Help choosing a prop

[stratos275xl]

Ok. I posted yesterday but after re reading I realize I wasn't making clear what I need. Ok so I have a 94 stratos275xl with a 95 mercury blackmax 150xl 2.0 with oil injector removed and im mixing 50:1 . from what iv gathered the dry hull weight is 1200# correct me if im wrong but motor is in the 400# vicinity . usually only run around 15gallons of fuel "About all I can afford". and 3 batteries.and light gear load.i weigh 195 my partner that fishes with me around 220 and is with me 99% of the time. it is snowing and cold here so I done just a quick measurement and the motor is approx. 3 1/2 to 4" below the pad I have "hijacker" manual jackplate not sure of offset around 4" I would guess. the prop I have on it is precision turbo ss 14.4x24p. best top speed run was gps speed of 51 to 52 at 6k. in lows 40s at 5500 now In not 100% sure if tach is correct because of the motor swap with all original electronics. Now I have heard of same rigs with same motor/prop pitch doing hi 50s to some breaking 60. .So my question is do you think I could gain anything with a better quality prop and if so what pitch and brand?the prop on it has sum nicks and small bent places but nothing major and no vibration.And its not blowing out trying to come on plane. But iv heard the precision turbos aren't really that great of a hi po prop.the current holeshot isn't something to brag about but I can live with it and may have a little to do with 50:1 mix and a huge No wake zone to have idle thru. seems little better after warms up but not much.So any recommendations on prop would be appreciated and maybe an estimate of what it should do. Also I do not have a WOT speed vs rpm because can pull 6k in drop of hat and have to back off it and that's not trimmed out all way.But like I said not 100% sure on tach.

 

[HT32BSX115]

Re: Help choosing a prop

But like I said not 100% sure on tach.

Howdy,

You're wasting your time without a KNOWN tach.

 

[stratos275xl]

Re: Help choosing a prop

Well the boat is new to me and most my other boats were smaller with small pitch props so the tach may be rite.because i dont know what normal speed and rpm with this size boat and motor.it does float at low rpm little but settles after 5k for .thats reason i asked if anybody had close to same set up to have a baseline of what i can and cant do prop and speed wise.main question was what would be a good replacement for whats on it.i just didnt wana loose anything by just quessing and buying different brand 24p .i was hoping someone would chime in with same set up and say theyr getting x amount of speed at x amount of rpm so i can have something to at least compare mine to.

 

[Mi duckdown]

Re: Help choosing a prop

stratos. Still not clear. got a headache reading your first post. not sure of anything???

 

[stratos275xl]

Re: Help choosing a prop

I guess its time to move on to another site.everyone wants to just be sarcastic and not help a fellow boater and fishermen appranantly just because i do not have a degree in typing or how to word things.i was just trying to explain everything so nothing was left out .i do not set behind a desk honing my typing and posting skills and this was my first time posting or even joining a forum.i do wana say thanks to the guy who helped me get info from my serial number.not trying to be an *** just dont like getting beatdown because i asked a question the wrong way.esp when you look at some of the goofball boating rookies asking dumb questions and people helping them without sarcasm.im out.

 

[steelespike]

Re: Help choosing a prop

I hope you will stick around long enough to see if you get any help.,
Guessing your gear ratio at 1.85 At 6000 rpm with a 24" prop 10% slip speed would be around 66.
My first guess from your description is the tach is wrong. You need to confirm the tach/rpm.
At 52 the rpm would be around 4700. Keep in mind there are a couple of guesses involved here.
The guys are just trying to figure out what your saying so they can help.
I don't know what it is about your post but I too found it difficult to follow and I've been on here a long time.
Maybe if you answer just the questions in the stickys at the top of the prop forum it would help.

 

[stratos275xl]

Re: Help choosing a prop

I appologize for the rant.and the confusing post.like i said new forums and posting all together.but you just gave me the answer i was looking for.according to what your saying the tach is not even close so its time to replace the tach and then test run and monitor speed n rpm and go from there.i just thot my tach was little off and the prop was horrible if that makes sense. Big thank you for clearing things up for me.

 

[jestor68]

Re: Help choosing a prop

I think there might be a couple of issues here, because according to the Mercury prop computer, you can't do what you're doing.

