115hp Mercury Optimax Question

[Pony]

Recently purchased a new to me 2005 Lowe Fishing Machine 175s (17.5ft long w/ 92" beam). On it is mounted a 115hp Mercury Optimax of the same year. Current prop is 19 pitch. I assume I should be at 5600-5700 rpm WOT....

I was finally able to take it out on a larger lake today where I could open it up and test it out. With my dad and myself in the boat along with 3/4 tank of fuel (full is 27 gallons) I was able to get 5400rpm when trimmed out. If I stayed trimmed down I was more like 4100-4200. GPS speed was 36mph.

Is this running as efficiently as I can run it? Should I have to trim out to get max RPM? Should I try and get that extra couple hundred rpm? and finally is 36mph decent for that set up??

The prop on there is aluminum....what would I see with a SS??

 

[Pony]

Re: 115hp Mercury Optimax Question

Bump....here is a video of my motor for reference.

 

[jestor68]

Re: 115hp Mercury Optimax Question

Your rpm range is 5000-5750.

Running your numbers through various simulators indicates a good SS 17 pitch will raise your rpm up to about 5700 and reduce your slip(presently like 21%) to about 11%(hopefully); and thus actually gain in overall performance, including a 2-3 mph increase in top speed, depending on how low we can get the slip percentage. Example; 10% would equal 40 mph.

Something like a MIchigan Wheel Apollo would be a good choice.

The Mercury Vengeance (SS) equivalent is the 13.125 X 17.

In reference to your video; if that was a full throttle acceleration, not impressive.

The 17 pitch SS will fix all that.

 

[Pony]

Re: 115hp Mercury Optimax Question

Your rpm range is 5000-5750.

Running your numbers through various simulators indicates a good SS 17 pitch will raise your rpm up to about 5700 and reduce your slip(presently like 21%) to about 11%(hopefully); and thus actually gain in overall performance, including a 2-3 mph increase in top speed, depending on how low we can get the slip percentage. Example; 10% would equal 40 mph.

Something like a MIchigan Wheel Apollo would be a good choice.

The Mercury Vengeance (SS) equivalent is the 13.125 X 17.

In reference to your video; if that was a full throttle acceleration, not impressive.

The 17 pitch SS will fix all that.

I didn't really "put the hammer down"......at 21 seconds is where I trimmed back out and picked up the extra RPMs. I had suspected I might be over propped.....and sort of figured I should be 40+ in that boat even with that load.

Is the Aluminum prop flexing a bit with that HP?

This is a big change for me......going from an 88 25hp Johnson.

 

[Pony]

Re: 115hp Mercury Optimax Question

May seem like a noob question, but what would be the advantage of a 3 blade vs 4 blade SS prop?