Actual HP of Small outboards or Kickers

[Boatist]

I Thinking of Upgrading my 1975 15 HP Johnson to a Electric Start 15 to 20 HP 4 stoke motor.

I see lots of motors that share a power head but are rated at different HP.
My 1975 15hp and 9.9hp Johnson are an example. On these motors the difference is in the Carberator and the exhaust tunning. From what I have heard the low end HP is the same and the extra 5 hp only comes into effect at WOT and high end of the RPM range.

Also I know that the HP is not exactly 9.9 and 15.0 HP.

So here is my question:
Does anyone know of a sourse of actual HP rating for motors.
Like is a 15 hp actually 14.86 or 16.7?

Motors I an looking at are the Honda 15HP and 20HP and they share the same power head. The 15 HP has some options I am interested in like a 25 inch shaft but would like to get as much HP as possible with the same weight engine. I seen one report that the 15HP really produces 19HP.

Yahama 20 hp is another motor I am looking at.

If anyone knows of a site or that reports actual tested HP I would love to know it.

Would also like to here opinions or any facts people have about the
HONDA 15 HP and 20 HP and the Yahama 20 HP as kickers on a 21 foot boat.

Thanks

 

[JB]

Re: Actual HP of Small outboards or Kickers

Generally, outboards are advertised at the HP rated by the engineers with a prototype. . .+/- 10%. Manufacturing tolerances cause any given outboard to fall into that +/- 10%. Only the most modern, computer managed machine tools turn out outboards that are consistently any closer than that.

NMMA won't allow makers to outright lie about the power of their products.

 

[Silvertip]

Re: Actual HP of Small outboards or Kickers

Although I don't have documentation to this effect, I've read that manufacturers must abide by a 10% (plus/minus) HP rating. If they sell a 9.9 it cannot deliver more than 10.89 HP nor less than 8.91 HP. In reality, no two engines from the same manufacturer will likely deliver the same exact HP simply due to manufacturing tolerances. An engine on the tight side will likely deliver less HP. An engine on the loose side and it will likely deliver more. Will they last the same under identical operating conditions is debatable.

 

[Chinewalker]

Re: Actual HP of Small outboards or Kickers

Also, as Mercury used to state in their old brochures, horsepower varies with RPM. Very few kicker motors are really dialed in the way they should be. Can't tell you how many times I've seen one guy complain that his 9.9 was slow while another guy's 9.9 ran by him. Turns out the first guy has a sailboat prop on his, while the second guy has a prop that actually works well with his rig. Same thing happens with larger rigs, too, but small boats are much more sensitive to stuff like that so the problem is often more apparent. Take the time to match the prop with the application to get the motor's RPM into it's recommended range and you'll have a better performing rig, whether it's a light tinny or as an auxiliary on a larger boat. The half horsepower either way makes much less of a difference than proper set-up....
- Scott

 

[TOHATSU GURU]

Re: Actual HP of Small outboards or Kickers

The government ratings for tested hp are available from www.epa.com.

 

[pvanv]

Re: Actual HP of Small outboards or Kickers

I think there's a slight typo... I believe the website is http://www.epa.gov/

Keep in mind that years ago, there was the disparity of Gross horsepower vs Brake horsepower. At that time, some import ob's of similar hp ratings were actually higher output than the US motors, because they were rated at the prop, vs the old us standard of rating at the crank. There can be a 10% hp difference due to transmission losses in the LU, etc. Due to government certification, this is no longer the case.

That said, with epa dynamometer certification of output (at the prop), the motors are pretty much as advertised. Really. A new 9.8 does indeed make about the same power as a 9.9, though built on a completely different powerhead. They have different power curves, but the max output is almost exactly what is claimed on the sticker.

The old OMC 9.9's were detuned 15's "in sheep's' clothing", but that approach tends to be less efficient than designing a motor from the ground up for a particular hp. The same is true of the carbureted "families" of motors, such as the Tohatsu/Nissan/Mercury 4/5/6 hp motors, where the primary difference is in the carburetors. The 4 hp unit does make less output than the 6, but it does so with a loss in volumetric efficiency -- similar to the old 9.9/15 situation.

Long story short, we can rely on the stickered hp ratings today.

