NEED SOME HELP TO MAKE MY BOAT GO FASTER!! pls help!

[hirk]

Raise the jackplate so the center of the propshaft when level is2 1/2 below the pad,you are having to overtrim to get 5100 giving you a bad running attitude and you only get 4500 when trimmed down showing the case is too deep. Raise it and the prop will free up and turn more r's without over trimming and throwing a rooster which you dont want.Thx for the vote of confidence Ernie but Im sure you know more than I have forgot lol.

[walleyemen]

the prop to pad should be 3.5", this is generally a industry standard,and the wot rpms should be 5500 to 5700 rpms.that seems to be alot of prop for that 115, i,d try a 4 blade 19p, also does it have the vent plugs, i played with my stratos 21 ss extreme for almost a year before i got it right, i,m running a 2004 johnson 150 hp, 56 mph at 5500 rpms, 14.25/19p 4 blade cyclone prop,

[JamesG]

http://www.mercurymarine.com/propellers/prop-selector first place i check for the correct prop. I'm not sure on the jackplate setup as I dont have one but it does seem like the prop may be sitting a little low. Just to compair, i have a 16.5ft lowe aluminum boat with a 90 mariner, running a 23" pitch aluminum prop and I max out, light load, cold air at 45mph and I think 5350-5400rpm. If i were to change to ss i'd probally go with the 22" lazer 2 like you have. So if in the end you do change up your prop and get good results with a smaller prop, message me as i may be interested in the 22"

[Jackie]

just checked with the guy who installed the jackplate for me today, he said the jackplate was put 3.5" below pad...I guess I really should play around with the prop first before I raise the jackplate...gonna try the 20p 4 blade Composite Piranha Prop and see how that will do...

 

Thanks for the advise guys!

[Jackie]

Waynechute, what's vent plugs? and what does it do?

[aplumma]

I am not sure you are going in the right direction with a composite prop... The reason that a Stainless steel prop is better than an aluminum prop is it does not flex under load as easily. Going to a composite prop that is not as stiff even as aluminum will allow it to flex and it loses the cup and pitch to a certain extent. They are usually used on lower horsepower rated motors were they have less of a load on them. I have a 150 hp on a 1989 Ranger boat and their is roughly a 4 mph difference between my SS and my aluminum prop due to the lack of flexing of the SS prop since both props have the same diameter,cup and pitch. Personally your next step just might be to contact the company that makes the boat and get there input on what they feel is a good match up or visit a bass tournament in the area and see what they are using on the same set up. Checking with a few local marinas/repair places some have a loaner prop program where you get to try the prop for free to see which one is the right one to buy. Since performance is what you are looking for you will find that all of the go fast racing and bass master rigs all use Stainless Steel props not because they are shiny but because they are the correct answer.

 

 

Art

[davey buoy]

I am not sure you are going in the right direction with a composite prop... The reason that a Stainless steel prop is better than an aluminum prop is it does not flex under load as easily. Going to a composite prop that is not as stiff even as aluminum will allow it to flex and it loses the cup and pitch to a certain extent. They are usually used on lower horsepower rated motors were they have less of a load on them. I have a 150 hp on a 1989 Ranger boat and their is roughly a 4 mph difference between my SS and my aluminum prop due to the lack of flexing of the SS prop since both props have the same diameter,cup and pitch. Personally your next step just might be to contact the company that makes the boat and get there input on what they feel is a good match up or visit a bass tournament in the area and see what they are using on the same set up. Checking with a few local marinas/repair places some have a loaner prop program where you get to try the prop for free to see which one is the right one to buy. Since performance is what you are looking for you will find that all of the go fast racing and bass master rigs all use Stainless Steel props not because they are shiny but because they are the correct answer.

 

 

Art

 

However Art more expensive and less forgiving than a aluminum prop when hitting a rock

[hirk]

That composite is meant to be a spare dont waste your time trying it the blades flex it wont get you where you wanna be.Raise the plate 1" and run it without over trimming.Your prop doesnt have plugs,they are to fine tune holeshot if its bogging or over reving getting up.

