150 Optimax propping question

[Deerdog]

Hello all,<br />I am pretty much new to this section. I blew up a Force 150 last summer and replaced with a 150 Opti. Man is that thing sweet.<br /><br />I started with a 21 pitch prop but think I need to drop down to a 19 b/c the 21 will max out at 4900 rpms when the range is supposed to be 54 to 5700 rpm according to the book. <br /><br />The boat was doing 56 at 4900 (by GPS) which is more than fast enough. Oh the boat is an 89 20ft Arriva. The prop was a Merc Laser II. <br /><br />Would appreciate any opinions.

 

[JB]

Re: 150 Optimax propping question

Prop topic.

 

[gatorred]

Re: 150 Optimax propping question

wind it to tight they tend to not like it, if it say's 5700 in merk book i wouldn't run it hour's on limiter <br /><br />if it came form lake-x it would take it <br />Mercury test lake where racing stuff tested

 

[walleyehed]

Re: 150 Optimax propping question

You "May" have to go to a 17P to get to the top of the RPM range, which is where it should be...<br />You're well below max torque at 4900, so going to a 19 may add about 600 or so, maybe a tad more.<br />It would be nice if you could test/borrow a 19 and see where it gets ya...I think you'll see around 5400-5500, but you really need to be at 5700-5800.<br />If the engine is mounted in it's lowest location, we may be able to gain a couple' hundred by raising it and getting close with the 19..it just depends on the prop and how the boat reacts.

 

[LubeDude]

Re: 150 Optimax propping question

Originally posted by gatorred:<br /> wind it to tight they tend to not like it,

Walleyehed, your so nice!!! <br /><br />Wrong!!!! Especially with todays gas, youre much better off with the higher WOT RPMs. Plus, you will have a much better hole shot.

 

[imported_bjs]

Re: 150 Optimax propping question

what prop&pitch does mercury recommend?that's a good place to start.if your not turing in rpm range.you should go to smaller pitch prop.i will check with a buddy of mine i think he has a 19 pitch ss on his 150 opti.im not sure what dia.is or what kind but i will ask him.his boat runs good.

 

[bluewater19]

Re: 150 Optimax propping question

The mercury marine prop selector is usually way off.<br />I just went from a 1996 merc 75 turning an 18 pitch. To a 1997 merc 125.<br />According to the prop selector my Ideal pitch was now 28.<br />The new boat motor came with a 26 pitch laserII.<br />The laser only hit 4800 with the new motor Not the 5250 WOT that mercury suggested. I am turning a 24 pitch now just perfect.<br />That is 4" less pitch than the merc selector recomends.<br />My buddy has a 2005 115 and the prop selector said 19" so thats what his new boat came with.<br />It took a 16 pitch to get up into the recomended WOT range.<br /><br />Here is a link<br /><br /> http://www.mercurymarine.com/prop_selector <br /><br />It was real close with my glastron. I run a 25pitch and it says a little over 26" max<br /><br />Good luck

 

[walleyehed]

Re: 150 Optimax propping question

My dad's Glastron with an in-line 4 sterndrive will not even plane with the prop recommended for it...It's 5" off on that boat.<br />In testing props, I've found it is ALWAYS atleast 2" too much pitch, and in some cases, has been as far as 6" off.

 

[atticus3600s]

Re: 150 Optimax propping question

I think aabout 1 inch in pitch will get you an extra 200 RPM. so...<br />it seems that you shouls try a 17 pitch prop. A 19 pitch will probably get you around 5300 RPM WOT, and if the book says 5700 then you can drop down another inch or two in pitch.

