top speed ?

rdnk_4_lf

Petty Officer 3rd Class
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Jun 10, 2008
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93
i have a 1970 merc 100 hp on a 16 ft cheetah-xs fish-ski my friend ha a merc 150 blackmax xr 2 on a 17.6 ft procraft fish-ski what will the top speed on both boats be (he brags about his boat being so fast and im just wandering if with my bigger motor can i outrun him) we fish local tourneys and i used to have a 40 evinrude on it and it topped out at 31 mph ! what will this 100 do?
 

tashasdaddy

Honorary Moderator Emeritus
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Nov 11, 2005
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51,019
Re: top speed ?

no idea. sure sounds like you are over powered. if so some tourneys will not let you enter.
 

CATransplant

Admiral
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Feb 26, 2005
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6,319
Re: top speed ?

Too many variables. The only way to find out what your speed will be is to run the boat. A GPS rig will give you the most accurate measurement. If you were doing 31 mph with a 40hp, I'd guess you'll hit between 42-45mph with the 100hp. What's the max HP rating for your 16' fish'n'ski? I bet it's not 100 hp.

Can you outrun the guy with the 150hp? Who knows. Take 'em out to the lake and see.
 

rdnk_4_lf

Petty Officer 3rd Class
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Jun 10, 2008
Messages
93
Re: top speed ?

over powered ? one guy i know has a 140 on his 16 footer and the 40 wasnt toping out right the mechanic that currently tuning the motor said that if the motor runs right it should do 60 and the 100 is an i6 so it shou;d have power right
 

CATransplant

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Re: top speed ?

Look, you already wrote that your boat is rated for 85 hp max. So, with 100hp, it's overpowered. You can do whatever you want to do, but don't expect a lot of praise for running an overpowered boat.

As for speed in tournaments, it isn't necessarily something that makes for the winning angler. I came in third in a local tournament, running my usual 12' aluminum boat and 6hp outboard. It was the smallest boat, by far, in the tournament, and I caught all my fish within a mile of the launch, while the rest of the 40 boats were zooming around the lake. I didn't win, but I did pretty well.

As Tashasdaddy says, you may be disqualified from some tournaments with a boat that has an outboard that exceeds the boat's rating. Up to you. I'll leave the speed racing to others. I go to the lake to fish, not to race.
 

rdnk_4_lf

Petty Officer 3rd Class
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Jun 10, 2008
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93
Re: top speed ?

well this boat when we bought it had a 125 johnson on it so this 100 should be a downgrade right but i wish i could find an 85 it would go on the boat and i would keep the 100 just in case (thats what i was looking for when i ran up on this 100 because the 40 was way to small)
 

tashasdaddy

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51,019
Re: top speed ?

what does the plate on the boat say the hp rating is. that is what you have to go by, and the plate has to be on the boat. if you are above the top rated hp. you can create many problems for yourself. boat police can send you home, and not come back until you comply, with a ticket, if you have an incident, where someone is injured, get ready to give the everything you own. lawyers love these cases, and leave you boatless, and homeless.
 

Silvertip

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Sep 22, 2003
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28,758
Re: top speed ?

Seems to me your math is wrong. You said "i have a 1970 merc 100 hp on a 16 ft cheetah-xs fish-ski my friend ha a merc 150 blackmax xr 2 on a 17.6 ft procraft fish-ski what will the top speed on both boats be (he brags about his boat being so fast and im just wandering if with my bigger motor can i outrun him). Now where I went to school, 150 HP is bigger than 100 HP. So no -- your engine is not bigger and you won't outrun him with only 2/3 the HP in spite of the smaller boat (unless it is also very much lighter). I will also agree with the others that regardless what your boat had on it when you bought it, if the the tag says 85 HP max, that means 85 HP is the maximum LEGAL limit. Certainly there are lots of boats out there with engines larger than the rating for the boat. That does not make it safe or LEGAL. As mentioned, have an incident and someone else will own your stuff whether you were at fault or not. In this day overpowering a boat is economic suicide.
 

Kev144

Petty Officer 2nd Class
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Oct 16, 2007
Messages
159
Re: top speed ?

if you want a race i can always bring out my stv with a 300 merc ;)
 

steelespike

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Apr 26, 2002
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19,069
Re: top speed ?

Seems to me your math is wrong. You said "i have a 1970 merc 100 hp on a 16 ft cheetah-xs fish-ski my friend ha a merc 150 blackmax xr 2 on a 17.6 ft procraft fish-ski what will the top speed on both boats be (he brags about his boat being so fast and im just wandering if with my bigger motor can i outrun him). Now where I went to school, 150 HP is bigger than 100 HP. So no -- your engine is not bigger and you won't outrun him with only 2/3 the HP in spite of the smaller boat (unless it is also very much lighter). I will also agree with the others that regardless what your boat had on it when you bought it, if the the tag says 85 HP max, that means 85 HP is the maximum LEGAL limit. Certainly there are lots of boats out there with engines larger than the rating for the boat. That does not make it safe or LEGAL. As mentioned, have an incident and someone else will own your stuff whether you were at fault or not. In this day overpowering a boat is economic suicide.

Sentence is constructed strangely; He meant that his new motor is bigger than the 40 he was running.
I'm wondering about the sentence where it appears the mechanic says the 40 can do 60 mph.??
 

bassman284

Commander
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Jun 24, 2006
Messages
2,839
Re: top speed ?

yeah, if the 40, properly tuned can run 60 mph, the 100 ought to be able to do 90-100. Assuming it doesn't sink the boat at launch.
 

CATransplant

Admiral
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Feb 26, 2005
Messages
6,319
Re: top speed ?

yeah, if the 40, properly tuned can run 60 mph, the 100 ought to be able to do 90-100. Assuming it doesn't sink the boat at launch.

I don't believe there is a prop for a 40 that will enable that kind of speed, even if you could turn it at 5000 rpm. Bogus.
 
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