[GBW]

Just curious Geoff, but high 50's seems really fast for an 18.6 boat with only a 115 pushing it.

 

Are you measuring your speed with a speedometer or is that reading coming from a GPS ??

 

There can be quite a difference between the 2 and a speedo is very often way off.

the speed'o Lew as it tends to hit 61MPH so this is why I said high 50's. I've raced a guy who has a speed boat (SVT) and a GPS and I asked him where he started to really take off from me and he said 54MPH it about where I topped out. The boat is Northstar scorpion 185

[Skipper D]

When you eye up the bottom of the boat , Who low should the prop sit below the bottom of the boat ? The top of the blade on my prop lines up with the bottom of the boat , maybe an inch lower at most , sound right ??

[lew]

the speed'o Lew as it tends to hit 61MPH so this is why I said high 50's. I've raced a guy who has a speed boat (SVT) and a GPS and I asked him where he started to really take off from me and he said 54MPH it about where I topped out. The boat is Northstar scorpion 185

 

Thanks Geoff, that's a good speed for that boat with a 115

[aplumma]

However Art more expensive and less forgiving than a aluminum prop when hitting a rock

 

You are correct the SS is more money and since it is ridgid it will break rather than bend. You got to pay to play when you are in the speed game. When I am down here the waterways have less humps and shoals so the SS is great. When I come up North I change to the aluminum prop. because of the lay of the land and my lack of knowledge of the places I fish.

 

 

Art

[kickingfrog]

I thought you got rid of the prop altogether? Man I can't keep you two straight.

[jedimaster]

Your numbers give that a prop slip of 20%, thats pretty high.

The theoretical speed is 51mph for a 2.07 gear ratio, 22 pitch prop, and 5100 rpms.

 

If you are not able to trim up enough you can add a wedge on you motor/jackplate. If your boat isn't able to trim up enough that could help you to also increase your rpm's as you will be getting more of the boat out of the water.

 

With a 22 pitch prop, and 5500 rpms, your theoretical max speed is 55mph. I would think you should be able to get your prop slip down in the 10% range getting you around 50mph...

 

Just for some info high 50's with a 2.07 gear ratio and a 22 pitch prop, your motor would require around 6000 rpm's. The theoretical max speed at 6000 rpms is 60 mph, add in prop slip your gonna be into you high to mid 50's...

 

A boat CAN'T go faster than the theoretical max speed. You can't have negative slip. Its not possible. as in PERIOD. End of story. Unless you also have a jet engine pushing you. But at that point your prop would be slowing you down.

 

A prop is essentially a screw in the water. Given the angle of the screw (pitch) and the speed its spinning, it can only move through the water so fast. There is always some slip, caused by hull drag, wind resistance, water resistance on the prop, prop flex will also have an effect, losing you a few degrees f pitch with an alluminum prop at full speed etc... This is referred to as slip.

 

For an efficient hull, and setup in a bass boat your looking at around 10% slip. An souper duper Allison might down down into the 5% prop slip range under the right conditions. Anything better than 10 percent is great, less than that and you can usually do some work.

 

You at 20% prop slip right now so you have some work to do.

 

And btw do your speeed with a gps. Water based speedo's are crap at best.

Edited April 8, 2012 by jedimaster

[craigdritchie]

Okay, since no one else has, I'll bite.

 

To the OP ....... why do you need to go faster? And, exactly how fast do you need to go?

[jedimaster]

Going faster means you can cruise slower using less fuel. An efficient boat is cash in your pocket. at 20 % slip he is throwing cash out the back of the boat even at cruising speeds.

[walleyemen]

It,s not a matter of going faster as it is in having the motor running at its best, if Jackie can trim down and essentually loose no speed then its slipping, kinda like doing 60mph in your car at half throttle and punching it and gaining no speed or just even spinning your tires, lots going on but not going anywheres,if the motors workng to hard and not doing what it should or labouring to achive what it needs then your just killing the motor!

