need alittle more speed.

[99 Sierra]

I have a 84 laser ltv that runs 70. I'm trying to hit right around 80 and was wondering what it takes. the boat is rigged with a 1989 merc 175 I ordered a bobs lwp and am planning on having the heads shaved. Will this be enough to hit this mark? is there anything else I can do to the motor? Any info or thoughts will be great. thanks

[staylor]

....with no changes in weight or running capability of the hull/lower unit you will need to go from 175 hp to about 245 hp to go from 70 mph to 80 mph. You will need a lot more than shaved heads to do this. I'd consider looking at buying a 225 hp engine as a starting point and modding the 225 a bit.
Doug

[moomba]

The LTV I just sold ran 91 with a stock 2.5 200 with glass reeds with a 200 lower and a bobs cone and LWPU. If you dont have a jack plate you will need one.

[Maple Leaf]

Start with optimizing setup, You didn't say what prop you were running, RPM, Or Prop shaft height. Need more info :)

[99 Sierra]

the motor is on a 5.5 cmc manual jpat 3.5 inches below the bottom,the prop is a 14.5x26p merc chopper. i get 70.6 mph by myself at 5300 rpm tryed a 24p chopper and it pegged the tach at 6000. I ordered a bobs lwp for my stock LU the get the motor higher.

[99 Sierra]

I hoping to get a little more speed with my motor with a few mods the motor is 20 years old but runs like a champ 120-125 on all six i have yet to do a leakdown test but for what she is the motor runs really strong. I think my setup really needs some tuning for sure even if i can get to 75 that would be cool. Also I think I need to try a differant prop tried a 14.4x24 and turned at least 6000rpm tach stops at 6 and lost topend. the 14.5x26 picked up topend but can only turn it to 5300rpm maybe shaving the heads will let get me up to 5800 or 5900 not to sure though

[afr]

you dont have to have more hp unless your racing
i would just leave that 20 year old motor alone and work the set up
you need hight rpm prop gear weight to be all in sink then it will run faster
you get messin with the motor to much and next thing you know your buying racing fuel and staying on the beach most of the day cause you cant afford to waist the gas or put time on the motor
and since it is a older motor i would wing it up if it was mine cause i wouldnt care if i blew it up
well i dont care if i blow any of um up cause you dont get to much invested like a drag motor or something on a budget just dont work

[Charger200]

Get a Bobs cone on their jack her to the moon and hold on i suspect you will see 80 or just shy with the addition of the jackplate. choppers like to be run high i suspect you will hit the limiter with it if you get her jacked up.

If i run my motor 3" below i would see about a 12mph+ difference on top end.

[rdkvector]

Get a Bobs cone on their jack her to the moon and hold on i suspect you will see 80 or just shy with the addition of the jackplate. choppers like to be run high i suspect you will hit the limiter with it if you get her jacked up.

If i run my motor 3" below i would see about a 12mph+ difference on top end.
:iagree::iagree::iagree: The problem is setup, not h.p. work on optimizing that first. If you're looking for 80, you'll need a 28p prop and turn it 6k.:thumbsup:

[velox]

....with no changes in weight or running capability of the hull/lower unit you will need to go from 175 hp to about 245 hp to go from 70 mph to 80 mph. You will need a lot more than shaved heads to do this. I'd consider looking at buying a 225 hp engine as a starting point and modding the 225 a bit.
Doug

To go faster by adding more HP to an existing engine is butting your head against the wall. Power requirements go up as the cube of the speed ratio.
The ratio from 70 to 80 is 1.43. The cube of 1.143 is approx 1.5.
175 HP times 1.5 is a little over 260 HP.
The only chance you have, is if you setup is off now and is improved.
Tilt, boat balance, weight, streamlining, engine and prop selection are all part of the equation. To go 80 with you boat and lower unit would be very difficult. I agree that you need to go to a 225 and work from there!

[99 Sierra]

I think I will mess with the setup first I should be able to get a little more speed. as for the 225 my buddy just bought a ckeckmate exciter with that size and he runs 80 and that boat is 350 pounds heavier. I think after setup is right if needed I will go up in horsepower. most of the LTV I've seen on here with power like that go fast than I need.

