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Author Topic:   boat speed
grogden posted 08-08-2001 12:40 AM ET (US)   Profile for grogden   Send Email to grogden  
I have an 86 15 ft sport with an evinrude60.I was wondering what its top speed would be @5500 rpm using a 14x17 prop.It seems fast but I dont have a speedo or gps, my guess is around 40.If anyone has a similar setup I'd be curious what sort of results they've gotten
jameso posted 08-08-2001 08:40 AM ET (US)     Profile for jameso  Send Email to jameso     
I have a 15 with a 50 Everude,,, on a good day I can do 37/8 via GPS. I have the engine about 2" above the transom and run in the second hole. I had a 4" setback plate on the boat..improved the hole shot some but I did not like the static trim,, so off they came. The combination you have is a really good performing rig, I have thought of re-engining and get a 60-70 Hp with T&T but it is hard to justify,,,,just boy's toys! If you have more questions email me, Jim Armstrong
Bigshot posted 08-08-2001 10:12 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Is that the 2cyl or 3cyl 60hp? I had a 2cyl with a 12.?x19 SS and she would run over 40(42-43) at close to 6k. The 3cyl's I believe redlined at 5500 back then so you might want to jump up to a SS if you do not have 1. My 70 3cyl with a 13x21"SS would do close to 48 at around 5800 shooting a 5'tall rooster tail. Might be too much for the kids. Chine walked like mad and would scare the heck out of anyone who got in it, myself included.
SuburbanBoy posted 08-08-2001 02:33 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
My 15' will go about 36.5 mph, at about 5,200 rpm via GPS. To get up to 36.5, I have to tilt the engine quite a bit and suffer with twitchy handling. If I drop the motor a little, I can pull 34 mph. I have a 70 Tohatsu with a 4 blade Power Tech Stainless 17" prop, and a 4" setback bracket. The motor has about 20 hours on it, and I guess the total rig weight is about 1,200 - 1,300 lbs. The lower unit plate is about 1.5" above the bottom of the hull with the motor tilted down all the way. It would go about 34 with the stock 3 blade aluminum at 5,800 rpm. I am a little disappointed in top speed, but everything else is great.


skookum point posted 08-08-2001 03:01 PM ET (US)     Profile for skookum point  Send Email to skookum point     
Just for comparison, I have a 2cyl 40hp Evinrude on my 15. The prop is the stock aluminum 11-3/4 x 17. Cavitation plate is even with the bottom of the hull. With one person aboard I am getting 32mph (GPS) at 5400 rpm. Based on what I have read here I'm planning to raise the motor up one hole and see what happens. Still I'm really happy with the performance considering it is only 40hp.
Bigshot posted 08-08-2001 03:05 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
What is the redline on that? If it is overpropped you will suffer top speed but have a nice cruise. Your setup sounds perfect. Is that with just you? Maybe once she breaks in it will go faster. The best I ever did was at least 46.8 but I think it was 47.8 on the GPS.
MilwaukeeWhaler posted 08-08-2001 04:19 PM ET (US)     Profile for MilwaukeeWhaler  Send Email to MilwaukeeWhaler     
What's more accurate the transducer or my handheld GPS?
Whaler4me posted 08-08-2001 04:32 PM ET (US)     Profile for Whaler4me  Send Email to Whaler4me     
Bigshot, What motor was on your 15? I had a 15 with a 75 hp merc. on it and I know it went over 50. Used to chine walk like crazy and frightened me most of the time.

Grogden, I would say somewhere in the low 40's is about right.

triblet posted 08-08-2001 07:38 PM ET (US)     Profile for triblet  Send Email to triblet     
jameso, bigshot: was that knots or MPH. BIG

Milwaukee Whaler: GPS is more accurate, provided
you are doing more than two or three knots,
probably within .2 MPH now that SA is turned
off, more like .1 MPH if you have WAAS or DGPS.


SuburbanBoy posted 08-08-2001 07:49 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
BigShot, you may have asked me the question? The redline on my Tohatsu 70, 2001 is 5,850rpm. I may raise it up even more. It is very tough to get cavation until the motor is tilted quite a bit. The prop is a 13.5 x 17. Still, I was hoping for more speed....

Got a ride in my friends Cobalt, 55mph without trying. But then again, my investment is much smaller.


grogden posted 08-08-2001 10:05 PM ET (US)     Profile for grogden  Send Email to grogden     
thanks alot for all the replies, its cool to talk to people with similar boats.I dont know my redline for sure,I've run it at around 5500 give or take a 100.This is with 2 people weighing together about 360lbs,9 or 10 gallons of fuel.I have the pin on the lowest hole and it seems to get on plane quick enough, like 3 to 4 seconds without killing it and cruises flat.I haven't tried any other positions but I think it would just push the bow down if it were higher.Is this true? The boat and motor are an 86, which I got this summer second hand.It is my first boat and its alot of fun. One problem I have is that the previous owner was a bit lax in maintaing the boat.When I got it the fuel filter was full of rubber particles,which must have been from an old rotted fuel line.After I replaced it and the plugss alls Im finding more residue in the filter,what should I do?Drain and clean the tank?

jimh posted 08-09-2001 08:44 AM ET (US)     Profile for jimh  Send Email to jimh     
On a 15-Sport the fuel tank is external, so it should be a simple matter to drain and clean it. It might even be time for a new tank if the old one is a plastic tank.

