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Posts: 532
| I keep batting around the idea of repowering my 681C with a 115 (its max HP). Currently is has a 70 Johnson that is adequate, hole shot isn't what I hope for but does well enough for that size motor, top speed is good all things considered.
Repowering my boat really got stuck in my brain a few months back when my partner and I fished Cave Run PMTT out of my boat. One of the judge boats was a 680 with a 115 Yamaha. So I struck up a conversation in the parking lot about how the boat went with the 115... The top speed he told me was impressive, like take it with a grain of salt kind of number.
So I do not want to just blurt out what this fella told me because it is almost unrealistic. But anyone with experience with this hull and a motor in the ball park of 115 please chime in with top speed numbers, and opinions on hole shot, and what prop your running.
I got a few very nice 115s I am looking at, but just teetering with I got a perfect running motor that's adequate on one hand VS. spending money on a motor I do not absolutely need, but would be really fun and would put my mind at ease.
Any opinions?
Edited by anzomcik 6/27/2013 8:30 PM
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Posts: 113
Location: Northwest Wisconsin | i have a 2005 honda 4stroke on my 92 681. Not sure what the prop is but i can get 38-40 on my gps. Running 4k on the tach. |
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Posts: 3514
Location: Elk River, Minnesota | If you are running 4K on your tach, you are way way way below max RPM for that motor.
With a change out to a 115, I would suspect on that boat you would see 42 - 45 or so propped correctly.
Steve |
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Posts: 152
| Just bought a 92 681C this spring. It has a 2003 115 yamaha 2 stroke. Hole shot is great, tops out at 42 with 2 guys and gear. |
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Posts: 59
| I have a 93 681C with a 93 115 yamaha. My boat will do 45-48 with two guys and gear per gps. I can get 49-50 out of it by myself with 1/2 tank of fuel. Of course all of these speeds are based upon conditions and wind etc... |
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Posts: 1150
Location: Minnesota. | I had a '97 681VS w/a 115HP 2 stroke Yam on the back since new. It was a perfect match for the boat!
Too bad she went up in a garage fire last yr.
Ranger Z118, 150 4 stroke Yam now. Pretty happy but there was nothing wrong with that 681!
I'd do it.
EDIT: Forgot, I could tag approx. 46-47 mph on my 681, this is per the onboard Yam. speedometer only. Never checked it any other way. And yes, the boat was rated for 130hp tops. I can't recall if I had a 17 or a 19 pitch prop.
Edited by Jeremy 6/28/2013 1:33 PM
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Posts: 532
| Ok now that I have a base line of what different owners get speed wise, I know that fella was padding the numbers. He told me he would get 62-65mph.
Becuase I am getting 33-35mph with my 70hp, I think it would be silly to repower if I would get 40-42 mph, but a few of you said 45mph or more thats a nice gain if that is feasable. |
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Posts: 2088
| You put a new 115 ProXS on there and prop it for top end .. I'm sure you could get 50mph +....but to me top end speed is overrated - hole shot and handling are more important. |
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Location: Contrarian Island | it's not overrated w/ a big lightning storm bearing down on you ! 
115 2 stroke will for sure get 45 propped right, they are rated for 135hp as well and couple options in that size
Edited by BNelson 6/28/2013 1:17 PM
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Posts: 59
| I think pre 95 they are only rated for a 115 since they are actually 8" shorter than the updated VS model. |
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Location: Contrarian Island | ah yah, the older ones were 115 |
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Posts: 2088
| BNelson - 6/28/2013 1:15 PM
it's not overrated w/ a big lightning storm bearing down on you !
115 2 stroke will for sure get 45 propped right, they are rated for 135hp as well and couple options in that size
Brad -I agree, you don't want to not look at top end at all ..but your scenario is a perfect example, a storm is blowing in its most likely going to be rough conditions, I want a prop to jump on plane and will bite in rough water - you wont likely be getting your "perfect" top end speed in these conditions anyway, don't ignore top end but prop this boat to do 50mph in great conditions will probably cause it to not get on plane well vs. 45 mph but jumps on plane with two guys, is what I meant, Ive been messing with props lately and I'm just saying top end isn't everything  |
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Posts: 5874
| VMS - 6/27/2013 11:25 PM
If you are running 4K on your tach, you are way way way below max RPM for that motor.
With a change out to a 115, I would suspect on that boat you would see 42 - 45 or so propped correctly.
Steve
Also if only 4K at WOT, you are lugging your motor, and that is not good for it. You should be propped for the MAX RPM range at WOT.
Edited by Shep 7/1/2013 3:59 PM
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Posts: 103
| I just put a new Merc 115 4 stroke on my '97 681vs. Top speed with a 13x19 3 blade prop and just me in the boat is 47. Hole shot lightly loaded is fine, really loaded down "smoke 'em if you got 'em". MPG much better than my old motor.
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Posts: 5874
| What's your tach reading at WOT? Lightly loaded you should be at the upper end of the Max RPM range, if not ticking the limiter. If hole shot is suffering when loaded, go down to a 17P and try it. You probably won't lose top end speed. Is your prop SS?
I'm sure VMS will weigh in on this, and he's pretty good with prop issues.
hehehe "Smoke 'em if you got 'em" That's what got me started in boot camp! If you didn't, you had to be in the barracks. Smoke 'em, and you could be outside.
Best thing I ever did was quit 8 1/2 years ago.
Edited by Shep 7/3/2013 8:17 AM
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Posts: 532
| Update.
I bolted on a nice used 115 fast strike on sunday. Took it out for a couple test runs
Impressions: holeshot better than my 70, not out of this world but not bad. would like to see it improved
Handling was pretty good, no venting in hard corners. not the best handling prop but above average
Plane speed was in the 18mph range.
42.5mph GPS
5050-5100 rpm WOT
alum 14" dia 19" pitch (looks like stock OMC)
with 2:1 ratio LU it puts me at 9.3% slip
WOT range 4500-5500
What would you do? 17 pitch SS or 17 pitch 4 blade Al
Any brands props you would recomend?
Edited by anzomcik 7/9/2013 12:12 PM
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Posts: 532
| I just answerd my own question. It just crossed my mind to check to see if my 70s prop would fit my 115. What do you know it did.
13.375 dia 17p SS
Hole shot very good, handling better than the old 19p
5600rpm 10 gallons of gas in a 23 gal tank, one person (normal load it two guy and partners gear)
42.5mph GPS
My slip stays about the same, so I am very pleased.
I am a little high on the rpms but I am also lighter than normal, picked up better hole shot and handling. I didn't gain speed but I got the next best thing, NOT losing any speed but gaining in two other categories. |
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Posts: 5874
| I think you got it right. Your RPM's will go down when you fill it up, and add your partner(s). |
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