HTH

 

[Boatist]

Re: Actual HP of Small outboards or Kickers

Thanks Everyone for the information.
I guess what confused me was information about my current kicker.
A Johnson 1975 15 HP 2 stroke. I bought it the second year it was out and it was rated as 15 HP.
About 3 or 4 years later they redsigned the head and said it had 10 percent more power and less likely to foul the spark plugs but still rated as a 15 HP.
Later they made more changes to the Carburator and Exhaust tunning and said it increased power by 22 percent but still rated at 15 HP.
Also twice they changed the Points, condessor, flywheel and ingition coils and also said it started faster and had more power but still 15 HP rating.

One of these redesigns I am sure was when the changed power ratings. Old HP rating was from the Power head and later changed to the Prop shaft. The other changes more about easy starting and reliabality with a little sales hype thrown in.

Kicker motors will most likely never be run at WOT where you reach the Max HP. I know my motor which started as a short shaft motor on a 14 foot Klamath Aluminum boat was run at WOT a lot. When I put it on the 21 foot aluminum boat and converted to a long shaft I do not think the motor ever was ran over 3000 rpms.
I changed from the standard 9 1/2 by 10 pitch by 3 blade to a 9 3/8 by 9 pitch by 3 blade Stainless Steel while it was on the 14 foot boat and it made a big difference. When I moved to the 21 foot boat it still worked well in foward but could not even back up into a 15 mph wind.
I changed again to a 10 inch by 9 pitch by 4 blade high thrust prop that also has exhaust relief and it would back up great but in foward if went to WOT it would load up and die. At mid range it would run ok.
Last I put on a 10 inch by 7 pitch by 4 blade high thrust prop and it was near perfect.

Today I would like to go with a 4 stroke Electric start 20 HP but since it is on a lift bracket need to control the weight.
The Honda 20 HP is the lightest of the 20 HP 4 strokes but when you get Electric start then they only come with POWER Tilt and Trim and that adds 31 pounds.
The Honda 15 HP Electric you can get without the power trim and tilt so lighter. Also can get with a 25 inch shaft.
The SALEMEN I have talked to have been telling me the low end torque and HP are almost identical between the 15HP and 20HP But then they are Salesmen and will make money off the deal.

At this years boat shows I hope to find some Honda factory Reps and find out a little more before making the decision. I will be careful how I ask the Questions so as not to give away the answer I am hopeing to get.

Again Thanks Everyone.

 

[pvanv]

Re: Actual HP of Small outboards or Kickers

Nothing against Honda, but you may also want to look at Tohatsu/Nissan/Mercury (all the same motor, different stickers, brand recognition, and pricing -- Tohatsu least expensive, Merc most expensive, Nissan in between).

The 15/20 motors weigh-in at 114.4 pounds in short shaft without power tilt/trim/etc. The spec sheet is available at http://tohatsu.com/outboards/20_4st_spec.html The electric start, short shaft, tiller steer, 20 hp Tohatsu has a retail price of about $3289.00, which is a lot cheaper than a Honda 20. These motors have automatic enrichment (no choke needed), yet are simple carburetor setups, without the complexity of EFI. The 2009 models have gas-assist tilt (less weight, no power needed) standard.

I service a fleet of Tohatsu/Nissan 15's that are constantly beaten up -- annual prop replacements from groundings are not unusual -- and they are extremely reliable and durable.

FWIW, I run my Nissan 9.8 4-stroke at WOT all the time. It pushes an 8,000-pound sailboat pretty well with a high-thrust, 4-blade, exhaust-relieved prop. Lots more low-speed thrust than my old mid-70's 'rude 15, and great reverse. As you noted, the key is correct propping.

 

[gss036]

Re: Actual HP of Small outboards or Kickers

I ran a early 90's Johnson sailmaster w/25" leg for several years and it worked great, then my WIFE was with me at a boat show and saw and heard the HONDA 15 hp run, the first words out of her mouth was buy, so, I said yes dear and have been running the 1997 Honda since then. I am considering buying a new kicker and will probably go with the 9.9 HP as I don't think you need any more for trolling and emergency use. You can only go so fast w/a kicker because you can never get your boat up on plane w/it. My 15 hp pushes my Seacraft 23 WA a max of 7-8 mph @WOT and will troll all day w/o any problem. I have had to go as far as 15 miles on the kicker and did so at about 5mph for the 3-4 hours it took to get back to the harbor after blowing my big engine.
Keep us posted on what you find out. I would be interested in knowing, maybe even changing my mind. I just repowered w/ a 225 Honda, so the next kicker will probably be my last also, as I will soon be 66 yoa and it should last as long as I want to fish.

