What size motor?

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FormerParatrooper

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May be a dumb question, but I am trying to decide what motor size to get. I currently have a 9.5 hp Johnson, runs well but slow on the river. My boat is a 14ft Semi V, weighs about 175lbs. Max rating is 25 hp. With everything on a typical trip, I figure about 500 lbs of added weight (me, dog, gear, fuel, battery, motor etc).

The river current is slow generally, it is the Illinois River in Peoria area. I am thinking to get a few places I want to go in a reasonable time, need to move about 25 knots or so. The 9.5 is pushing about 14 knots per GPS going up river. Where I fish off river and in lakes, max Hp is 25, so that is not a concern.

Would a 15 Hp have the power if set up appropriately? My 9.5 weighs about 60 lbs, so wondering about the extra weight of a newer motor as well, since boat is a 1979.
 
It's usually recommended to get something near the max if you can afford it, even if you have to reinforce the transom (keep in mind, 1979 was 2-strokes - today's 4-strokes weight maybe 30% more)

Would a 15 be better than a 9.5?
Sure. Could you expect a linear, 66% increase in speed (1.663 x current speed)?
Unlikely.
But it's probably gonna be about half again as much.

[emoji12]
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You're always gonna wish for something bigger.
Initially, you'll be impressed with the 15's boost. But, in time you'll "feel" the boat could absorb more.

How far can you go down this line?

Keep in mind that your older boats original max of a 2-stroke, 25 HP engine was for a power plant that was generally lighter, and which developed power through RPM and not booming torque.
One of the reasons 4-strokes are heavier is to absorb the forces involved with all the extra machinery and torque that is part of their makeup.

It might be more relevant at this point to know how much motor weight your boats transom was designed for.
My bet is you're gonna exceed that by the time you reach 20 HP in a 4-stroke HP

PS will you be through-bolting the increased power plant to the transom?

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DaleH said:
I'd look for an e-start 2-stroke 25hp ... and wouldn't look back ...
Yes the MODERN 2 STROKE 25hp is very different than those from 1979
A new 25 hp Evinrude 2S, for example has -

Precision Oil injection lubrication- no more mixing gas and oil.
They also employ scavenged lubricant recirculation - no more unused/unburned oil out the exhaust.

E-TEC:
Direct Fuel Injection
Electronic engine control

From what little I know about engines, this is the peak of 2-stroke evolution. These things were only a dream 15 years ago, and they finally realize the promise of the 2-stroke engine.
This means fast throttle response, zippy performance, and clean emissions the equal of 4-strokes.
They also are in your price range (barely), and weigh less.

Check this:
https://www.evinrude.com/en-us/engines/etec_inlines/etec_25_inline
 
You can usually get motors 20HP and under without going through a dealer install etc. TBH, my thoughts are that a 20HP should probably get you pretty close, and are often the best on weight vs power. I get 23MPH with a much heavier 1552 boat, but that's the top end with the prop that I have installed. I know in the case of my Tohatsu, the same block is used for the 15-20HP, the motor is just restricted on the lower HP model. Once you go to the 25, yeah you get more HP, but the motor weight also goes up considerably. Every OEM is going to be a bit different in that regard, but that's how to Tohatsu models are, and they also build the units for Mercs as well.

If you go 20 or lower, I haven't found anyone better on pricing(they price match too) than OnlineOutboards.com. They carry pretty much all the models for 20HP and below, no tax if you are not in their state, and shipping is free. Bought my '15 Tohatsu 20HP from them and have only great things to say about them.
 
I would recommend a 25 if your boat will handle it. I bought a slightly used motor (after giving it a full checkup and running it on the water) for way less than your talking about. I avoid the brand new 2 strokes because of the oil injection system failures. If you go new. go 4 stroke. if you go used, I personally would bypass any injections system and mix it yourself. Hard to screw that up.
 
It's probably worth mentioning that in most MODERN 2-strokes, you're not burning oil in the combustion chamber any more.
In the Evinrude system, for example, oil and gas never see each other.
The oil is now used for direct lubrication, and is scavenged and recirculated. This is the primary reason they can exceed both US and foreign emissions standards.

The troubling oil/fuel injection systems of a couple decades ago are gone.

Plus 300 hour maintenance cycles... dang!

Here's something to wet your whistle on the subject:

https://www.allatsea.net/outboard-engine-roundup-examining-todays-two-stroke-engines/#comment-97105

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Lot of good comments, that's why I like this site.

I was considering something new, ease of maintenance, but I am a bit old school and the 2 stroke sounds are pleasant to my ears.
The thought of thru bolting my transom is probably not something I am willing to do. That will leave me with going to an older motor in 20 or 25 hp. I am a Johnson fan, my Grandfather ran Johnson's and my best memories are built around them.

As far as reputation, which years of the Johnson 20-25 hp have the best record of reliability?
 
FormerParatrooper said:
Lot of good comments, that's why I like this site.

I was considering something new, ease of maintenance, but I am a bit old school and the 2 stroke sounds are pleasant to my ears.
The thought of thru bolting my transom is probably not something I am willing to do. That will leave me with going to an older motor in 20 or 25 hp. I am a Johnson fan, my Grandfather ran Johnson's and my best memories are built around them.

As far as reputation, which years of the Johnson 20-25 hp have the best record of reliability?
You got me there. I wouldn't have a clue

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Vote for a 25hp....

I have a war eagle 1548. Heavy boat. Ran a 15hp on it a while and liked it. I originally had a 25 on it, and put the 15 on it for giggles. It ran 23 mph with the 15hp and the 25 runs in the 29mph range with just me, when my girlfriend goes with me, right in the 26-27mph range full bore. With the 15, it would barely plane us, just me it was "ok" but sluggish.

Remember the torque difference. The 25hp has a LOT more torque than the 15 does, which is especially useful if you want to get out of the hole with a load in the boat, like, say you're trying to outrun a barge or something along those lines.

In this area the 25hp is "king". Not because the local duck hunting areas are 25hp limited, but because the 25hp motor is so versatile. For $3500, you should almost be able to pick up a new one if you shop around. I have seen the Yamaha's at the dealers for just a shade over $3500, brand new-electric start too.
 

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