4 or 5 blade prop conversion

[fossill]

Currently running a 14x23 3 blade prop on a 4.3 190hp merc. Engine runs at 4600 rpm WOT and 48mph. Boat is a 2008 18ft model. Recomended RPM is 4400 to 4800rpm WOT. With 5 people onboard the boat will come on plane in about 3 seconds. Not exactly sure how long to plane with a skier or tubers behind.
Anyways, I'd like to convert to a 4 blade prop or maybe a high-5 for better performance pulling skiers and tubes while still being able to do 40-45 mph.
My question is, do i stay with the same prop pitch/size when i convert or do I change down in size? Any suggestions from experienced boaters who have gone to a 4 or 5 blade prop from a 3. Or is it just as well that I stay with the 3 blade model.
Thanks in advance for your advice.

 

[ramster]

Re: 4 or 5 blade prop conversion

If your running 4600 with a full load I would try a 4 blade stainless 14X22, I like the Mich. Wheel Apollo because I worked great for me, should put you at 4800RPM without losing much, if any topend. The Stilletto BayPro II I heard is a great prop too, but it probably has more agressive cupping and will put at slightly less rpm. Cheap aluminum props like the Vortex or Mercury will work ok and give decent holeshot but likely over rev in a 14X22. just my two cents.

 

[sleeper]

Re: 4 or 5 blade prop conversion

if that 14x23 stock prop is a black max, going to a 14x22 4-blade stainless steel will kill your rpm. I would look at a 14x20 in a 4-blade stainless. Between the material change, cupping, and a 4th blade, you need to drop more than one pitch to account for it all.

I have a similar combo. 4.3 TKS 190hp, alpha 1 and a heavier 19 ft boat. I had a 23 pitch stock and it ran 46-4700rpm at wot. I changed to a 14x21 turning point hustler aluminum prop and it ran 4800rpm (prop cupping kept rpm from raising more). Then I went to a 14x20 stiletto bay-pro II stainless 4-blade, and my WOT rpm went to 4600rpm. I decided then to get a watersports prop for heavy loads and bought a 14x18 stiletto bay-pro II stainless 4-blade. It over-revs the engine when lightly loaded (49-5000rpm), but when I have a large load of people and do watersports it is great. I have the 14x20 4-blade bay-pro II on ebay right now because the 18 pitch is perfect for watersports, and the 21 pitch TP is great for cruising.

 

[fossill]

Re: 4 or 5 blade prop conversion

OK, thanks for the helpfull advice and info. What are thoughts on a 4 blade aluminum prop. Reason I ask is that I'm still fairly new to boating and am a bit leary on hitting a prop lake bottom in shallow water. The aluminum would have less potential to do stern drive damage. Thanks again.

 

[junior1113]

Re: 4 or 5 blade prop conversion

21 pitch 4 blade alluminum will do what you want. might bring rpms up 100 or so but hole shot will be better. and youl have slower on plane speeds. i love 4 blades. hold the water better