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  15' Sport: 50hp or 70hp?

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Author Topic:   15' Sport: 50hp or 70hp?
KeysNole posted 04-14-2002 02:42 AM ET (US)   Profile for KeysNole   Send Email to KeysNole  
I am looking to restore a 15' sport, and have the option of picking up a 50hp Yamaha or 70 Suzuki. The price difference is about 1K cheaper on the Yamaha. What are my performance differences, besides the obvious? Any speed calculations would be appreciated.
PMUCCIOLO posted 04-14-2002 06:02 AM ET (US)     Profile for PMUCCIOLO    

Are the engines two stroke or four stroke? What is the weight difference between the two? What is your intended use for the boat? What are the differences in the warranties between the two?


Ron Brassord posted 04-14-2002 09:43 AM ET (US)     Profile for Ron Brassord  Send Email to Ron Brassord     
I am getting experiance on my newly acquired 85 15 Whaler with a mid 90's 70 hp Johnson, and find it will readily top 40mph and cruise smoothly at 25 with a moderate load. The mpg is about 5 with mixed speeds, and a 6 gallon tank will last about two hours. I had thought the 70 was too much, but the boat does just great in all conditions. If I had to make a replacement I would go for another 70.
Hope this helps Ron B
mudpuppy posted 04-14-2002 10:12 AM ET (US)     Profile for mudpuppy  Send Email to mudpuppy     
On my 87 Supersport limited powered by a 60 hp merc 2 stroke, I can top end at about 34 with a moderate load (1 passenger, 2 batteries, a few gallons of fuel, no kicker, no dog). Cruises great at about 23-25 (GPS as speedo). I wouldn't want a 50 but if you're not in too much of a hurry it'd be okay. Agree, consider the weight difference between the two engines.
bc posted 04-14-2002 05:05 PM ET (US)     Profile for bc    
I have the same setup as Ron, and observed about the same performance. I would go with a 70 2-stroke also.


Alan Hiccock posted 04-14-2002 05:13 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
I just got home from a day on the water with my 15 sport/70 yamaha setup.
This boat loves 70 hp. It really gets out of the water and hits 45+ with a full load including my fat arse , gas & gear.
But one thing dawned on me today. There was a post where a gent was inquiring weather he should rig his 15 sport with a 70 or a 50 & mentioned he has young sons who'll be using the boat, in his case I'd say get the 50. It hit me today when some weather came in & I was following a big Bertram up the channel in confused seas, YOU CAN REALLY GET IN TROUBLE WITH THIS BOAT WITH A 70. You have to have discipline, its a lot of speed to be on a wooden bench, with no windshield bent down . But it's the right motor for the boat, less load, extra HP to get you home & the hull is designed like a speedboat almost.
just be carefull. Alan
jameso posted 04-14-2002 08:16 PM ET (US)     Profile for jameso  Send Email to jameso     
OK, I will buck the trend,,I have a 15 sport with mid 80's OMC two cyl,two stroke. My top end VIA GPS is 36/38. The hole shot will scare you!! (2 cyl=torque). My engine weighs
183. Yeah would like some extra horses to play with the bass boats,,,but my 03 would rather have a strong 50 or 60 with T&T as a 70/75 without.
And like Alan says it is real easy to get too much in this rig. Speed is only good on cal waters that you know. I would expect that most 70's will not be doing near the max speed in rough stuff.
A note, the 15 is just on plane at 20+, don't care what is on the back, Hull planes at 22/23 or more according to load.
Jim Armstrong
jimithing posted 04-14-2002 09:10 PM ET (US)     Profile for jimithing  Send Email to jimithing     
Maybe its just me but a 70 on my 15 would scare hell outta me....I am no small potato at 220 lbs and my yam 50 does just fine with 2 6 gallon tanks my wife and a battery.....have almost gotten myself into trouble a couple of times with this are right it is a speedboat hull and once on plane it doesnt need much to make her run...the 50 is the right choice....
Alan Hiccock posted 04-14-2002 10:10 PM ET (US)     Profile for Alan Hiccock  Send Email to Alan Hiccock     
It is scary Jimithing, today for the first time scared myself a little going over awake @ around 40.
As a kid had a 16 Checkmate with a 115 Merc.
The thing was it had wrap aroung bucket seats & the steering wheel facing you from the dash helps too I think.
The Whaler with its bench seat makes it scary when you run into some snotty stuff @ 45 mph's . If you stuff the bow theres nothing to brace you too. Its not a smart choice rigging a 15 w/a 70 for a teen I dont think, Alan
Bigshot posted 04-15-2002 10:58 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Being he mentioned a 70 Zuki, I assume he means 4 strokes being Zuki does not make 2 stroke 70's. I would love to drive a 15 with a 70 Zuki but I know 340lbs is a too extreme for that hull. Go with a lighter engine...maybe look at Honda or Zuki 50's.
prj posted 04-15-2002 12:59 PM ET (US)     Profile for prj  Send Email to prj     
i agree with many posters herein. i have an '87 striper (15') with a '90 johnny 70 hp vro. top speed around 43 with me, batts, fuel, all gear.

on stripers, theres not even a bench seat, just a cooler, set high up i might add. that plexiglas is a windscreen? heheh, shields my lake maps and legs, no more.

super scary hole shot due, jumps right out on that hull design. travels comfortably in the 25-35 mph range. windy and volatile up near wot. watch that water in front of you!

jellisfeingold posted 04-16-2002 10:51 AM ET (US)     Profile for jellisfeingold  Send Email to jellisfeingold     
Until last summer I had a 70hp Johnson on a 15' GLS. Fast it was, but it was also unstable in anything but glass, and the exposure and speed scared the daylights out of the kids and most grownups. Since I live on choppy salt water I found myself poking around at 1/2 or 3/4th throttle. If these are things you want, go for it. I suspect it would be a nice ski boat combo - it took off and planed in about a nanosecond. If I were doing it again, though, I'd put my 50hp Honda 4-stroke on the 15', and the 70hp on my current 17' Montauk (which has the 50hp Honda). The Montauk could use the extra grunt of the 70.
flaglerdave posted 04-19-2002 11:52 AM ET (US)     Profile for flaglerdave  Send Email to flaglerdave     
I have a 15 Sport for years and have to vote for the 70. It handles like a champ and I cruise all day on a 13 gallon Tempo tank. I have a center OEM console with a flip back cooler seat and the tank is mounted in the front of console inside a customer seat storage.
Runs pretty shallow and planes quickly !
lhg posted 04-19-2002 02:20 PM ET (US)     Profile for lhg    
Some of us here would guess that a lightweight Merc 60 EFI four stroke would be the ultimate engine for a 15, and a perfect compromise for your problem. You might price one of those up from Sundance Marine or Bass Pro in Ft Lauderdale. You'll get the light weight of the Yamaha 50 and the 4 stroke EFI of the Suzuki 70.

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