need prop help on 115 merc

[raftdaddy]

i just bought a new 2010 17.5 princecraft fishing boat with a 115 merc 4 stroke. i'm pretty sure the aluminium prop is correct it is a 13.25x17p (77344a45p17). i do max at 6200 rpm and my gps is 39mph. my problem is that is sucks out of the hole and the break in recommends not cruising above 4500 rpm and the boat barley stays on plane.i am thinking of changing to a 19p ss possibly a laser 11 or vengance. will this give me more performance? and how much top end will i loose? i think 39mph is a little on the low side allready.

 

[reddogg]

Re: need prop help on 115 merc

A general rule is a change in pitch up or down is worth about 200rpm. It's almost impossible to tell you exactly how much speed you'll gain or loose, but in general a higher pitch prop will give you better hole shot. A 4 blade prop is also good for hole shot though not so great for top speed. Pitch is measured in inches so your 17 pitch prop will move your boat 17" in one revolution of the prop. Your best bet is to find a place that will let youn try out a few props till you find one that works for you. hope this helps.

red

 

[QC]

Re: need prop help on 115 merc

A general rule is a change in pitch up or down is worth about 200rpm.

Generally a 1" change will do this.

in general a higher pitch prop will give you better hole shot.

Backwards. Lower pitch = better hole shot

Pitch is measured in inches so your 17 pitch prop will move your boat 17" in one revolution of the prop

Theoretically. The difference between theoretical and actual is called slip and it is very important, yet difficult to understand etc.

 

[3dees]

Re: need prop help on 115 merc

I would try a ss 19"p 4 blade. better hole shot and better stern lift. less boat in the water usually means more speed. I am running a Solex Rubex 19p on my 19' alum. bassboat with a 115 optimax. you may lose 150-200 rpms but you will still be in the range. either that or go with a 17p 4 blade.

 

[Bamaman1]

Re: need prop help on 115 merc

Take your boat back to the original dealer, and tell him that you're not satisfied with the performance. He owes you a propeller (of the same cost) that properly propels your boat--within factory RPM specs.

Any quality marine dealer should comply. I've even gone to the lake upon dellivery with a dealer that brought 4-5 propellers to make sure they got it right.

 

[sschefer]

Re: need prop help on 115 merc

You can improve the hole shot on that 115 with a 4 blade. Generally a drop in pitch of 1" and diameter of 1" will do the trick. I'd go with the 13-1/4 x 16 Stilleto Bay Pro I. Your top end is about right for that boat and motor combination. You have to remember you're a deep V and sacraficing top end for ride. My 18' Starcraft topped out at around 35 with a 115 and the Bay Pro I prop. It was quick to come up on plane.

 

[raftdaddy]

Re: need prop help on 115 merc

thank you all for your response. my dealer had said he would let me try a 17p with a diffrent "cup"on the blade for more bow lift.he said mercury has matched my prop and motor with my boat and not to stray from that.so i guess it's trial and error time. but if i go my own way i have a good starting point from you all. thanks again