[aplumma]

I thought you got rid of the prop altogether? Man I can't keep you two straight.

 

 

Well actually I have 4 boats a 10ft pond crawler, the Jet drive outboard, the ranger bass boat and the 28ft Marinette. I go from plastic to Bronze wheels between the 4 of them and my gas bill per month is in the hundreds but that is another story....

 

 

Art

[Terry]

Okay, since no one else has, I'll bite.

 

To the OP ....... why do you need to go faster? And, exactly how fast do you need to go?

 

why do men have a man cave

why do men have motorbikes and cars that can break the national speed limit in first gear.......I could go on but

 

it's a bass boat

 

 

I have a fishing boat old full windshield..just a regular boat and a 90hp on it and a kicker motor and I go faster then he does with his bass boat with a 115

of course he needs to break the 50mph....

if not paint it pink and put stick-on flowers on it and leave it at home one week a month for the Menzies ....LOL

 

but that's just my opinion

Edited April 8, 2012 by Terry

[Jackie]

I'm aiming at around 50 to 55mph... I'm only getting 40 mph on gps. I just want the boat to run at its full potential...I understand that rangers are build for stability and not speed, but a 115hp with jackplate and ss prop on a 16.5ft bass boat should be running more than 40mph if set up right...

Edited April 8, 2012 by Jackie

[Jackie]

why do men have a man cave

why do men have motorbikes and cars that can break the national speed limit in first gear.......I could go on but

 

it's a bass boat

 

 

I have a fishing boat old full windshield..just a regular boat and a 90hp on it and a kicker motor and I go faster then he does with his bass boat with a 115

of course he needs to break the 50mph....

if not paint it pink and put stick-on flowers on it and leave it at home one week a month for the Menzies ....LOL

 

but that's just my opinion

 

 

 

 

Lol yea exactly!

[misfish]

I'm aiming at around 50 to 55mph... I'm only getting 40 mph on gps. I just want the boat to run at its full potential...I understand that rangers are build for stability and not speed, but a 115hp with jackplate and ss prop on a 16.5ft bass boat should be running more than 40mph if set up right...

 

 

 

Ok, you just blew my mind.Why do you have a jack plate on a 16.5 ft bass boat?

 

Like I said.My 18 with a high 5 ,115,and mounted right to the boat,went faster then that.

Edited April 8, 2012 by Misfish

[woodenboater]

Just curious as I've never run a boat that fast and it'd probably scare the beejeebus outta me but I'm wondering, does the jack plate result in any loss of energy/force transmission since the motor isn't bolted 'directly' to the transom ? Is it sponging any push resulting in less efficient use of rpm etc ? Sorry if this question doesn't make sense.

 

I'm just a low horse tiller guy, until I win the lottery

[Jackie]

Ok, you just blew my mind.Why do you have a jack plate on a 16.5 ft bass boat?

 

Like I said.My 18 with a high 5 ,115,and mounted right to the boat,went faster then that.

 

 

Exactly ur 18 with 115 no jack plate is goin faster than my 16 with jack plate... That's why I'm not satisfy with the speed it's getting right now... A jack plate might not do much for a 16, but it wouldn't do any harm...would it?

[jedimaster]

There are lots of reasons for a jack plate.. Especially on a small boat. Every extra inch makes a difference. When you trim the motor fully do you porpoise at all? I think your going to need to wedge the motor a bit. This is pretty common. I had to do the same with my stratus. I am a little bit confused what the problem is though. Are you saying the bow isn't lifting up high enough, or it won't go down enough? If you are under power and you are unable to trim the motor up up and raise the bow then you have a mechanical issue. I mean you motor should trim up right out of the water.

If you have too much prop your likely to not even be able to get out of the water. How is it getting up on plane? I would raise the motor. Start with the prop shaft at 2 inches below the pad. When you drop to a 4 or 5 blade prop your doing this to get out of the hole faster not to raise your top end.

 

What pitch prop were your running on that high 5, what was your top speed and gear ratio?