new prop or not

[clint243]

I have a new to me 1995 statos 280 fish and ski with a evinrude 150. this motor starts right up idles fine pulls hard to wot ...comes out of the hole like there is no tomorrow...here is my qustion ...on gps it runs approx 47-50mph with the wind and a good 45mph aginst the wind....however I can only get about 4900-5000 rpms...this boat is running a 14 1/2 x 20 raker stainless prop.LIke I said this boat is new to me and I didnt get to run it when I bought it due to the transom being rotten ....but the po said it would do about 50 on the water....I am using this as a more fishing than skiing boat which is the opposite of what they used it for ...they used it for a ski seat and ski boat...like I said this boat runs great starts great revs great ...the only thing I can think of is that it is over propped for what I want ......and as far as coming out of the hole....my best friend has a 21" pro craft bass boat with a merc 250 on the back ...I can litteraly smoke him off the line...like he is not there ....but after about 30 mph he reels me in and is gone .....I now this is not really a comparing apples to apples but more of an expination of how it comes out of the hole

thanks in advance guys

Clint

 

[1980Coronado]

Re: new prop or not

I have a new to me 1995 statos 280 fish and ski with a evinrude 150. this motor starts right up idles fine pulls hard to wot ...comes out of the hole like there is no tomorrow...here is my qustion ...on gps it runs approx 47-50mph with the wind and a good 45mph aginst the wind....however I can only get about 4900-5000 rpms...this boat is running a 14 1/2 x 20 raker stainless prop.LIke I said this boat is new to me and I didnt get to run it when I bought it due to the transom being rotten ....but the po said it would do about 50 on the water....I am using this as a more fishing than skiing boat which is the opposite of what they used it for ...they used it for a ski seat and ski boat...like I said this boat runs great starts great revs great ...the only thing I can think of is that it is over propped for what I want ......and as far as coming out of the hole....my best friend has a 21" pro craft bass boat with a merc 250 on the back ...I can litteraly smoke him off the line...like he is not there ....but after about 30 mph he reels me in and is gone .....I now this is not really a comparing apples to apples but more of an expination of how it comes out of the hole

thanks in advance guys

Clint

First....I've never caught fish going 50 mph

Second....What you describe sounds like a good running boat. You'll want that hole shot when you put two more buddies in the boat to go fishing with. With another 350 lbs in the rear of that boat you might be surprised that your hole shot just went away.

However, If the boat was "under propped" as you said, the rpm would be too high at wide open throttle (WOT). I do not know what the WOT rpm max is for your engine, but if you increase the pitch to get more top end, the rpm will reduce by 150-200 rpm per inch of pitch as a rule of thumb, given the same diameter, type, material, and mfg of prop. If you reduce the pitch to increase rpm your top speed may not change much, it may actually decrease, unless the motor is "lugging", which by your description of performance doesn't seem to be the case.

What you need to find out, is what the max WOT rpm should be for your motor and see how far off you are. You need to know the year, model and gear ratio of your motor. You may not be that far off at 5000 rpm. You may also have an issue with the motor that's not allowing it to reach max rpm, dirty carb, old plugs...etc...that's also something to check. The fact that your buddy having a 100 hp more blows by you at 30 mph is not an indicator that your prop is wrong or anything is wrong for that matter.

 

[clint243]

Re: new prop or not

Mark,
Thank you for the reply ...I guess I have my terminology backwards....as far as the motor goes I will ool into what the gear ratio is but I do know that the motor is a 1995. The max rpm is 5500 from what I can find ...and I can get about 4900-5000 depending on the direction of wind and travel...

As far as my buddy blowing past me ..I fully expect that I was just trying to give an idication of the hole shot this boat has...LIke I said this is a new to me boat and I am kinda basing how it runs in the water off of my olde boat which was a 1995 bayline Quantum f/s...it was a bit smaller and and the hull desing was way different than this one ...it had a very shallow hull where this one is a much deeper v...it however had a merc 150 black max and it would turn about 5700 rpm wot with a top speed of about 55....however I had to add a hydrofoil to get it to plane out much quicker.....I do again thank you for the reply ...and any info I get will undoubtedly help me ....also I cant find much info about this raker prop....all I now is the po said it was rather expensive and it is in very good shape ....

thank you again

Clint

 

[metriccrescentwrench]

Re: new prop or not

LIke I said this boat is new to me and I didnt get to run it when I bought it due to the transom being rotten ....but the po said it would do about 50 on the water....

The transom is repaired now isn't it? When (if) the transom was repaired what else was done? What I'm getting at is I'm wondering if there's the possibility you've got some rotten stringers and/or some waterlogged foam. Rotten stringers often let the hull deform at speed, costing you several mph. And of course waterlogged foam will weigh you down, again costing top end speed.

If you're positive the boat doesn't have issues, have you checked all your throttle linkage adjustments to be sure the butterflies are opening all the way at WOT? Also, check maximum timing advance.

Something doesn't add up. For starters a 20 pitch prop sounds reasonable for your boat/moter combination. If hole shot is as good as you say you ought to be able to rev right on up close to redline (which is the way you want it) without difficulty (I think it's around 5800 rpm but won't swear to it).

 

[1980Coronado]

Re: new prop or not

No problem.....if your motor has a max WOT throttle rpm of 5500 and you're at 5000 (and you trust the tach!)...then I'd say you could reduce the pitch an inch or two and see what happens.....as long as you know your getting everything out of the motor....throttle opening up all the way...carbs clean...plugs good...etc. It's hard for me to say what will happen to your top end though because your going the wrong way in pitch to increase top end...think about it this way....when you reduce the pitch the prop has to turn more revs to go the same distance as a larger pitch...so..that said it becomes a diminishing returns thing....when you increase the rpm your getting more out of the motor, but your going less distance per rev.....so at some point you will go slower with an increase in rpm (due to pitch reduction).....it's something you will just have to experiment with if you're trying to tweak the last 2 mph out of it.