 

[ondarvr]

Re: Actual HP of Small outboards or Kickers

Around this part of the world the most popular kicker by far is the Yamaha T8, even on boats much bigger than yours. A few people use the 15 or 20 HP high thrust models, but not many. The T8 will have far more thrust than your current 15, use less fuel and will be very quiet.

 

[gss036]

Re: Actual HP of Small outboards or Kickers

I have seen a few used T-8 advertised (Yamaha T8 Outboard - $2075),but they want as much as a new one. I haven't priced a new T-8, how are they?
I didn't mean to high jack your thread, sorry.

 

[ondarvr]

Re: Actual HP of Small outboards or Kickers

I was actually replying to Boatist, but it applies to both of you. I don't know what the current cost new is, but the resale price is high.

 

[jspringator]

Re: Actual HP of Small outboards or Kickers

I don't know anything about a Yamaha T8, but I just bought a Yamaha 15 MSH 2 stroke. 79 pounds and very easy pull. Definately won't need electric start. Idles very well, even with the 24 to 1 break in mix. Will run on 100 to one, whch I guess would be ok in the except at the end of the season.

 

[Boatist]

Re: Actual HP of Small outboards or Kickers

Ondarvr
You say the Yahama T-8 will have more thrust than my 15. That is one of the reasons I started this thread as I have heard many say that. I feel and most here have said 8HP is 8 Hp and 15 is 15 and 20 is 20hp. So If it has more power and the right prop how does a 8 HP out perform a 20 hp? Lots of Yamaha Salesmen say that.
I know it has a much different gear and a large flat prop but it is tilll only 8 HP.

Jspringator
My current 15 is a roap start and weighs 74 pounds. When it was on the back of my 14 foot aluminum boat I felt I did not need electic start either.
However now it on a lift bracked and in the ocean when it most of the way down to start it must raise up so can pull the roap somewhat straight, then put it back down. Also as I get older starting to lean more to electric start.
Another factor is electric start models can charge battery. Some Roap start have some battery charging but usually no more than 6 amps even at high rpms.

Last year was the first time in 28 years my main motor shut off. We were in our fifth day in the ocean and only about 6 miles out of port and it just quit.
So I started the kicker and put the wife on the wheel and told her to start in then opened the motor cover to start trouble shooting the problem. I found it had fuel but no spark. Went to get out the tool box and see the wife is headed straight toward shore. I stopped an ask her what she was doing and she says heading to shore. This shore is not a freindly shore nothing but big rocks and 100 foot high clift. So explained to the wife right now the shore is danger. Much better to be floating 2 miles offshore than slamming into the rocks. She change course to head along the coast and go in the way we normally would. I then checked the points and could see they had a problem. I think I could have just cleaned but instead change to a new set that I carry. Set the gap by eye and had the wife start it up. Shut off the kicker and closed up the engine then headed back to where we were going to fish. Took about 10 minutes to get back under way.

The whole thing got me thinking. Had I had a heart attack or been hurt could the wife have started the kicker? If it had been a harder problem and had run down the battery or something I would have no way to charge the batteries. So this is why I want a Electric start.

Also would like to get rid of that 6 gallon fuel tank and run the kicker off the main tank. Wife and Son offten complain about the smoke form the 2 stroke motor when use to back into the wind.

Several motor several years ago tried going to 100 to one oil mix but I think they all went back to 50 to 1 mix. I ask OMC/Johnson about the 100 to 1 mix and they said is fine for trolling but not for high speed.

 

[pvanv]

Re: Actual HP of Small outboards or Kickers

The low speed thrust of a small Yamaha (or other, such as Tohatsu/Nissan/Merc) is pretty much because of the High Thrust prop, though there are also sometimes minor gearing differences. Think barge or heavy sailboat. Solas makes them in 4-blade, low-pitch form. Some of the motor companies sell them re-badged under their own labels.

They are all good motors. In your case, a 4-stroke should be considered -- to get away from the premix smoke, and for the convenience of running from the main tank. I think that dealer convenience, honesty, and performance is as important as the motor itself. From a price/performance standpoint, if you have a Tohatsu/Nissan dealer nearby, it would be worth investigation. Those 8/9.8 motors compete with the others quite well, and are lower priced.

 

[gss036]

Re: Actual HP of Small outboards or Kickers

Electric start is the only way to go. It gives you more spins and continous, so starting is (or seems to be) more assured. I have only had one pull start and that was way back in the 70's. I bought a new 9.9 Evinrude w/ electric start by accident, Only one they had. Truly I would not have it any other way. Yeah! I am still looking, but really not in a hurry.