Meaning; your numbers through the computer indicate a Mercury Tempest Plus 22" is supposed to turn about 5300 rpm @ 53 mph.

So, if you can spin a 24" to any high rpm, you got some serious slippage going on. Possibly because your motor is too high.

Are you clear on how to measure your pad to prop shaft dimension?

 

[Silvertip]

Re: Help choosing a prop

Hold on Dude. You are getting all wrapped around the axle here. It was SUGGESTED that the tach is wrong based on a PROP CALCULATOR. While the tach may indeed be wrong, don't dash out and buy another only to find that it reads the same. PROVE the one you have is wrong by using a shop tach. Yes - I know, you don't have one. You then have a choice to barrow, rent, buy or steal one. If you stick your head under the console and look at the back of the tach you will find a little dial with numbers like 4P, 5P, 6P etc. Note the current setting and then move that dial "carefully" back and forth several times and then reset it to the original number. Now see what happens to top end RPM. If it's the same, verify that the tach is actually set to the correct position. Then be a little more patient and understanding. We can't see your boat and have to decipher what people say. Many folks have trouble verbalizing what the issue is and leave out important information but include gobs of information that has no bearing on anything. We want to help but we don't like to have to spend post after post trying pull information from posters. If you are asked a question or told to do something, then do it and come back with the result. Only then does the problem get resolved.

 

[stratos275xl]

Re: Help choosing a prop

I leveled the trailer and trimmed all way in.measured.from.lowest point of the bottom of.boat directly under the drain plug.then measured center of hub to ground then divided the difference.is that correct? Now my garage is gravel but its level and thats why i gave the 1\2" variable.i agree with you it doesnt sound rite.and i thot shoulda been alot faster esp at 6k .

 

[stratos275xl]

Re: Help choosing a prop

This may just be rambling to all of you but i have been building and racing mx bikes for many many years.thats why just by sound it doesnt sound like turning 6k.on my bikes at end of powerrange they stop pulling plain and simple.if ideal range on the merc is 5 to 5500 max.the boat should.not pull like a frieght train if im showing 55 to 5700 then open it up.cuz from 5500 till past 6 it pulls harderd than anywere in the other rpm range.i never went past 6100 on tach but was definatly still wanting to pull hard which in reality at end of its powerband it shouldnt .

 

[jestor68]

Re: Help choosing a prop

The reason I asked about the pad to prop shaft dimension is because I thought I read in an earlier post by you that things seem OK until a certain rpm/speed(4000 rpm?), then when you give her more throttle, the rpm climbs rapidly all the way to 6000.

But: a 24 pitch prop (1.87 gear ratio) going 53mph figures out to 4361 rpm.

If you were turning an actual 6K rpm, a 10 % slip speed would be 66 mph.

Since your pad to prop shaft dimension is in the ball park, I would verify the tach. Sometimes just cleaning the terminals on the back of the tach helps.

 

[stratos275xl]

Re: Help choosing a prop

Im slowley learning how to word stuff so everybody can understand so bare with me guys.lol.what i meant in that was the tach will.fluctuate 1k up n down untill u get it above 5k.like at idle sometimes it jumps to 2k .the prop seems to have good bite.its not blowing out that i can tell at any rpm.and thanks for input on precision prop several people have told me try a laser 2 i heard the mercs like those.i have a higher end multimeter that has rpm and is actually pretty acurate.i use it to tune chainsaws alot.i will try it just for the heck of it to see what its showing soon as crappy weather is gone.

 

[jestor68]

Re: Help choosing a prop

The hot ticket is the Tempest Plus. Don't get too carried away with pitch.

I invite you visit the Mercury Marine web site and look over the tests of the 150 on boats like yours. They give detailed results, including what type/pitch prop used and even engine mounting data.

 

[stratos275xl]

Re: Help choosing a prop

Ill have to check into that.Thanks for the info.hopefully can get it.straightened out this weekend.Just trying to get ready for fishing.much rather fix it now.instead of wrenching on boat when fishing is good. Cant really complain much cuz i traded 2 ar15s for the boat when people started going nuts.thinkn they were gona totally ban them.