Have you run a compression test?

IMO, 500 rpm low on the top end...and you're satisfied with the hole shot...I wouldn't mess with it...if you told me you had a hard time getting out of the hole with three guys in it...I'd tell you to reduce the pitch and get the rpm up.

Edit....I agree with the above post...something doesn't add up.....good point about checking for extra weight due to water in the foam. I went at this assuming you repaired the transom Also assuming you're trimming the motor up while on plane to raise the bow?

 

[Dhadley]

Re: new prop or not

I would look into the accuracy of the tach first. A 20 Raker would seem to be a good choice for that hull. It's a bit confusing when you say the holeshot is great but you are so far off on top end. That motor will turn 6000 easily if set up right. As for smoking your buddy off the line, I have no doubt. Your motor has tremendous bottom end power and revs quick. Mercs are known for not having much for low end punch.

Anyway, it would seem we're dealing with more than a prop change here. To gain 800-1000 rpm with only a prop change we'd be looking at something like a 15" prop and that's just not right. You haven't mentioned where the jackplate is set, or if you have one. Let's check the tach first and then the sync & link. Especially if the tach is a Faria.

 

[1980Coronado]

Re: new prop or not

I would look into the accuracy of the tach first. A 20 Raker would seem to be a good choice for that hull. It's a bit confusing when you say the holeshot is great but you are so far off on top end. That motor will turn 6000 easily if set up right. As for smoking your buddy off the line, I have no doubt. Your motor has tremendous bottom end power and revs quick. Mercs are known for not having much for low end punch.

Anyway, it would seem we're dealing with more than a prop change here. To gain 800-1000 rpm with only a prop change we'd be looking at something like a 15" prop and that's just not right. You haven't mentioned where the jackplate is set, or if you have one. Let's check the tach first and then the sync & link. Especially if the tach is a Faria.

first I'm not an outboard guy...but, Clint said his WOT max is 5500 for the engine.....if that is accurate, we're talking about 500 rpm here not 800-1000.....unless you know for a fact that motor is rated for 6000. In which case something is really amiss with the motor...or as both you and I wondered...is the tach accurate?

 

[Dhadley]

Re: new prop or not

That motor will live longer if it is capable of 5800-6000 rpm with an average load. The rev limiter is at either 6200 or 6700, depending on which pack it has. 5500 as the top capable rpm is border line lugging. Those are great motors but are not very tolerant of higher than normal combustion temps.

 

[1980Coronado]

Re: new prop or not

That motor will live longer if it is capable of 5800-6000 rpm with an average load. The rev limiter is at either 6200 or 6700, depending on which pack it has. 5500 as the top capable rpm is border line lugging. Those are great motors but are not very tolerant of higher than normal combustion temps.

I'm skeptical about the 5800-6000 rpm spec. I just did a internet search and found some WOT rpm specs for the 1995 Evinrude 2 stroke....both the Intruder, and standard 150 hp motor list a min WOT of 4500 rpm, and max WOT of 5500 rpm. Clint posted that his engine spec is 5500 max WOT rpm....I'm not sure where the 5800-6000 is coming from. Again.....if this motor is in-fact capable of 6000 rpm, then something is wrong with the boat, motor, or tach. Hes running close to 50 mph at 5000 rpm, and is happy with the hole shot....if the motor was lugging, he wouldn't be happy with the hole shot. This motor is not performing like it's 800-1000 rpm shy of max WOT spec if it's running 50 mph at 5000 rpm IMO. Somehow the rpm spec needs to be confirmed one way or the other.

Clint....The only way to get closer to the engine's specified max WOT in your case is to either reduce pitch or reduce diameter and test it.

 

[1980Coronado]

Re: new prop or not

I just went thru several prop selectors on-line for this engine and type of boat. One thing I noticed about the suggested sizes....all of the 14 1/2" diameter props were 19" pitch. For what it's worth....it seems to make sense..... Your' running a 20" pitch in the same diameter and are slightly below your max WOT rpm of 5500 assuming the tach is accurate. Reducing the diameter to 14" and staying at 20" pitch or staying at 14 1/2" diam and reducing pitch to 19" seems to be the answer.

 

[clint243]

Re: new prop or not

Wow guys thanks for all of the help ...this is one reason this is why I use this forum ....it was a life saver whaen I did the transom repair... now to answer a few questions ...I did check the stingers and the foam when I did the transom repair ...they checked out good...the compression on the motor was 118-122 on all of the cylinders ...so that tells me we are good on complression ....this motor starts right up and idles perfectly ...when I went to but it I met the po at her house and it was 28 deg that day and the motor had not been started in 3 weeks...we hooked up the muffs and a few pushes of the choke and she fired right up into a steady smooth idle....I think the motor is running great but I can and will do a link and sync as soon as I get the service manual in ....

I am very happy with the way this boat runs...dont get me wrong ..I was just thinking there might be a bit more in her is all ....but i will do a bit of trial and error with different props if I can get my hands on any .....living out here in the desert has its drawbacks ....but anyway thank you guys for the help and I will see what I can do on my end


Oh and this boat has no jack plate...if it will help I can get a picture of where the motor sits on the boat ...for all I k now it may be to low in the water ....

Clint

 

[1980Coronado]

Re: new prop or not

Sounds good....have fun playing with it.....post back with your results...I'd like to know what you figure out.

 

[Dhadley]

Re: new prop or not

If you have room try raising the motor some with the Raker you have. Those props like height and raising the motor will reduce drag. That will get your rpms up some without going to less pitch.