 

[walleyehed]

Re: 150 Optimax propping question

mercury89, the 200 per inch goes out the window when we have an existing RPM of well below the torque curve...yes, the numbers would show that a 17 is in order, however, i've found by a fair amount of testing (and alot of guidance from Dhadley)that this is not the case when we are well below the target RPM. And, if we can try a 19 and get close, we can then customize the set-up to get a 150-200 RPM more with that prop. We want to set up for the prop, not prop for the set-up. Maximize what we have first, and obviously, the 21 is out of the question in this case...it's just way too low RPM to get all we need back.<br />Now, to back up on that statement, if we had a high-speed lower unit, a jackplate and some other performance up-grades, we might make a 23 Work, but that isn't likely what the owner wants, so we try and maximize with the first most logical choice.

 

[Texasmark]

Re: 150 Optimax propping question

Propping is a unique science; unique to your rig, in particular hull shape, weight, and engine size (also the engine's gear ratio....some as low as 1.69:1 and others as high as 2.3:1....does make a difference). You can't go to charts and come up with a reliable answer.<br /><br />If your hull is padded and you have power trim, you just added at least 400 rpm's to your existing rig regardless of the prop.<br /><br />Agree that you are lugging the engine and should run up at the top of the rpm curve. I have been running multi-cylinder Merc's for years, on padded hulls and they run quite smoothly at 6000 and I haven't lost a powerhead yet. So don't worry about your 5700. <br /><br />Matter of fact, I just bought another one, a 17' aluminum River Trail Brand with a 90 (2.3:1 gearbox) on it jacked up 1". This aluminum boat is padded, believe it or not and they are on the www. Check out their Lake Sport (it's featured at the top of the home page for Bass and Crappie boats. Really a honey. Make their own matching trailers too.<br /><br />When I bought the boat it had a Ballistic (Michigan wheel) 17" and it was just too shallow a pitch. The first time I goosed it, it popped my neck (hole in about 1 second) and it topped at 7 grand. Obviously I pulled her back fast, went home and got another prop.<br /><br />Second prop was a 21" and that pulled the revs down to 6200 and the top speed at 49+. (Engine is spec'd at 5250 to 5500). Couldn't stay there long as my eyes were wattering and it was hard to see, even with my glasses on. I like that combination and I'll stay with it....reason why below.<br /><br />Now a couple of pointers. I was running pretty much an empty boat, with just me, on a 40 degree day with low humidity; lake condition was glass smooth....optimum conditions for top end running....slight chop might have gotten me another mph. <br /><br />When it gets to be summer (heat and humidity) you will loose some of your top end (so says Merc and it's true). When you load up the boat with your buddy, half dozen tackle boxes and rods, cooler chest, and a live well full of water, you will loose some more. <br /><br />I don't have to run flat out all the time and other than for a short thrill I probably will do most running around 40 mph in the mid to upper 4k range.<br /><br />One last thing. With less pitch, you can throttle the engine much more easily to provide the speed you want. The boat doesn't want to run away from you like when you have it propped tight for high speed only. It doesn't run up on plane and you back it off, then it slows down (too much) then you add throttle and it's back up on plane and back and forth.<br /><br />So read what I said and if the 17 fills the bill, go for it. One thing you don't have to do. If the 17 is a bit shallow and she wants to run over the top end (revs), you don't have to run it up there. Grin.<br /><br />Merry Christmas,<br /><br />Mark

 

[walleyehed]

Re: 150 Optimax propping question

That's a mistake to go clear down to 17....That's usually everyones first thought...but it's not the most efficient.<br />Texasmark, I welcome ya aboard, and thought for a moment there, we had someone who understood it's ok to run a few hundred over the top recommended..but, your last comment shocks me...never "keep" lowering pitch to get RPM back....find the one a few hundred short, maximize the set-up and get're a few hundred above. Then, that boat will be, not only faster than yours, it'll be much more efficient at 4000RPM than yours will too..Bottom line, it will be a mistake to go right to a 17P.

 

[imported_bjs]

Re: 150 Optimax propping question

would a jack plate do anything?or im i way out in left field!!!!!!!!!!!!!

 

[walleyehed]

Re: 150 Optimax propping question

Jackplate is, in most cases, a good performance addition. If the customer wants to spend a little cash, we can make'r smoke so ta speak...

