HOW ACCURATE IS SPEEDOMETER

[TIM MARKING]

I HAD MY NEW NX750 OUT THIS WEEKEND WITH A 115MERC ON IT WITH A 22P SS LASERII PROP AND AFTER I GOT IT BROKE IN (WHICH WAS FUN) I WAS ABLE TO GET 57MPH ON THE GAUGE. PRETTY GOOD I THOUGHT. ONCE I HAD MORE GAS AND A COUPLE OF KIDS WAS ABOUT 55MPH

 

[Staci Matheis]

Uh uh. I'm not gonna tell him.

I'll let someone else break his bubble.

Uh uh. Not me.....

 

[Dennis Ciccaglione]

Well some are close... But most are as accurate as wetting your finger & putting it in the wind...



Get GPS..



Dennis

 

[greg hall]

My PT175 w/75 Merc would show 49 to 51 on my speedo I just got my GPS hooked up & was dissappointed to see the GPS was reading 44.2 mph at the fastest,speedo was reading 50,yes the speedo reads faster.

 

[TritonGlenn]

Boat speedometers are put there for your viewing pleasure... not so much to accurately tell you how fast you are going. If you don't want to get a GPS for it (I would), you may want to check into some of the newer GPS speedometers. I believe Gaffrig and a few other top gauge manufacturers make them. Stock boat speedo's, such as most Teleflex speedo's, are not accurate at all.

P-A-T-929

 

[Kevin Jaquith]

I found with my NX750 the speedo is out 8-10 mph. I ran mine on GPS and my top speed with 115 is 52.7mph. Hope this helps

 

[Bryan McDonough]

Mines off anywhere from 1 to 68mph depending on how fast i'm going.

 

[TOMMY RICH]

And Greg...I'll be the one to burst yours

Your not doing 44 on a 175 with a 75. My 185 with 90 GPS's @ 45 with myself and half tak of gas

 

[Texas Transplant]

On my Stratos, it is very accurate up to about 40-43 mph. After that, not at all.



Tex

 

[Greg J.]

I know that the last time I was out I was really clipping across the water (PT175 w/50hp), into the wind, against the waves...then I looked down at the speedo, which read about 12mph, lol. To add to the exhiliration of the ride I had to turn my ball cap around backwards to keep from losing it. A strong wind blowing in your face, with water splashing around you adds a great sense of "speed", lol.

 

[Staci Matheis]

You guys are BRUTAL!

Nine posts descrediting his speedo.....

If this were football.....

Wouldn't that be considered "piling on"! LOL!!

 

[Steve Rizza]

I GPS'ed mine with Treps handheld.

The speedo read 34...the gps read 34.2.

 

[Tony Hughes]

Last weekend in santee, my nx750 with 115 was running 55 per speedo and 50 with gps. That is with full tank, two hefty fisherman, and all gear. My motor is new also and the prop is 24p laser2.

 

[William Birkett]

I think greg could do that fast and more with his PT175 with a 75... I have gps'd mine over 45... It is possible with the right conditions...



Tight Lines

 

[TrepMan]

As Steve mentioned i've GPS'd mine and his, my speedo is the opposite of everyone else!! At 30mph on the GPS my Speedo only reads 24 mph!!!

 

[Larry Harp]

When I first bought my boat it would show it topping out at about 32 to 35 mph, which is about right for a PT-185 with a 50 horse. The pilot tube got broken and after I replaced it it will only top speed at about 28 or 29. I certianly hope I'm going faster than that but I'm sure it's not much faster.



Harpo

 

[Staci Matheis]

What is the make and model of your factory finder?

You may have to install a new base that would come with the finder/GPS.

 

[greg hall]

TEE my GPS may be wrong come up to the upper chesapeake bay & we can race!

 

[William Birkett]

Can I race too... I think the three of us would be a close race...



LOL



Tight Lines

 

[Scott Hammer TOXIC]

Mine showed 38mph when my shorts and shirt flew off showing my thong........sure hope nobody got it on film.



TOXIC

 

[Greg J.]

These guys will race you

 

[Jim B]

Tee, i dont doubt what greg says one bit. A pt 175 with a 75 horse motor have better power to weight ratio then a 185 with a 90. The 175 is a much lighter hull by about 300# and a 15 hp difference isnt much.

 

[Tony Hughes]

Tmar,

I have a lowrance lms385 gps/finder combo. Plugs right in and uses same mounting braket as stock lowrance unit on nitro. It has a base map with moderate detail. I bought a pod transducer for the trolling motor and a new mounting braket to mount the stock unit in the front of the boat.

