'06 Mercury 115HP 4-Stroke Prop Questions

[TheChad]

Hey all,

I have an '06 Lowe Fish & Ski 175 (17.5'), It's a Deep-Vee Hull.

I also have an '06 Mercury 115HP 4-Storke Motor.

When I bought the boat the dealer had installed a 19-Pitch aluminum prop. I found out almost immediately that this was the wrong prop for the boat/motor, fully loaded boat (4-people & fishing gear) it would run 40 MPH @ 5200 RPM, and would not plane.

I then tried a Mercury Vengeance 18 Pitch Stainless Steel Prop, with a fully loaded boat (4-people & Fishing gear) it would run 38-40 MPH @ 5400 RPM.

I then tried a 17 Pitch aluminum, with a fully loaded boat (4-people & Fishing Gear) it would run 42MPH & 5500 RPM.

The 17 pitch prop was the only prop that will plane with 4-people behind the windshield. I also had the engine raised up 1 hole on the transom, which gave me a little better holeshot, and about 50RPM more. The Redline is 6000RPM, but it doesn't seam like I can get the engine to tach out to 6000RPM, and I am thinking if I go any lower in pitch I am going to start loosing top speed. The 18p prop was the fastest when runing light (2-people light gear), which was 48MPH @ 5500RPM

I am not untimatly concerned about top speed, but I don't want to drop my top speed too much under 40mph.

Currently I am running a 16 Pitch Mercury Vengeance Stainless Steel Prop, but I am actually considering going to a 4-blade prop. As my kids are getting older, I find us doing more and more tubing, which causes an entirely different problem.. With my current 16p Prop, the boat doesn't plane very easily when pulling a tube, and when I do a hard turn, the prop "slips" in the water which brings us down to a crawling speed before the prop gets "traction" again.

I was thinking of going to a 14P-15P 4-blade prop. The other thing is, that their are soo many different props, how on earth can one decide which would be best?

This boat is a Fish & Ski, it's primary function is family fishing, we often have a full boat 4-5 people, but it needs to be able to pull the tube better as well.

Thanks for the help,

-TheChad

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

I have a 03 115 4 stroke, same motor yours on a 18 ft bayliner fish n ski. I run a 16p vengeance also and it is perfect on my boat. It tachs out at 6000 on the money and runs about 41-42. I do have a 15 pitch for pulling heavy people out skiing. If I were you I would take a look at the new merc spitfire series, it's a aluminum 4 blade that have gotten great reviews. They come in 15 and 16 pitch. I really want to try one myself. One thing you def. want to do with that motor is run it as near 6000 rpms as you can, don't want to lug it.

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Yeah, I was actually thinking of either the Spitfire, or the Trophy Plus..

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

If u do try a spitfire please post your results, I really want to compare a 16p vengeance vs 16p spitfire. Trophy's are sweet but pricey

 

[steelespike]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

You can't expect it to run 6000 rpm with what amounts top a full load. Unless you prop it for the full load If you prop it for 6000 with a full load you will loose speed and gain hole shot.You need to prop it for 6000 with a light load Probably a 17" pitch.
I wouldn't expect it to plane very well with 4 people behind the wind shield. Thats about 600-800 lbs in the rear half of the boat add the motor, guessing, 300-400 lbs. you have about 1/2 a ton back there.Then figure in the 4 stroke struggles with hole shot.
You might look up the 115 tests on the merc motor site. I see a lot of 17"spitfire on boats with a dry weight of 1357 to 1550 lbs
rpm of 6250,to 6150 speeds 41 to 42 mph.A couple of Lunds a little over 1100 lbs each dry. a BM 14" and a BM 19"
6150 at 44 mph and 6000 43.4.
When testing props you need to stick with the same material.
When towing you need to balance the boat with some weight forward.
If your going to be towing with a crowd prop for about 6000 with the load.
Something like smart tabs added carefully with just enough tension to improve hole shot will get you up
and help stay on plane at reduced throttle. Also may help control no wake speed wander.
Don't know if the Vengeance prop is said to have bow lift; if it does its probably a poor choice for hole shot.
You say the boat runs 40 mph but does not plane. ?? Doesn't make sense.

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

@ Steelspike, the boat planes, when full it struggles to get on plane, and when towing a tube it REALLY struggles to get on plane.

When on plane at full throttle it'll go about 40mph +/-..

I guess my biggest issues are Holeshot, and when towing a tube, when I go into a tight turn the prop "slips". I do have a SE Sport High Performance Hydrofoil installed.

-TheChad

 

[steelespike]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

The Solas Amita and the Spitfire appear to have good results though I don't have any personal info on the Spitfire.
Both should resist ventilation. Do you trim down for turns?
As I recall you raised your motor a hole it may be too much for tight maneuvers.
When lightly loaded does your motor produce numbers similar to the 115 tests on the Merc site?
Boats of similar size and style running a 17 spitfire produce rpm 6000 or higher and speeds easily exceeding 40 mph.