It sounds like your Evinrude-60 does not have power trim. Moving the lower unit away from the transom will tend to raise the bow. This is referred to as trimming "out" or "up". The more trim up, the more speed, until you reach a point where the propeller begins to lose its grip. Try moving it out one notch at a time.

You can compute the speed potential of the prop using simple math, but you need to know the gear reduction of the lower unit. Your owners manual probably has that data. See my article on propeller basics in the REFERENCE section. URI:


triblet posted 08-09-2001 11:27 AM ET (US)     Profile for triblet  Send Email to triblet     
Also as you trim the bow up, the bow will
start to porpoise. On my Montauk that
limits the trim, not the prop's grip.

And it also starts to slam harder off the

I generally run it trimmed pretty much all
the way down on the ocean. Can't hit top
speed on the briney anyway.


grogden posted 08-09-2001 03:30 PM ET (US)     Profile for grogden  Send Email to grogden     
thanks for the feedback.My tank is fiberglass and I think algae grew from the strong sunlight since the boat had been sittng with very little gas when I bought it.I changed the fuel line,which was 15 yrs old,put in omc 2+4,and I'll see if the sediment goes away, otherwise I'll have to pull the tank.
where2 posted 08-10-2001 12:30 PM ET (US)     Profile for where2  Send Email to where2     
SuburbanBoy, if you think the cobalt at 55mph was a rush, you should feel what the 15' Sport is like at 50mph. I'm stumped why your Tohatsu doesn't run over 40mph. If I run my 17" 3 blade aluminum on my '85 70Hp Johnson, I am turning more than redline at WOT. With the 19" 3 blade SS, it runs real close to redline, and with only one person in the boat will run 48-50mph with serious chine walking.
The difference between the Cobalt and the 15' Sport in feel has alot to do with your behind being 12" off the water in the 15' Sport. Kinda like a buick running 30mph and a go-cart running 30mph. Go-cart feels faster because you're 3" off the asphalt with the wind in your face and the engine screaming behind you. :)
Bigshot posted 08-10-2001 01:41 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
My GPS is set to MPH, my engine was a 1990 70hp Johnson PTNT with a suzuki 19" worked to about 21" SS prop. I had it mounted about 2"+ and it would not turn to save it's life and I only picked up 1/2 mph. Lowered it a notch and she was on. If I trimmed her up there was nothing in the water but a 2' patch in front of the engine, sides, everything was out of the water. Mine was the 15 center console which is a bit heavier than a sport. My 79 sport had a 84 60hp johnson 2cyl with a 19" ss prop mounted close to the transom and no PT. She would do low 40's but holeshot was a bit slower. Also had a 88 15' Supersport with a 50hp johnson and that did MAYBE 40. Had to sell that boat because that wood was just too much work. The center console was my favorite model, you can stand up for short distances. I was gonna do a 90hp Yamaha on my 15' CC but opted for the 70 due to liability, hindsight being 20/20, should have done it. Was in Barbados and the hotel had a 78 15' sport with a 115 Eveinrude Ocean pro...HOLY COW! that did over 50, not 1 stress crack either. Guy by me has a 13' supersport with a 3cyl 60hp Johnson, have not had the opportunity to talk to him yet. Sorry about rambling but nothing has more fun factor than a chine walking classic 15'.
ValkariaKid posted 08-10-2001 02:01 PM ET (US)     Profile for ValkariaKid  Send Email to ValkariaKid     
Pardon the dumb question, but what does PTNT mean?
I see it alot on this board referring to engines.

Is it Power Tilt N(and) Trim?

Just a guess..



Peter posted 08-10-2001 03:54 PM ET (US)     Profile for Peter  Send Email to Peter     
Had a friend with a 15 Sport and a tricked out 70 Evinrude turning one of those exhaust over hub, elephant ear stainless bass boat props. Initial hole shot was lousy because the engine wound up until the prop caught -- but man did you have to make sure you were holding on once it caught! It was a lot like dropping the clutch on a muscle car. No GPSes back then, but estimate of top speed was over 50 with enough chine walking for a life time. I don't think that the 15 is aerodynamically suited for a 115. ;)
SuburbanBoy posted 08-12-2001 01:09 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
I will jack up an additional 1" today. Ran the length of Lake Charlevoix wide open yesterday morning, and saw 37.5 mph on the way back. Had to tilt the motor so far forward that the leading edge of the cavatation plate was slightly digging in and spraying water up like a mini jet ski. I will report back with results later.


