Another Prop Question (Pitch Up or Down?)

[RangerGuy]

Ok,

 

So I'm going to put a Mercury Vengance on my 75HP Yamaha

4 stroke after reading several reviews on this prop. I'm looking for more bow lift, and no bow bouncing

 

Right now its got a Yamaha Aluminum K series 13 1/4 x 17p

on her. She's getting 6000rpm and tops out at 38.5mph.

 

Speed drops to 36-37mph at 6000rpm with a full load (3 adults, 2 dogs and fishing or hunting gear.

 

Should I go 16,17 or 18p?

 

If anybody is running with this prop on a 75 yammie I'd love to hear your thoughts.

 

Thanks

 

 

[ecmilley]

whatis max rpm for the engine? i would guess its is 6000 don't go down in pitch that will increase rpm i would stay the same unless you can test both pitches out, going to a 18 will give you more top end but will sacrifice hole shot and easy planing

[Terry]

The same or next size bigger. It wouldn't hurt to have your rpm a little lower

 

[RangerGuy]

Thanks everyone :-)

 

Max rpm is 6000 rev limiter is supposed to kick in at 6150

I believe.

 

I will try the 17p first. I'd love to keep

my hole shot and plaining characteristics, see plains under 3secs with a full load.

 

To be truthful I haven't even gunned it straight to full

throttle yet as it pulls me back so much.. I'm not sure what will happen hehe!

 

I will post results next spring :-)

[RangerGuy]

Thought I'd provide an update...

I tried a 4 Blade 15p stainless, it gave great hole shot and smooth trolling , good bow lift but speed was very low 33mphlots of prop slap and fuel mileage was 25% worse, rpms pretty high 6100.

 

kawartha Prop Repair was awesome they allowed me to exchange the prop I got off them for a Vengance 18p...What a prop...though I think a 17p Vengance would be perfect the 18 is good.

 

Alone I get 37 mph @5500 with 3 adults I get 36 mph @ 5200 -5400 depending on trim level with plenty of lift and no prop slap.

 

So pretty much the same speed but less rpms and better ride, fuel mileage is still up in the air. But considering how much I was testing holeshot etc. and the very little movement in my gas gauge moved This weekend would say its good lol!

Edited July 31, 2013 by RangerGuy

[squiggy]

for every drop in pitch will equal approximatly 200 rpms increase and vice versa. the 17p will bring your rpms up to about 5700 according to the numbers you have when alone in he boat. im going through the same thing trying to get mine setup......almost there (crossing my fingers) . my boat wont turn a 19p tempest plus but the 17p is almost bang on. gotta sell the 19p now....it gets expensive testing props. also if your trying out 4 blade props.....a 16p 4 blade should turn the same rpms as a 17p 3 blade

[RangerGuy]

Yeh ...testing can be very expensive.. Luckily. This one only cost me the difference in price because I returned the previous 4 blade SS I bought from Kawartha Prop repair, what a great place

 

I'd really like to test the Vengance 17p... Like you said I'd be up a little higher to the engines top rpm again and maybe get a mile or so faster..but not a big deal... I never expected this boat to be a speed daemon hehe!

 

Really, If I don't find one to test I'm ok ..this prop is much better than the 4 blade as far as prop slap and clucking goes... I only get prop rattle and the lowest rpm setting with my yamaha troll control buttons (500 rpm).

 

I think a Flow Torque up will get rid of that.