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

I'm with steel spike, if your boat goes 40 plus it's strange that you struggle to plane out. Yours and my boat probably have similar weight, and mine does well pulling 2 tubes with 3 in the boat. I think a 15p 4 blade would be perfect. Just out of curiosity what is the max HP rating for your boat?

 

[Ccfbailey]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

I have a Lund rebel 16.5 with a 90 4 stroke. 17p spitfire. 6000rpm and 43 mph loaded. Quick to plane. Have not towed with it though. I read the 115 is good for 6500 rpm. Seems odd that you're way under 6000 with a 17p on a similar boat to mine.

 

[jestor68]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

RPM range is 5800-6400 for the current model 115. Your "06 may be 5K-6K. Either way, 6K is the rpm to shot for, for best over all performance.

The Vengeance is basically the same design as the Black Max; only SS material. Nothing special about it.

If the prop is blowing out easily in turns, you may have raised the motor too high for that particular hull design.

A 4 blade should help with hole shot and holding in turns. Propping it to get the rpm to 6K with the 4 blade should call for a reduction in pitch if you're only getting 5500 with the 3 blade, seeing as how you reduce an inch of pitch to MAINTAIN rpm when switching from 3 to 4 blades.

 

[steelespike]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

We need to keep in mind the rpm he is quoting in his opening post are fully loaded 4 people and gear.
I don't think we have any specs with him alone.

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Chad any updates on your prop search

 

[BobGinCO]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

'06 Mercury 115HP 4-Storke Motor

This boat is a Fish & Ski, it's primary function is family fishing, we often have a full boat 4-5 people, but it needs to be able to pull the tube better as well.

Those Storkes must beat their wings awful hard!!!

I just can't imagine what kind of fishing you're doing at 40 MPH!

Your WOT RPM's should be between 5000 and 6000, so ALL the prop choices you used are OK. I'm running a 13 on my engine, because of the elevations I run at, and my boat weighs 3000 pounds...

If you're hitting 6000 RPM's, you're right on the edge of being under-propped. I would try to keep it at or below 5800 at WOT.

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Just picked up a 15p spitfire today. Won't be able to run it till Monday but ill let you know how it does.

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Just picked up a 15p spitfire today. Won't be able to run it till Monday but ill let you know how it does.

Please do! I cannot find a local dealer that has a spitfire prop in stock.. I don't know if I'll want to get a 15p or a 16p.

I originally wanted just enough holeshot and speed.. Even though its a fish & ski, it was mostly fish.. Now that my kids are getting older, and I realized all the local lakes arnt as big as I thought they were, I'm not nearly as concerned about speed.. Though I don't want to go excessively slow, I definitely want more/better holeshot and better "hold" in tight corners..

I may have to lower the engine back down 1 hole.. Originally I raised it one hole to gain RPM as the dealer I bought it from propped it with a 19p prop which had the motor running like a slug and no where near the RPM it was suppose to run at..

I think I am going to go with a 15p spitfire and if the RPM's are too high, I can lower the motor back down 1 hole..

Thanks everyone for your input..

-TheChad

 

[pokman]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Chad, started a thread about the spitfire. Think it would work great for you. FYI they don't make a 16 pitch, I thought they did, only 15,17,19

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Okay, I just ordered the Quick Silver Nemesis from the dealer. was $145. The Mercury Spitfire was $205.

I don't need the hub and everyone says the Nemesis is the same prop, so I figured I'd save some $$.

I will definitely post my review once I get it. I did order the 15p. I think it will be the perfect ticket.

Thanks everyone.

-TheChad

 

[blackhawk180]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Wish I'd caught this thread earlier but had to work today. I run a similar boat (Alumaweld Blackhawk) with a pretty deep V and the same motor with the same problems. I ended up with a Solas 13x4 and love it. I run pretty heavy with a kicker, Scotty electrics and a ton of fishing gear + at least one more big guy. I tried a 14x3 aluminum but found the 4 stainless to be far superior in fuel economy, hole shot and cornering. I'll be interested to see your results.

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Okay,

I picked up the prop yesterday, Installed it today! 5 minute's, Done!

I will take it for a lake test Monday and post results.

One thing I noticed right away, is that the 16p Vengence Stainless Steel prop weighs about 2x what the new 15p Nemesis weighs, So that might help for getting the RPM's up.

Thanks,

-TheChad

 

[TheChad]

Re: '06 Mercury 115HP 4-Stroke Prop Questions

Okay, I took the boat out today.

With just my wife and I in the boat, of course it jumps right on plane, but WOT I am @ ~6300 RPM, and 38-41 MPH (GPS).

The water was very choppy so I couldn't do much testing in hard cornering, but a cut as much of a U-turn as I could and it seemed to hold better.

It's not really a true test, but a good first run. I will be going on a 7-day camping trip in about a week and will the boat will go threw a full test run.

I will post back!

Thanks,

-TheChad