Pat Smith posted 08-12-2001 01:27 PM ET (US)     Profile for Pat Smith  Send Email to Pat Smith     
I've got a 18ft outrage 85' with an 150hp johnson 85' and the fastest that I could go is 37 mph,using my GPS.Is this average? or should I be able to go faster?Does the age of my motor have all to do with it?I'd just like to compare what you guys are getting?Thanks-Pat
Peter posted 08-12-2001 04:11 PM ET (US)     Profile for Peter  Send Email to Peter     

37mph is too low unless you're running into a 5 to 7 mph current. I used to get mid to high forties with my 1987 18 Outrage/150 Johnson. Motor was mounted one notch up and was turning a 21" OMC Raker, WOT of 5000 RPM. Your WOT should be between 5000 and 5500, depending on the pitch of the prop its turning? 17 to 21" is the typical range with 17 to 19" being the most typical. If your prop is in the 17 to 19" range and your WOT RPM is below 5000, then your motor has some issues.

Bigshot posted 08-13-2001 12:51 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
PTNT=Power tilt and trim. 37 too slow for that 18' Heard they do close to 50.
ValkariaKid posted 08-13-2001 05:40 PM ET (US)     Profile for ValkariaKid  Send Email to ValkariaKid     
Thank You Bigshot-

I'm new to boating, and wasn't too sure what it meant.
I figured that someone would answer eventually!


Flipper posted 08-23-2001 11:06 PM ET (US)     Profile for Flipper  Send Email to Flipper     
I've always fantacized about having a
90 hp. on our 15' sport. I finally
broke down and got a 90 Merc in'99 and
it's been three years of tweaking, having
fun for a while, then tweaking again. The
boat did 49 (gps) with two people before I mounted the motor as high as she'd go (2" off) with a 26"p Laser2. With no GPS
this time, all I knew was I was now keeping
stride with many of my friends' faster I/Os,
even with two in the boat.
Last week, I installed a manual jackplate and
this really tamed the chine walking.I was able to raise the engine a total of 3" off
-before I would need to buy a surface prop,
low water pickup, etc.(I may get bored
again some day)
This is NOT an upwind machine. Very stable,
though. Ill let you know the speed when my
brother brings his GPS to the cottage!
lhg posted 08-24-2001 12:24 AM ET (US)     Profile for lhg    
Flipper - that could be a good handle for a guy with a jacked up Merc 90 on a 15 sport!!!
Take it easy out there.
bdb posted 08-24-2001 08:30 AM ET (US)     Profile for bdb  Send Email to bdb     
Welcome aboard Flipper! Ya gotta love that kind of experimentation!

Just 2 questions:

1. When was the last time your well-water was checked?

2. Where, exactly, to you boat?

Harpoon Harry, puttin' a 5 horse Elgin on the Montauk

SuburbanBoy posted 08-24-2001 01:49 PM ET (US)     Profile for SuburbanBoy  Send Email to SuburbanBoy     
Based on my personal experience, I wish I had purchased a 90hp for my 15', instead of my 70hp. I guess I still miss the kick of my old Mercury Black Max 200. But, I am within the name plate rating.

When you say 3" off, what do you mean?


Flipper posted 08-27-2001 12:15 AM ET (US)     Profile for Flipper  Send Email to Flipper     
By 3" off I meant the cavitation plate
is 3" above the bottom of the boat.
(after looking more closely this weekend
I think it may be 4")
I had an awesome weekend - I invited the
boss to the cottage and took he and his
wife on a high speed tour, the three of
us on one mahogany plank (his wife sat
in the middle) screaming along...he waited
until the end of the trip to tell me he
was having prostate troubles!
Cliff posted 08-29-2001 10:37 AM ET (US)     Profile for Cliff  Send Email to Cliff     
For what its worth....

For the last 2 summers I could not figure out why my 1987 15 with a 99 50 Yami was only running 4500 rpm....

Tried everything.....a different prop, trim angles etc. Still notta

Gave in last week and took it to the Yami dealer who cleaned the carbs(a little dirty) and ran it...still no improvement.....

For 2 days the machanic tinkered...until he looked at the throttle cable mechanism where it meets the was installed upside down.

As a result of this snafu either in the factory during assembly or when it was rigged on the boat...the boat was running with carbs only halfway open(about 28 mph WOT)

Now it does 38 mph with a full tank and one person.....

I'm just glad that I found the problem now rather than in another 2 summers.

Its always the most obvious things.


Flipper posted 08-29-2001 10:03 PM ET (US)     Profile for Flipper  Send Email to Flipper     
Harpoon Harry, I stopped drinking the
river water a while ago, but there may
be permanent damage.I'm on the St. Lawrence.

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