How Fast Will be BOAT suppose togo!

[longstand]

Hi again.

I have a Twin OMC (GM) V6 3.8L Engine

it said each engine is 170HP

My boat is Big.. if you search online for my boat you will see what i have.
everything on the boat is DRY no wet spot anywhere so i dont have to worry about extra DRAGG

I always wonder. i have a Twin engine, how fast can i really go.

i ask this because i seen a boat about the same size as my boat and it was really really going FAST and it only had One Engine. and i belive he has my kind of a Sterndrive. and its an older boat just like my.

Anyone?

 

[Chaparralboater]

Re: How Fast Will be BOAT suppose togo!

Hull design, props pitch,boat weight, engine ratio ect.. All probably matter in speed.

 

[glengold]

Re: How Fast Will be BOAT suppose togo!

there is much more to performance than just weight (wet vs dry). hows the bottom of the hull?? as said prior, what about the props?? I have a lower pitch prop for wakeboarding, higher pitch for light loads/max speed. there are so many variables. He could have his tweaked for speed, but load it up for a day of watersports and it will have trouble planning.

Look at the manufactures rating, in my case it was rated with a smaller motor (48hp vs 55hp) but in perfect condition so i don't get what the manufacture says i should....

Hope this helps...

 

[marlboro180]

Re: How Fast Will be BOAT suppose togo!

Longstand- where you been??? Good to see you back- whatcha running for props?


Getting WOT rpms proper?

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

Longstand- where you been??? Good to see you back- whatcha running for props?


Getting WOT rpms proper?

I been Home.. LOL. i was LayOFF form Welding at the ShipYard here in San Diego from a company call Nassco..

Beside thats Its great.. iam bored again so Here iam back on my boat. haha

15x17

I assume 15 is for PICH and the 17 is for ????

 

[marlboro180]

Re: How Fast Will be BOAT suppose togo!

Put that up in the prop section- that seems like small props to me- Diameter first, then pitch. Are they cupped?


Are you getting to wot? ( redline)

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

CUPPED? what is that.. LOL..

 

[marlboro180]

Re: How Fast Will be BOAT suppose togo!

CUPPED? what is that.. LOL..

A quote from boatus:- ( they say it better than I can :redface

Cupping

Many of today's propellers incorporate a cup at the trailing edge of the propeller blade. This curved lip on the propeller allows it to get a better "bite" on the water, resulting in reduced ventilation and slipping, and allows for quicker acceleration, or "hole shot," in many cases. A cupped propeller also works well in applications where the motor can be trimmed so that the propeller is near the surface of the water. The cup will also typically result in a higher top end speed.

Chinewalker may chime in on this! But are you getting proper WOT RPMS????

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

Great INFO MAN..

the last time i got the boat out. it seems like the Engine was running to hard just to keep the boat moving.

the way i imagine it. my prop just spin and spin and it hardly push..

do i need a bigger prop? . i just want to be able to put some gas and go instead of putting to much gas just to barely move..

i will try to CUPP my prop first and see what happen. if it dont work i buy a new one..

 

[marlboro180]

Re: How Fast Will be BOAT suppose togo!

Great INFO MAN..

the last time i got the boat out. it seems like the Engine was running to hard just to keep the boat moving.

the way i imagine it. my prop just spin and spin and it hardly push..

do i need a bigger prop? . i just want to be able to put some gas and go instead of putting to much gas just to barely move..

i will try to CUPP my prop first and see what happen. if it dont work i buy a new one..

Ok, I remember from a while ago that we have a bit of a language barrier, but no worries bud! Have you checked the prop(s) for being spun??- a spun prop goes round and round, but cannot push the boat fast as the hub in the prop has been damaged by something, and the prop shaft is spinning inside it faster than than it ( the prop) is really turning. - Think of this- a worn out manual tranny clutch on your truck, going up a hill pulling a heavy load...

the analogy here is that the worn out clutch equals the worn out/ damaged hub in your prop(s)

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

I remove both of the prop a year ago and i did check out the prop.. i assume the HUB is the inside (Center of the PROP). if it is then i think its good, i did not notice anything that is missing or broken in the center of the prop (HUB) .

I also check the shaft where it locks into the prop. it don't seem warn-out.

ye man. thanks.. we do have a language barrier. or maybe its just education barrier.. iam at college here in san diego at ITT TECH. and iam a 3.5 GPA so far. maybe when my english Semester i will be a better speller and hopefully learn grammar

 

[marlboro180]

Re: How Fast Will be BOAT suppose togo!

Well, your English is better than any of the other languages that I do not know bud! Education- who knows... I live the life of the auto - didacticism, look that one up!

