 1988 Wellcraft Classic 190. The motor is the 3.7L Merc 470 with an Alpha 1 outdrive. The prop that was on the boat when I bought it got bent at the boat ramp one day (long story). Anyway need to replace, and the guy at the store seems to think a 14.5" x 17"P would be good fit for that motor and boat. The old prop was a Quicksilver SS (forgot model number) but was a 13.75" x 21P. The boat did have some trouble pulling up a slalom skier, but did fine for two skiis and tubes. Would a 17"P be that much loss of top end and would it help the low end holeshot? or should I go with a 19"P?

Thanks for your help.
Ed

 

[rallyart]

Re: Good Prop for a Merc 470 3.7L?

I put a Mercury Vensura 4 blade SS on mine after trying a few on my 18' 1980 I/O. I drilled the vent plugs to 1/4" which helped the starts. Mine is a 21" pitch and the motor will just redline if the boat is unloaded and trimmed correctly. (41 mph) My top speed was the same as with my 21" pitch 3 blade SS prop but the holeshot is better now. With a 17" pitch on mine I could seriously over rev the engine, on my boat.
If you know your max. RPM with your old prop you will make a better decision. I think a 17" pitch would be too big a change but it will definitely help the holeshot. If you just change to the 19" you are still picking up a 10% increase in pulling torque.

Some stores will let you exchange a new prop a few times until you get the right one for your boat.

 

[82shark]

Re: Good Prop for a Merc 470 3.7L?

Thanks for the reply. I've run mine at around 4000 RPM comfortably, but have gunned it up to 4300 to 4500 a few times for short bursts. It boggs sometimes with the existing 21" prop, so maybe the 19" is going to be a tad better. Top speed isn't what I want, just a decent cruise speed and pulling power for the kids toys.
Ed

 

[SparkieBoat]

Re: Good Prop for a Merc 470 3.7L?

you may consider a vented 21 pitch...sounds like you are already in the correct RPM range with the 21..a vented prop will give you more hole shot and keep your top end.