 

[ondarvr]

Re: Actual HP of Small outboards or Kickers

High thrust models have a totally different gear case with lower gearing, plus the prop is much larger and of a totally different design. Nobody said it would be faster than a 15, just more thrust, like low gear with great traction on a 4X4 compared to third gear in a sports car, not more speed, just more pulling power and grip. A 20 or 30hp motor won't plane your boat and neither will a T8, you'll only get it up to 7 to 10 mph and the T8 will do that. Reverse will be better with this type of prop also. Every fishing boat in the NW is equipped with a kicker, the T8's are considered the gold standard of kickers here and there's a reason for it.

 

[Boatist]

Re: Actual HP of Small outboards or Kickers

I have looked at the Yamaha T8 in the past. The ones I saw also had power tilt and heavier than my motor. I have a 10 inch by 7 pitch by 4 blade prop that has exhaust relieve and it back up very well into strong winds.

Right now I am mostly looking at the Honda BFP 20 and the Yamaha F20.
I use this kicker mostly offshore in seas to 8 feet every 8 seconds and winds to 38 plus common. My current motor works well but would like to go 4 stroke electric Start.

Only problem I have with my motor is in big swells if have to turn up into the wind and swells it turn slower than I would like.

I have really always been a Johnson / Evinrude / OMC fan, but OMC gone and Johnson/Evinrude do not make a 4 stroke 15 or 20 hp motors anymore. One thing I always liked about Johnson/Evinrude/OMC was you could buy parts at so many dealers. Even today I think there are still more places to buy Johnson/Evinrude parts than any other in my town.

 

[gss036]

Re: Actual HP of Small outboards or Kickers

I don't like going out in that type of water, but I think I am with you on the idea of something to get up and over the swells. The Honda 20hp is the same basice engine as the Honda 15 hp. They do something with plate behind the carb to restrict air and fuel flow to bring it down to 15 hp. The 20 hp would be my choice in those situations. Up here the PNW we have to deal with 3-6ft short chop becaue of the depth and islands.

 

[Boatist]

Re: Actual HP of Small outboards or Kickers

Thanks for the Reply GSS036
Yes the Honda 20 electric start is what I would like to get. I have tried to do that for the last 2 years. Motor is near $3K but I do not want the extra 31 pounds of the power tilt and trim. The way My motor is mounted the power tilt and trim is just extra weight to me. My kicker bracket is actually 2 lift brackets rated for up to 20 HP that I joined together but still even with my 74 pound motor you have to lift pretty hard. You can see a picture in one of the early posts. If I just relese the latch the motor will go down about half way. To get all the way down have to push down. From all the way down if relese will come up about half way then must lift.

On other motor I know that share the same Cubic inch power head but have two different HP like the Johnson 15 I own and the Johnson 9.9 the difference is in the Carburator and the exhaust.
The carburator Has a bigger bore and will let in more air and fuel.
My feeling is at half throttle and below both motors put out the same power.
At half throttle the throttle plate is what restricts airflow into the cylinder not the carburator Bore or venture. At WOT then the size of the carburator bore and is the airflow restrictions and the bigger bore would produce more airflow and fuel to generate more power. At High RPM levels the Bigger bore and larger eshaust header would allow to produce more HP.

Thing is I normally am running at just over idle speed. Another factor is the 15 can get with a 25 inch shaft and electric start with out the power tilt and trim. Off shore this would allow me to keep the prop in the water without the power head going completely under the water on the big swells.

I still suffer from sticker shock, My 15 HP I got for $600 but now a 4 stroke 15 is almost $3000. My old motor still runns near perfect and starts the first or second pull most of the time. It usually starts on the first pull but I can not get to the choke in time to push it in before it stalls. So push the choke in and pull again.

My motor does have one problem I have not found a fix for. Each cylinder run best at a different carburator adjustment. If I run on one cylinder and adjust the best idel and low rpms then switch to the other cylinder it will not even run. So I have to adjust to half way in between to get both cylinders to fire evenly. I know one cylinder has 5 more PSI when I do a compression test but do not know if that is the problem or just the fact that one has to lift the fuel higher. Anyway I still love that old 1975 15 hp Johnson but feel I should replace.
I feel the Honda 15 and 20 Hp would be the same power also at half throttle and low RPMS but since it rated at the prop Shaft and My 1975 15 was rated at the power head the 15 HP Honda likely has 20 percent more power. also with much more Cubic inches and a longer stroke should have more low RPM power.