60 or 90?

creativers

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Joined
Jan 30, 2010
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6
I recently bought an old 16? low-profile fiberglass ski boat. As a teenager I used to like to ski behind small light-weight boats, with almost no wake, so I?m seeking to recreate that experience.

This boat came with the original 115hp Merc, which according to my research weighs around 280#. I sold that motor, so I can repower with a new ETEC. My plan is to put a 90hp ETEC, which weighs 320#. That?s 40# heavier than the Merc. I have installed a gas tank in the bow, which should at least shift some weight forward. But I?m really contemplating getting the 60hp ETEC, which only weighs 240#.

The primary goal of this boat is to lift me out of the water on a slalom. I still only weight 165#. And there should be no more than 300 to 500# of people in the boat.

I?m not really concerned about being the fastest boat on the lake (even though the boat cries out to go fast). I?ve been told that the primary lake we will be on has now imposed a 40mph speed limit. And I could prop down the 60hp, giving up some speed to get more torque.

So my question is, do any of you have actual experience with such a small boat and motor, pulling a slalom skier? Would I regret getting the 60hp ETEC?
 

GeneH

Petty Officer 2nd Class
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Sep 1, 2007
Messages
109
Re: 60 or 90?

I've boated and skied for 50 years though not slalom. You didn't mention the weight of your boat. I've been a Starcraft aluminum fan for years and have a 60 Johnson on a 16 foot. I would think a 60 on a glass boat for slalom would be pretty marginal for power due to boat weight. If you want to get up on two and kick one off, it ought to do that.
 

kenmyfam

Supreme Mariner
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Aug 10, 2006
Messages
14,385
Re: 60 or 90?

Personally I would go with the 90hp. You should be at no less than 70% of the max HP for your hull for decent performance. Maybe a little more for skiing You may be very disappointed with a 60hp and then it's too late.
 

toeskis

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Jun 17, 2009
Messages
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Re: 60 or 90?

Personally, the old adage "there's no replacement for displacement" would apply in my opinion. I've skied on everything from 40 hp to 300, and the only problem with low horsepower is getting dragged. If you go with the 90, it will at least have the pop to get you out, and get the bow down at the same time. Getting dragged is a pain in the back, and will shorten your ski day pretty well.
 

el toro

Petty Officer 3rd Class
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Mar 2, 2008
Messages
77
Re: 60 or 90?

Those old Merc 115's are tough to beat in the horsepower vs. weight category, I think it would have been an ideal match on that boat. However between the two you've suggested I would pick the 90.
 

skibrain

Senior Chief Petty Officer
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Jun 17, 2004
Messages
766
Re: 60 or 90?

Post up some more info about the 16' hull you've got.
Weight, max rated hp, make and model. There are some good forums out there regarding some of the classic boats with tips on repowering.

My .02 is that 60 hp would be marginal. Yes could do it with the right prop and I've skied alot behind 40, 50 and 70 hp. I've owned 80's era 15.5' Glastron with a 90 Johnson, and a 16.5' Glastron with a 120 Evinrude.
 

superwooter

Petty Officer 2nd Class
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Oct 12, 2009
Messages
167
Re: 60 or 90?

.... and how about maybe a pic or two of your rig. pics are always appreciated, especially if you are unsure of the weight of your hull.
 

79Merc80

Senior Chief Petty Officer
Joined
Nov 22, 2007
Messages
673
Re: 60 or 90?

Not sure if you are aware of this or not, but if your Boat (Especially the Merc 115 you sold) was from ~ 1980 - 1983 or older, then the 90 you are thinking of would be about the same power. Somewhere between 80 and 83 Mercury shifted the HP ratings from the crankshaft to the propshaft. I would defiantely go with the 90. No need to run the **** out of a 60 when the 90- and cruise along at the same speed. I think the 90 would last longer too since you wouldn't have to have it reved up as high as the 60 would need to be to get the same performance for pulling a skier.