 

[Don Wilhelm]

Boat speedos are notorious for being incorrect. GPS is the most cost effective way to get a closer reading, but even they can be sketchy. I often talk to people who make great claims about thier boats performance, but are disappointed by the hard numbers. Prop pitch, gear ratio, and engine rpm are calculated to give MAXIMUM theoretical speed (many claims are well over the max speed). Hull efficiency (prop slip) is factored in to give a round about top speed. The same formula can be applied to a car(if you know the gear ratios and tire diameter), with much more accurate results (no prop slip to deal with). Thats not to say that a boat can't or won't go as fast as stated, it just means that it can't if the operator is not over revving the motor.

 

[greg hall]

I bet I can get 45 to 46 on the right day in calm water 44 was in a slight chop w/21P SS prop,I think my 19P would have gone faster,the SS prop made all the difference in the world when I switched to Stainless prop. I had A 19P first & then went to a 21P,the 19 reved too much but had a awsome hole shot,the 21 handles better but the hole shot is ok & is more stable at speed.

 

[William Birkett]

Mine came with an aluminum 23P... I thought about going SS but I fish in some shallow water sometimes... and didn't want to hit a stump with SS...



Tight Lines,

 

[TOMMY RICH]

O.K. You wanna' race? You better have your ducks in a row because the SS Tracker is FAST!

Greg...check the Tracker site too...your estimated speed is 42-43 on a good day. So is the 90 with the 185.

I'll smoke you out of the whole which in turn will win just about any race.

Maybe we'll have to settle it some other time

 

[William Birkett]

Hmmm.... MyD is pretty darn fast outa the hole too... But like any good boater, I may talk a mean game here, but on the water me and my boater education certificate play by the rules... Sorry for the let down on racing... But in my mind Greg and I would beat you in a very close race... (so what is the point in racing... LOL)



Take care friends,



Tight Lines

 

[Mini]

Tox,



What are you doin running a Ranger/Rude combo? LOL



Mini

 

[TOMMY RICH]

According to Tracker my rig is only 30 lbs. heavier with 15 more ponies

 

[Jim B]

My bad i looked at the wrong numbers on the website. Still 15hp isnt a lot all things given. more hp dosent always mean more speed, for example my old boat was a 16' champion with a 115 evinrude on it, my buddy had a ranger sport r72 with a 130 johnson on it at that time. Both boats weighed in at ~1200# and i was over 5mph faster then he was and it drove him nuts because i had 15 less hp. We both turned 22" rakers. Why was mine faster? I have no clue, it just was.

 

[TOMMY RICH]

Slicker hull too...That Sharkhide smooths the surface

 

[William Birkett]

Beg me all you want... I still am not going to race... We both know we have faster boats... It is after all not about going faster... It is about each of each getting to our fishing holes in a timely manner with the most time to enjoy our sport... If I cruise on up to my favorite hole and someone is there I just keep enjoying driving my boat to my next honey hole... with a smile on my face just because any day on the water is better than every day at work...



Tight Lines to all my firends...

Bill

 

[TrepMan]

OK i'll race ALL of you in my 175 with my 40 !!! Forget Prop pitch, gear ratio, engine rpm, and Hull efficiency (prop slip) - I only weigh 137lbs so i'm WAY faster!!! LOL ANd if I turn sideways I have ULTIMATE Trepper Efficiency!!!

 

[TOMMY RICH]

You got us Trep...Noone can compare to your skinny butt! LOL

 

[greg hall]

Bill that's why I went with a SS prop I bent 4 aluminum props on logs every time just idleing. I would barely touch somthing & it would bend,already this year I have hit the bottom & stuff the SS is unscaved,SS is the way to go,if you hit something hard enough to break your lower unit it would'nt matter what your prop was made of.

 

[William Birkett]

Greg,



I guess I have been un-nerved by the talk of what hitting something with a SS prop would do to the lower unit... I am careful in skinny water and don't want to hit anything hard but if i hit something I have been lead to believe that it is better to hit it with an alum prop. Anyone elses thoughts???



Tight Lines

 

[Greg J.]

Thinking that maybe the aluminum prop would absorb some of the impact (while bending), and not transfer it to the lower unit?

 

[William Birkett]

That is the way it was explained to me... Much cheaper and easier to replace an alum prop versus the whole lower unit...



Tight Lines,

 

[TIM MARKING]

Thats why I have insurance on my boat, unless you have your prop reworked everytime you get a ding in it, because the cavitation that is caused by the prop not being true causes damage. SS prop does not get all those little dings in it.

 

[greg hall]

the 4 times I hit my aluminum prop it was mangeled I was lucky to get to the ramp & I mean I was idleing! the 2 last times it bent it cost $75 a pop to repair it so I just bought SS,the 2 other times I was wide open & that was my fault,the SS is way more durable & the performance gain is very noticable,maybe not on a 50hp or smaller but 75 & up go w/SS,I'm very carful now but the upper bay can be very bad for props!