[Charger200]

To go faster by adding more HP to an existing engine is butting your head against the wall. Power requirements go up as the cube of the speed ratio.
The ratio from 70 to 80 is 1.43. The cube of 1.143 is approx 1.5.
175 HP times 1.5 is a little over 260 HP.
The only chance you have, is if you setup is off now and is improved.
Tilt, boat balance, weight, streamlining, engine and prop selection are all part of the equation. To go 80 with you boat and lower unit would be very difficult. I agree that you need to go to a 225 and work from there!

That equation is only relevent to a boat that has already optimised every once of power then engine can provide.

If he is 3.5" down running a stock lower unit and a 26chopper 70.6@5300 he is not even close to an optimal setup. I would guaranty that 80is possible with this power.

Go out and run an engine on any V or tunnel V 3.5'' down and see what speed you end up with. then go back to your optimal set up and compare speeds.

If this thread is still goin in june i will humour you with documenting this on my personal boat .

Ive never driven or set up an ltv but i can tell you ive never seen a boat that's engine is located 3.5'' below pad and is optimally set up.

If like moomba said the ltv he sold ran 90 with a 2.5 200 then i would think that even though the 175 is a 2.4 and makes a lil less torque that 80 is in the equation.

Spend you money on a cone first prop second and dont forget a good jacket cause it will be night and day difference once you run that engine high. You 26 will most likely be all over the limiter and you will litterealy feel like you flying.

I went from having my charger with a 2.4 200 on the transom to the 245 with 6'' plate. With the engine pulled up high the boat was smooth and felt like it was flying. You got alot of height to gain which will equate to alot more speed

Just my .02

:cheers:Jay

[velox]

That equation is only relevent to a boat that has already optimised every once of power then engine can provide.

If he is 3.5" down running a stock lower unit and a 26chopper 70.6@5300 he is not even close to an optimal setup. I would guaranty that 80is possible with this power.

Go out and run an engine on any V or tunnel V 3.5'' down and see what speed you end up with. then go back to your optimal set up and compare speeds.

If this thread is still goin in june i will humour you with documenting this on my personal boat .

Ive never driven or set up an ltv but i can tell you ive never seen a boat that's engine is located 3.5'' below pad and is optimally set up.

If like moomba said the ltv he sold ran 90 with a 2.5 200 then i would think that even though the 175 is a 2.4 and makes a lil less torque that 80 is in the equation.

Spend you money on a cone first prop second and dont forget a good jacket cause it will be night and day difference once you run that engine high. You 26 will most likely be all over the limiter and you will litterealy feel like you flying.

I went from having my charger with a 2.4 200 on the transom to the 245 with 6'' plate. With the engine pulled up high the boat was smooth and felt like it was flying. You got alot of height to gain which will equate to alot more speed

Just my .02

:cheers:Jay

What I said does not in any way disagree with what you said.
Note I said he had to improve his setup if it was not correct.
What I said was to increase speed with HP, it power required is the cube of the speed ratios. That is correct. If he changes setup that is changing his drag to power ratio. At that new drag-power ratio he would then follow the power-cube formula.

[99 Sierra]

I was wondering do them torque tamers work or are they not worth it.

[DerStream]

Its all in the set up as most guys on here have stated. The LTV hull is a very fast hull even with only 175 hp on it, unless it is waterlogged, I am not sure if you have the foam coaring still in the boat or not, but i also understand that you could not jack the motor up because you did not have a LWP on the gearcase, but now with the LWP you should be able to run even or just above the pad and the boat should be like a new boat aslong as she is not water logged. Also have someone or yourself, weld your cone on, or atleast tack it in plase, you will eventually lose it if you just epoxy it on.

Also a buddy near me got a LTV that was in storage for years and he took his 2.5 200, bobs case & offshore tossed it on the boat, set the leading edge inline with the pad, and the boat was all waterlogged, he went out and ran high 80's, now its under resto.

[99 Sierra]

the boat was completely redone last winter floor transom etc. before the redo the boat was water logged as hell. got the lwp and installing on lower unit now going to tack weld it like you said

[imq707s]

Start with optimizing setup, You didn't say what prop you were running, RPM, Or Prop shaft height. Need more info :)

Yep....start messing with engine height, and try some different props. :thumbsup: