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#4808919 - 07/09/18 08:57 AM Portable outboard power question
thunderfog Offline


Registered: 03/12/14
Posts: 451
Loc: Eleanor, West Virginia
Hey everyone, I'm trying to max out power for a Zodiac inflatable boat. So, considering [/i]only[i] these two factors, which engine is a better option strictly from a power i.e. potential top speed standpoint:

A new 4 stroke 9.9hp, or a 2 stroke 15hp with about 85-90% of the original compression?

Again, for this question, ignore other factors like year and brand of the 2 stroke, price etc.

Interested to hear thoughts on this. Thanks!
_________________________
'16 4 Runner Kendall GT-1 FS 0w-20
'14 CX-5 GT AWD - QSUD 0w-20
'78 Evinrude 15HP - E/J TC-W3
Honda GCV160 - Pennzoil Ultra 10w-30

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#4808924 - 07/09/18 09:04 AM Re: Portable outboard power question [Re: thunderfog]
Phishin Offline


Registered: 05/01/12
Posts: 2459
Loc: Indiana
I kid you not, but my dad had a 47' Chris Craft with an inflatable dingy on it. One day we got it off the boat and fired it up.

To our surprise, the little soft bottom inflatable had a 25HP 2-stroke Johnson on it!!! Holy COW was that thing fast and fun!!!
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#4808934 - 07/09/18 09:17 AM Re: Portable outboard power question [Re: thunderfog]
CT8 Offline


Registered: 10/09/14
Posts: 11230
Loc: Idaho
Why the apples and oranges comparison?
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#4808945 - 07/09/18 09:32 AM Re: Portable outboard power question [Re: thunderfog]
UncleDave Offline


Registered: 06/02/14
Posts: 1708
Loc: Ca.
85% of 15 is bigger than 9.9 plus the 2 stroke weighs less.

UD
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#4808976 - 07/09/18 10:00 AM Re: Portable outboard power question [Re: thunderfog]
billt460 Offline


Registered: 03/30/15
Posts: 4554
Loc: Glendale, Arizona
This brings up something I've always wondered about. How the Navy SEALS launch their inflatable boats from submarines underwater. Inflate them, and keep the outboard motors attached to them from becoming waterlogged?

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#4808978 - 07/09/18 10:01 AM Re: Portable outboard power question [Re: CT8]
thunderfog Offline


Registered: 03/12/14
Posts: 451
Loc: Eleanor, West Virginia
Originally Posted By: CT8
Why the apples and oranges comparison?


Ok, you asked for it. Here's the long version.

I have a '78 Evinrude 15hp, the one in my sig. Rolled the dice on it a few years ago, and it's probably toast at this point...been chasing problems and has left me SOL on Lake Erie too many times at this point. My marine mechanic also agrees it's time to move on.

The older two stroke outboards...the 8, 9.9, and 15hp blocks were all the same in many cases, and the same weight...about 80lbs. This weight is pretty much the max for me as far as pulling the outboard off and on the transom on a regular basis like I have to do.

So I'm looking at replacement. There are a small handful of older outboard options. 2 that I looked at (15hp) and did compression checks on were about 85%. So was the one I'm bailing on.

In the newer 4 strokes, the 9.9hp is a smaller engine than the 15hp, and they weigh about 81lbs and 97lbs respectively. The 15hp 4 stroke is out in this case. Why a new 4 stroke? The weights have come down in the last few years, and every lb counts.

When I take my wife and daughter out, the 15hp 2 stroke gets the boat on the plane. My brother's 2 stroke 9.9 struggles. So when finding a replacement, I'm right at the cusp in terms of power, so I don't want to lose any. I just can't do the 4 stroke 15hp, so I would have to do the 9.9hp 4 stroke if I go that route. And a 15hp 2 stroke if I go down that road again.

And then of course there are cost considerations. Used would be about a third of a new 4 stroke. Maybe I get a good one. Maybe I get someone's problems. Marine repair costs add up fast.

The ultimate question, which I tried to word in the OP, is will a new 9.9hp 4 stroke match the output of an older 2 stroke 15hp with what seems to be a normal decrease in compression from age/use?
_________________________
'16 4 Runner Kendall GT-1 FS 0w-20
'14 CX-5 GT AWD - QSUD 0w-20
'78 Evinrude 15HP - E/J TC-W3
Honda GCV160 - Pennzoil Ultra 10w-30

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#4808991 - 07/09/18 10:13 AM Re: Portable outboard power question [Re: thunderfog]
WobblyElvis Offline


Registered: 09/23/14
Posts: 1386
Loc: Toronto Canada
If the 15 hp 2 stroke runs well, it will trounce the 9.9.
Will it last if compression is down?
Can the engine be brought back to life with a ring job cheaply?

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#4809010 - 07/09/18 10:28 AM Re: Portable outboard power question [Re: thunderfog]
maxdustington Offline


Registered: 01/21/17
Posts: 886
Loc: Toronna
Originally Posted By: thunderfog
I have a '78 Evinrude 15hp, the one in my sig. Rolled the dice on it a few years ago, and it's probably toast at this point...been chasing problems and has left me SOL on Lake Erie too many times at this point. My marine mechanic also agrees it's time to move on.

Sounds to me like you need to find a new mechanic, or at least a second opinion. Of course he would want you to replace a motor that has stumped him, eventually you are going to take it somewhere else.

EDIT: Everyone is going to tell you to keep the 2T because any gearhead loves a 2T because it is lighter, more powerful and easier to fix. It seems that you need the 15hp without the 4T weight penalty, so you need a 2T 15hp outboard. You could just buy a newer used one, but I am afraid it would be a lateral move unless you pay a premium for a low hour dreamboat in mint condition. You could probably find a nice one in the offseason if you can limp it through, just wait for a really nice one to come up for a good price around Christmas.

I'd fix what I had but if you have been stranded by it multiple times, I would consider purchasing a nice one especially if you have more money than time. I actually drove a water taxi that had a newer Yamaha 15hp 4T tiller for a summer and it was very smooth and reliable, that was nine years ago and the motor was probably early 2000s.



Edited by maxdustington (07/09/18 10:41 AM)
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#4809015 - 07/09/18 10:31 AM Re: Portable outboard power question [Re: thunderfog]
RTexasF Offline


Registered: 10/01/02
Posts: 2901
Loc: North TX
It depends how old the 15HP two stroke is. Old ones were measured at the crank where the new 9.9 four stroke will be measured at the prop. If it's in good running order I'd prefer the 15.

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#4809040 - 07/09/18 10:54 AM Re: Portable outboard power question [Re: maxdustington]
thunderfog Offline


Registered: 03/12/14
Posts: 451
Loc: Eleanor, West Virginia
Originally Posted By: maxdustington
Originally Posted By: thunderfog
I have a '78 Evinrude 15hp, the one in my sig. Rolled the dice on it a few years ago, and it's probably toast at this point...been chasing problems and has left me SOL on Lake Erie too many times at this point. My marine mechanic also agrees it's time to move on.

Sounds to me like you need to find a new mechanic, or at least a second opinion. Of course he would want you to replace a motor that has stumped him, eventually you are going to take it somewhere else.

EDIT: Everyone is going to tell you to keep the 2T because any gearhead loves a 2T because it is lighter, more powerful and easier to fix. It seems that you need the 15hp without the 4T weight penalty, so you need a 2T 15hp outboard. You could just buy a newer used one, but I am afraid it would be a lateral move unless you pay a premium for a low hour dreamboat in mint condition. You could probably find a nice one in the offseason if you can limp it through, just wait for a really nice one to come up for a good price around Christmas.

I'd fix what I had but if you have been stranded by it multiple times, I would consider purchasing a nice one especially if you have more money than time. I actually drove a water taxi that had a newer Yamaha 15hp 4T tiller for a summer and it was very smooth and reliable, that was nine years ago and the motor was probably early 2000s.



Part of the consideration also... the unreliability of my current engine does not mix well with taking out my 3 yr old girl who *loves* the boat... and that is half the fun of the whole venture. I gotta think of her safety. A 30 min ride on Lake Erie in summer heat that could turn into 2 hours rowing in or even waiting for a tow...

I'm trying to avoid paralysis by analysis, but there are a lot of variables here.
_________________________
'16 4 Runner Kendall GT-1 FS 0w-20
'14 CX-5 GT AWD - QSUD 0w-20
'78 Evinrude 15HP - E/J TC-W3
Honda GCV160 - Pennzoil Ultra 10w-30

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#4809114 - 07/09/18 11:47 AM Re: Portable outboard power question [Re: thunderfog]
maxdustington Offline


Registered: 01/21/17
Posts: 886
Loc: Toronna
Originally Posted By: thunderfog
Originally Posted By: maxdustington
Originally Posted By: thunderfog
I have a '78 Evinrude 15hp, the one in my sig. Rolled the dice on it a few years ago, and it's probably toast at this point...been chasing problems and has left me SOL on Lake Erie too many times at this point. My marine mechanic also agrees it's time to move on.

Sounds to me like you need to find a new mechanic, or at least a second opinion. Of course he would want you to replace a motor that has stumped him, eventually you are going to take it somewhere else.

EDIT: Everyone is going to tell you to keep the 2T because any gearhead loves a 2T because it is lighter, more powerful and easier to fix. It seems that you need the 15hp without the 4T weight penalty, so you need a 2T 15hp outboard. You could just buy a newer used one, but I am afraid it would be a lateral move unless you pay a premium for a low hour dreamboat in mint condition. You could probably find a nice one in the offseason if you can limp it through, just wait for a really nice one to come up for a good price around Christmas.

I'd fix what I had but if you have been stranded by it multiple times, I would consider purchasing a nice one especially if you have more money than time. I actually drove a water taxi that had a newer Yamaha 15hp 4T tiller for a summer and it was very smooth and reliable, that was nine years ago and the motor was probably early 2000s.



Part of the consideration also... the unreliability of my current engine does not mix well with taking out my 3 yr old girl who *loves* the boat... and that is half the fun of the whole venture. I gotta think of her safety. A 30 min ride on Lake Erie in summer heat that could turn into 2 hours rowing in or even waiting for a tow...

I'm trying to avoid paralysis by analysis, but there are a lot of variables here.


Here, in Toronto I was looking at outboards recently, and it seems like a used good condition modern 4T 9.9 is worth about $2000-2500 for a 9.9 where an old 2T 9.9-15 would be around $800 maybe $1500 for a good condition newer 15hp. I was looking last week, so those are recent peak season prices.

I think a newer one is better bet because they will hold their value better. I think a lot of people are in the same boat as you, as the old ones are all worn out by now. Why bother screwing with the carb on a 2T every season when you can get a 4T with fuel injection and a check engine light for an extra $1000.
_________________________
03 Jetta AWP/09A 200k kms
Edge 0W40 + Mann 719/30

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#4809885 - 07/10/18 07:04 AM Re: Portable outboard power question [Re: thunderfog]
JTK Offline


Registered: 08/14/03
Posts: 10655
Loc: Buffalo, NY
I've used 2 and 4 strokes in this power range. Like said, even with some age, hours and wear on it, that 15hp 2-stroke should outpower the 9.9 4 stroke. A mint condition, super running/performing 15hp 2cycle should smoke the 9.9 four. Literally! lol.
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2017 Ram 1500 4x4, 3.6L. 2016 Nissan Quest SV (Babe magnet IV)

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#4810530 - 07/10/18 05:14 PM Re: Portable outboard power question [Re: thunderfog]
Warlord Offline


Registered: 10/15/06
Posts: 996
Loc: Southwestern Alberta
More power is always good when it comes to boats. I find modern 9.9 4 strokes to be pretty sluggish compared to say an 80ís Evinrude 9.9 2 stroke. Also those old twins are dead reliable.
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