Propman - hook a brother up with a recommendation
 

Hi guys,

Need to get a little help with prop selection here.

Currently running a 2005 Merc 115hp 4-stroke.

Manual states min WOT: 5,000rpm
manual states max WOT: 6,000rpm

Current prop setup:
13-1/4" x 17p

At max RPM I am running at 5,000rpm and 35mph (on GPS). The motor is mounted to a 2005 Lowe FM175 (17.5' deep v-aluminum). That is with two adults, no fishing gear, and 15 gallons of fuel. Motor is trimmed properly, not certain what hole the motor is mounted in.

Any recommendations either for pitch or OD? Would like to operate a bit closer to the 6,000rpm range when throttle is wide open.

Thanks,
Rook

[QUOTE=rook-eye slayer;1408616]Hi guys,

Need to get a little help with prop selection here.

Currently running a 2005 Merc 115hp 4-stroke.

Manual states min WOT: 5,000rpm
manual states max WOT: 6,000rpm

Current prop setup:
13-1/4" x 17p

At max RPM I am running at 5,000rpm and 35mph (on GPS). The motor is mounted to a 2005 Lowe FM175 (17.5' deep v-aluminum). That is with two adults, no fishing gear, and 15 gallons of fuel. Motor is trimmed properly, not certain what hole the motor is mounted in.

Any recommendations either for pitch or OD? Would like to operate a bit closer to the 6,000rpm range when throttle is wide open.

Thanks,
Rook[/QUOTE]

When you get a chance check motor height. You want your cavitation plate even to acouple inches above the bottom of boat. If you can raise it it usually will give you more rpms and better performance. You may also want to try a 15 pitch also. to gain some more rpms.

For Comparison
 

Same motor on a 1700 (17.5 ft) Lund Fisherman. Three guys, fishing gear and 27 gallons of fuel - with a 17 degree prop, boat trimmed up, 5800 rpm puts me in the area of 40-42 mph GPS.

Rook,
What is the altitude of the waters where you run your rig?

REW

couple pictures, and a few more questions, and maybe a response
 

Hi guys,

thanks for the help, it's truly appreciated.

OK - here goes.

REW - I'm at whatever sealevel Minneapolis, MN is at (or within 100ft)

I've included a couple pictures so you can see what I'm dealing with as far as bottom of boat to anti-cavitation plate differences.

I am also looking at the water level line and thinking the motor is too low. When I put the throttle down, the back end of the boat acts like it is getting "sucked" into the lake and it takes a bit for the boat to get on plane.

I bought a 15p prop and am going to try that this weekend, but am looking for recommendation on the motor height.

In the pictures, the boat is level bow to stern, and the motor is level front to back. Measurements are from the garage floor.

From the floor to the bottom of the anti-cavitation plate is just a touch under 17". From the floor to the bottom of the "v" on the boat is just a touch over 17".

The motor is in the top holes.

Do I need to raise the motor up a couple holes?

Thanks again guys - the help is truly appreciated.

-Rook

[QUOTE=rook-eye slayer;1410329]Hi guys,

thanks for the help, it's truly appreciated.

OK - here goes.

REW - I'm at whatever sealevel Minneapolis, MN is at (or within 100ft)

I've included a couple pictures so you can see what I'm dealing with as far as bottom of boat to anti-cavitation plate differences.

I am also looking at the water level line and thinking the motor is too low. When I put the throttle down, the back end of the boat acts like it is getting "sucked" into the lake and it takes a bit for the boat to get on plane.

I bought a 15p prop and am going to try that this weekend, but am looking for recommendation on the motor height.

In the pictures, the boat is level bow to stern, and the motor is level front to back. Measurements are from the garage floor.

From the floor to the bottom of the anti-cavitation plate is just a touch under 17". From the floor to the bottom of the "v" on the boat is just a touch over 17".

The motor is in the top holes.

Do I need to raise the motor up a couple holes?

Thanks again guys - the help is truly appreciated.

-Rook[/QUOTE]

Raise it up one at a time until prop doesn't grip the water anymore and then drop it a hole. You find you can only raise your engine so high with a aluminum prop before it blows out.

Rook...I am just happy you brought another Merc to Lake Wissota, there are a few of us on this site and on that a lake. WI Pride lives on.

[quote=jkonop;1410353]Rook...I am just happy you brought another Merc to Lake Wissota, there are a few of us on this site and on that a lake. WI Pride lives on.[/quote]

JK - Wissota is great during the week. Frankly - i'd love it if the skiers and tubers went elsewhere - but that'll never happen.

I moved the motor up two holes, and now it measures out just where it should. Haven't gotten onto Wissota again as my boat partner (wife) isn't real keen on driving or backing up the trailer - and with no docks in the water at the landing - you gotta have two skilled people unless you want to get your feet wet.

However - we did get out panfishing yesterday with the kiddos - some nice success. Managed to catch a nice gill that measured up at just under 10" and just a hair under a pound. Was fun to wath the 4yr old bring that in on an ultralight rod.

- rook

On Water Testing Complete - amazing results
 

Hi Guys,

So I finally made the time today to get out on bigger, safer water where I can do some extended runs and really dial in the changes I made.

Changes:

Moved motor from top hole to middle hole (moved motor up 1-1/2" basically)
Purchased a 15p prop

Here's what we came up with:

[U][B]Original Setup gave me this:[/B][/U] (motor as low as it could go, 17p prop)
Top speed 34 mph at 5,000rpm WOT
zero hole-shot, bow shoots straight up in the air 15 second to get on plane

[U][B]Motor moved up 2 holes, 17p prop:
[/B][/U]Top speed [B]44[/B] mph at 5700rpm WOT
improved hole-shot, bow still rises quickly, about 7 seconds to get on plane

[U][B]Motor moved up 2 holes, 15p prop:
[/B][/U]Top speed [B]42[/B] mph at 5900rpm WOT
amazing hole-shot, comparatively almost no bow rise, about 3 seconds to be fully on plane


I want to thank the guys that gave me some ideas, as well as the rest of you who have posted all along on other threads. The ideas and the outcomes have been awesome. I'm going to stick with the 15p prop. The 2mph top speed loss isn't enough to make me run the 17p regularly. The hole-shot with the 15p is amazingly different - so i'm sticking with that.

Didn't get daring enough to take a picture of the anti-vent plate while on plane - but did look at it and it is right where it's supposed to be.

Thanks a ton guys,
Rook:cheers:

i run a 2010 lund fisherman with the same setup. 115 4 stroke and motor height. just curious which 15P prop you bought??