 

[Texasmark]

Re: 150 Optimax propping question

Hi again Walleye,<br /><br />Reading my response, I agree that, given what Deerdog said, a 4" drop seems a bit drastic. <br /><br /> But...... I don't know his rig nor the gear ratio's of the Force and Optimax, nor how he uses it. And, since propping is all about gears and moving a screw through a non solid medium, that matters as I'm sure you well know. <br /><br />I also agree that just dropping pitch for the sake of doing it may not be the optimum solution, but again that depends on the owner, the rig, and how it's intended to be used. <br /><br />For a guy that wants to load up the boat with the wife and kids and putt around on Sunday afternoon it's a quick fix.<br /><br />Maybe his original engine threw me....a Force. I don't associate them with high performance so I just assumed he was a Sundayafternooner. Grin.<br /><br />Mark

 

[Ron G]

Re: 150 Optimax propping question

I agree with Kenny from my own experinces if you get close you can tweak it with the setup to get ya there,and its amazing how much you gain or loose in the adjusting and its fun to.everboat is different thats the entire reason you just cant slap a prop on a motor and swap from one pitch to another ever pitch you try you may have to do some tweaking just my 2 cents.

 

[imported_bjs]

Re: 150 Optimax propping question

maybe you could find gear ratio that might help some i think to prop a boat you need a handful of props buy the one you like the best i know a guy who has two props one for water skiing the other for running around the lake. ofr top speed.

 

[walleyehed]

Re: 150 Optimax propping question

If you really give a Rats Butt about how your boat performs, you will want, by all means, to do any and all tweaking you can do to maximize your set-up, if you're not interested in tweaking, then you really didn't want the max potential out of your boat anyway.<br />I can safely say, after running, oh...let's say (for numbers sake)100+ props on the same boat, very few run the same. Now, YOUR Idea of the same and "MY" Idea of the same is likely going to be different..But, the props I started with, running 5700-5800 were mostly 17 pitch...with alot of playing and tweaking, I've greased another 5 inches of pitch, and have kept the 5700-5800. I've increased my speed by 12 mph, and yet I consider 1mph a good improvement, so, you can throw props at it and make it turn the R's you want...or, you can tweak what you have to turn the R's you "Need", or...you can go farther and tweak and test, tweak and test, etc, and increase speed dramatically, which increases fuel milage, again, dramatically...or just settle for what you have....do you really know what you have???? Do you care????<br />That's the difference.

 

[Texasmark]

Re: 150 Optimax propping question

Hey Ken dude.<br /><br />No rub intended dude, but props at say a conservative 250 bucks each, for high performance varieties, which is what you are/have to be talking about in this type of circle, dude, as we are talking about performance and all, equates out to about 25,000 dollars, US currency. Somebody has very deep pockets.<br /><br />And while I'm at it, you nailed me on the 17" suggestion, but if you would back up a half dozen replies, that's exactly what you recommended.............so what gives dude?<br /><br />Mark

 

[walleyehed]

Re: 150 Optimax propping question

The manufacturers SEND me props at NO CHARGE for test data...I test under controlled situations and send the documents back to the manufacturers, that way the Data is un-biased to any one manufacture.<br />Is "this" where I recommend a 17????? Read into it farther...<br />

You "May" have to go to a 17P to get to the top of the RPM range, which is where it should be...<br />You're well below max torque at 4900, so going to a 19 may add about 600 or so, maybe a tad more.<br />It would be nice if you could test/borrow a 19 and see where it gets ya...I think you'll see around 5400-5500, but you really need to be at 5700-5800.<br />If the engine is mounted in it's lowest location, we may be able to gain a couple' hundred by raising it and getting close with the 19..it just depends on the prop and how the boat reacts.<br />

And, BTW, some of the props I run are lab-finished and run around 1000-1400 for purchase...I get them for nothing..it's my payment for the several hundred gallons of fuel I go through testing them...