This is why I am thinking spun prop(s)

the way i imagine it. my prop just spin and spin and it hardly push..

Could be a bad coupler too,,,

I hope I am not barking up the wrong tree here with the spun prop(s) , but you still have not said what your WOT RPMs are.... Please advise. 4800 rpm, 35 mph , or knots , for example?

 

[Z71Man]

Re: How Fast Will be BOAT suppose togo!

The thing about the 3.8 is that it's a good engine....if it's turbocharged....

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

Well, your English is better than any of the other languages that I do not know bud! Education- who knows... I live the life of the auto - didacticism, look that one up!

This is why I am thinking spun prop(s) Could be a bad coupler too,,,

I hope I am not barking up the wrong tree here with the spun prop(s) , but you still have not said what your WOT RPMs are.... Please advise. 4800 rom, 35 mph , knots , for example?

WOT= Wide Open Trouble

.. how do i get this..

I assume the maximum RPM of what it show on the Gauges?

or i should put my timing gun with DIGITAL RPMP GAUGE on the #1 spark plug and open it WIDE to the max and tell you the MAX RPM my engine could go...

is that rigth?

 

[superbenk]

Re: How Fast Will be BOAT suppose togo!

WOT = Wide Open Throttle - it's the speed your engine is turning (RPMs on yrou tachometer on the dash) when you have the throttle all the way down & the boat is going as fast as it possibly can.

They want to know the following:

1. What does the tachometer say when you're going as fast and as hard as your engine can go?

2. What speed does the speedometer say? If you have a GPS that you can check your speed with, that's a lot better as it will be more accurate.

To check for a spun hub in a prop, get one of those silver markers at the hardware store & draw a line across the middle of the prop so that it starts all the way on the edge of the center where it's metal & crosses over the nut in the middle & keeps going all the way to the other side where it's metal. Do this on both your props, then take it out in the water & run it to get the WOT above. When you're done, look at your props again & see if the line is straight all the way across the center of the propeller still (just like you drew it). If it is, your prop is fine, if it's not straight, it means the outside metal part of the prop is loose on the inside rubber part & you have a spun hub. The rubber inside the hub is spinning around faster than the propeller is.

Good luck!

 

[Chaparralboater]

Re: How Fast Will be BOAT suppose togo!

WOT is wide open throttle... With your throttle all the way down while driving on the water see what your boats rpm will hold at.. Like doing a top speed run. Remember that number. Then look on your engine for an ID plate that tells you specs about your engine, it should say what the highest amount of rpm your engine should be putting out..then take your WOT rpm and match it to your engines required rpm. Your probably above what your engine is asking for which also means your props are too small. Don't jump the gun but you probably need a larger prop ( higher pitch prop )..

Make sure our engines sync, make sure the bottom of the boat is smooth ect. Hope some more info helps

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

WOT = Wide Open Throttle - it's the speed your engine is turning (RPMs on yrou tachometer on the dash) when you have the throttle all the way down & the boat is going as fast as it possibly can.

They want to know the following:

1. What does the tachometer say when you're going as fast and as hard as your engine can go?

2. What speed does the speedometer say? If you have a GPS that you can check your speed with, that's a lot better as it will be more accurate.

To check for a spun hub in a prop, get one of those silver markers at the hardware store & draw a line across the middle of the prop so that it starts all the way on the edge of the center where it's metal & crosses over the nut in the middle & keeps going all the way to the other side where it's metal. Do this on both your props, then take it out in the water & run it to get the WOT above. When you're done, look at your props again & see if the line is straight all the way across the center of the propeller still (just like you drew it). If it is, your prop is fine, if it's not straight, it means the outside metal part of the prop is loose on the inside rubber part & you have a spun hub. The rubber inside the hub is spinning around faster than the propeller is.

Good luck!

Thats good advice thank you and your so clear.. i will do that.

thank you very much

 

[Philster]

Re: How Fast Will be BOAT suppose togo!

Put the boat on the water. When it is warmed up, take it someplace safe and then push the controls forward and give full power.

The goal is to get to the fastest speed you can (by GPS readout or speedometer).

When the boat is going as fast as it can go, check the speed and the tachometers for both of your engines' revs. You need to come back here with those numbers and please tell us about any other strange things that happen.

DO NOT do any of this with the boat out of the water.

 

[longstand]

Re: How Fast Will be BOAT suppose togo!

OK great. i will do that.. i will take the boat out maybe at the End of this month. and i will Update my Thread.

all i need is to adjust the Fuel-Mixture and we are all good for testing

 

[180shabah]

Re: How Fast Will be BOAT suppose togo!

The thing about the 3.8 is that it's a good engine....if it's turbocharged....

Don't even go there......