Prop and Engine Performance

joe7670 · #1 11-08-2009, 09:55 AM

So I ran the 150 Opti with Mirage Plus 48-19838 15P.

I was able to get 5400 RPM at 38-39 MPH.

Does this sound right given that I'm reading that once broken in the motor gives a little more or should I be trying the 17?

spareparts · #2 11-08-2009, 10:24 AM

something doesn't sound quite right about those numbers, I would have guessed a little better performance, but I'm an optimist, I allways guess too high. Wonder if the motor is a little low on the bracket. Ferm? some input here!

Skools Out · #3 11-08-2009, 10:33 AM

i agree spare sounds low on speed numbers, i was figuring 42 to 44 with that setup and those rpm's

THEFERMANATOR · #4 11-08-2009, 03:05 PM

The speed numbers do sound a tad low for a 150 OPTIMAX as that is a strong 150. Then again though I don't think the MIRAGE is an ideal prop for speed on a V-20. It is a very efficient prop with alot of bite to it which is good for offshore, but that large diamtere can actually cost you up high. I know my HYDRA lost a tad on the top end with my MIRAGE copy, but it gained alot at cruising. I would say a REV4 or ENERTIA would be a better match. Also from looking at your videos I would say don't be afraid to trim it up some more for top speed. You were running pretty flat in them and it looked like your engine was at a neutral to negative trim in them when you ran it up. For max speed you want to get the engine as high as you can without the engine cavitating or the bow blowing over. Check your engine height first as that can change alot of variables right there. If you are going to be doing alot of slow speed's and cruising offshore I would keep the MIRAGE, but otherwise I would reccomend a REV4 or ENERTIA to try.

captpete13 · #5 11-08-2009, 06:30 PM

I'm using a Merc Laser 2 on my boat. It works great. I wouldn't rule that one out either.

THEFERMANATOR · #6 11-08-2009, 07:01 PM

http://www.propgods.com/content/propellers.aspx

This will give you a basic idea of what MERCURY's props do. Check your engine height first, and if that is good see if you can find a 15 pitch ENERTIA. You may actually need a 17 pitch with it though, and remember that every prop will have a different engine heght it likes. Some like to run high and cavitate a little, and others have to be buried in deep all the time. I would think with the bracket though you would want a sternlifter as bow lift would be a problem on a sloppy day.

When checking your engine height you will need 2 people. One person drives and the other goes back and looks at the engine. You want to be able to see the caviatation plate just a little bit as a good starting point and go from there.
Like this

joe7670 · #7 11-08-2009, 10:04 PM

OK, you guy are too far from here. I would need someone that knows how to run the boat and trim it or freakining take a pic. of the cavitation plate.

The numbers specified are with me running the boat and trimming to what I think is adequate.

The videos taken are with my cousin trying to run the boat... has no clue on triming or much of anything. Can't even run the camera right while i'm running the boat.

I am curious to see the cavitation plate while underway but can't manage to do that properly while driving. lol

I can tell you one thing, the motor is about 3/4" high based on the requirements for motor height with set back.

Sound like it may take one more trip to get the answers I need?

On the trimming, it's not as easy to notice proper trimming with hydraulic stearing. On teleflex it seamed easier to me.

THEFERMANATOR · #8 11-09-2009, 12:56 AM

If you still have the engine hook just raise it up one more hole and try it. You'll know right away if it's too high as it will try and blow out coming on plane, or you will hear a buzzing sound when you trim it. When trimming for your top speed run, you want it trimmed to the point that the bow feels like it's airborne and almost jumpy. When I get em trimmed out high for top end runs and feels like it's trying to take off on every wave. your numbers still aren't bad for that boat and engine combo as it sits, and the MIRAGE will give you goo cruise numbers offshore. It isn't a top speed prop though from what I have found, it actually seems to work better on heavy tanks. I put one on a SEARYA 250 cuddy cabin and it made that boat fly compared to a regular stainless prop.

RidgeRunner · #9 11-09-2009, 07:57 AM

Joe, I had a 200 merc carb on the 20 cc for a while. It would turn a small diameter Quicksilver 17p past redline to 6100 and when I put the 17p Mirage it brought the rpm back to 5800. If you were not heavy when testing with the 15p sounds like a smaller pitch or diameter may help. IMO Prop testing should be done at high speed, trimmed out all the way. If you get to the redline with a light load it should be pretty close to perfect. I am pretty sure they build in some break in time in the computer on the Opti, you won't know what you have until you get past break-in. But I am not sure how many hours that takes or what the computer is doing during this time (I expect it isn't seeing max timing at WOT)
How does the boat sit in the water with the bracket?
I misread the first post. It should definitely turn the 15p

joe7670 · #10 11-09-2009, 08:37 AM

Actually, it's very possible that the electronics limit something cause there is a "Break in" period of 120 minutes on the guages. I'm down to 60 minutes or so.

I added a picture of how the boat sits below. It sits a little lower that it used to in the back. Not that I ever had it in the water but just basing on the prior water line. I'm talking maybe 1/2" lower, nothing crazy.

Sounds like i'm going to have to go out on one more trip to get out of break in mode, get better pics and maybe take a friend that knows how to drive or take pics. After that trip I may have more info.