Just my 2 cents.

Craig
 

haulnazz15

Captain
Joined
Mar 9, 2009
Messages
3,720
Re: 60 or 90?

I have done slolam skiing behind a 110 or 115 Merc (I can't rmember which) and it was a dog. This was behind a 17ft fiberglass bass boat which didn't weigh hardly anything. That being said, I have been behind a 17ft fiberglass bass boat with an 80's 90HP V4 Johnson, and that thing had more grunt than the 115 Merc. I would go with the 90 if you choose to change engines, but if there was any way to grab more HP I'd do it. Once you get on plane, the size of the wake will likely be almost identical between the different motor weights.
 

trendsetter240

Lieutenant
Joined
Jun 22, 2009
Messages
1,458
Re: 60 or 90?

Definitely go with the 90hp. Forget about the 40lb difference you will not even notice it.

With the correct prop that 90 will pop you right out of the water. Plus you wont get a face full of 2-stroke smoke with the ETEC like you would have with that old merc!
 

el toro

Petty Officer 3rd Class
Joined
Mar 2, 2008
Messages
77
Re: 60 or 90?

If that 90 Johnson out performed a 115 Merc then there was something wrong with the Merc. Normally those inline Merc's will out perform a Johnson of the same power.
 

Black as

Chief Petty Officer
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Feb 22, 2010
Messages
417
Re: 60 or 90?

If your a slalom skier I would go for a 90 :)

60 I think the motor will have to work overtime
 

haulnazz15

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Mar 9, 2009
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3,720
Re: 60 or 90?

If that 90 Johnson out performed a 115 Merc then there was something wrong with the Merc. Normally those inline Merc's will out perform a Johnson of the same power.

I would have thought so, but the Merc just simply sucked. I was not impressed with it, and you don't see too many of the Merc 115's anyway. Probably with good reason. I think the Merc 150 is where they got it right. Those v4 90 Johnsons may smoke a lot, but from the 3 boats I've been in with them, they are usually bulletproof and have plenty of low-end grunt.
 

Moody Blue

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Joined
May 24, 2004
Messages
3,136
Re: 60 or 90?

90hp would be the lowest I'd choose for slalom, especially if doing a water start. If you choose the 60hp you'll need to equip yourself with a snorkel to be able to breath as you are dragged thru the water :D

I've pulled up 220Ib experienced slalom skiers in a 16ft runabout with an 80hp and it was very marginal. Have also driven a 17ft j-craft with a 225hp that will POP multiple skiers right out of the water with NO hesitation.
 

creativers

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Jan 30, 2010
Messages
6
Re: 60 or 90?

Thanks to all for your thoughts. Sorry I haven't responded sooner. I've been so busy working on the boat, along with the rest of life. It sounds unanimous for the 90.

FYI: The power rating on the boat is for 125hp. I don't know what they based that on, weight or transom strength, but of course that's in old hp (at the flywheel) so the new 90 will be about 85 to 90% of that.

If you want to see the boat, ArchBuilder is restoring the exact same model. Note this is not me, just the exact same model. As you can see in his pictures, the side walls at the back are about 14", thus my concern with the heavy engine. Please continue reassure me that it will be safe.

Here's pictures of ArchBuilder's boat:
http://forums.iboats.com/showthread.php?t=364284&page=32
 

Kobie

Cadet
Joined
Jan 10, 2009
Messages
28
Re: 60 or 90?

If its rated for 125hp why not get etecs 115 HO. That is one sweet motor, and highly under rated, both figuritvely and physically. If you have the funds, why not get the 115, and in the future if you sell the boat, that motor is versitile enough to be used on other boats. A quick word about the 60 etec...Its a two cyclinder motor that can reach that hp by the water being pumped into the exhaust. Without that feature its basically just a little 40hp. So go for the 90 if you want, but I wouldnt over look the 115 HO.
 
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