Opinions on my planned propeller change

[JTwelve]

I have a 4.3L Mercruiser with a 1.62 ratio Bayliner Cuddy Cabin. Current prop is a 3 blade, 19 pitch and WOT Is 4400 RPMS and top speed is 43 mph.

Mostly use it for water sports, ski, wakeboard, tube. And I usually have 5-6 adults on board. Time to plane with a full group of adults can be incredibly slow. I dinged the prop today at the lake, so I’m definitely buying a new one.

Better hole shot would be nice, but current performance isn’t terrible. What is killing me is an agonizingly slow time to plane with a full boat of adults.

All that being said, I’m planning to buy a 4 blade, 14 diameter 19 pitch prop. What would I lose with a 17 pitch? What would I gain? Current plan the better decision than the 17?

 

[tpenfield]

Current prop is a 3 blade, 19 pitch and WOT Is 4400 RPMS and top speed is 43 mph.

. . . .

All that being said, I’m planning to buy a 4 blade, 14 diameter 19 pitch prop. What would I lose with a 17 pitch? What would I gain? Current plan the better decision than the 17?

No . . .

4.3L engine and a boat load of people is not a good mix, but staying at the same pitch and adding a blade is going to be worse. I would certainly go to a 17" pitch prop. Can't really speak about the diameter, because you did not mention the diameter of the current prop.

Are you aluminum or stainless steel for the prop?

 

[dingbat]

Complaining about hole shot then going to a 4 blade of the same pitch doesn’t make sense. If anything, you would need to drop down in pitch going to a 4 blade
M
What is your normal WOT? What is your loaded WOT?

 

[harringtondav]

Pitching down to 17 will improve your hole shot. It will also raise your WOT rpm to approx. 4600 which is OK for the 4.3. But it will also lower your WOT speed, which shouldn't be a concern if you're looking for better hole shot and lower speed water sports performance. Per above, a four blade could improve cruising efficiency but not hole shot.

 

[Scott Danforth]

if you add blades you must drop in pitch

I would drop down to a 3-blade 17P if you plan on having a boat load of people in the boat.

 

[JTwelve]

Complaining about hole shot then going to a 4 blade of the same pitch doesn’t make sense. If anything, you would need to drop down in pitch going to a 4 blade
M
What is your normal WOT? What is your loaded WOT?

That’s why I’m asking. I’m still learning. As I understood it, all characteristics the same, 4 blades would be better out of the hole than 3 blades. Is that not accurate?

Based on this discussion, I also bought a 3 blade, 17 pitch prop. Both are aluminum. I figure I’ll buy aluminum until I know exactly what I need, then I’ll go with stainless.

 

[JTwelve]

No . . .

4.3L engine and a boat load of people is not a good mix, but staying at the same pitch and adding a blade is going to be worse. I would certainly go to a 17" pitch prop. Can't really speak about the diameter, because you did not mention the diameter of the current prop.

Are you aluminum or stainless steel for the prop?

Current prop has a diameter of 14.5, 3 blades, 19 pitch.

I ordered 2 props:

4 blade, 14 diameter, 19 pitch and
3 blade, 15 diameter, 17 pitch

For my stated performance goals, everyone seems to be saying the 3 blade is the better choice. Is that right?

The drop in diameter of the 4 blade over the current prop still won’t be enough to overcome the addition of another blade?

 

[89retta]

I see a lot of people saying you lose speed with a 4 blade. My boat actually picked up speed. Used to have a 3 blade 19 4.3 Volvo GXI would run about 45mph on gps and would hit the rev limiter sometimes. Switched to a 4 blade 19 runs 48 mph sometimes 50 and 4800 rpms. Comes out of the hole good. My thoughts are the 4 blade helps lift the stern more thus allowing for a few more mph

 

[JTwelve]

I see a lot of people saying you lose speed with a 4 blade. My boat actually picked up speed. Used to have a 3 blade 19 4.3 Volvo GXI would run about 45mph on gps and would hit the rev limiter sometimes. Switched to a 4 blade 19 runs 48 mph sometimes 50 and 4800 rpms. Comes out of the hole good. My thoughts are the 4 blade helps lift the stern more thus allowing for a few more mph

Good info. As I research this in a few different places I’m getting a little bit of mixed information when it comes to
subtle differences between minor changes in these three variables: diameter, pitch and blade number.

Its difficult. I cancelled my 4 blade, 19 pitch order and now have a 4 blade 17 pitch coming. I’m wondering if that wasn’t a mistake though.

 

[tpenfield]

You never know until you try it. What diameter is the 17P 4-blade that is now on order?

In 4 blade props, I'd be trying a 14" 19P or a 14.5" 17P

 

[89retta]

The 4 blade 17 you have coming is also a good prop when you have a heavier load or doing water sports. I also have one of those for that reason.