Old Outboards; how many horses escape over the years?

[ronsealdeath]

Hello, just out of interest;

Has anyone got any idea how much power a 2-stroke outboard would lose over time?

My 1977 Evinrude 55hp may well have produced 55hp at the crank in 1977 but how much would it produce now?

It would be interesting to see if anyone has ever 'dyno' tested an old outboard to check this out. I know outboards were power rated from the prop in the mid 80s so I am guessing my motor in modern terms would ideally produce about 45hp at the prop but over time it must be less than that surely?

What causes this power loss? Bore/ring wear and compression loss? Carbon build up? Spark strength? Or a combo of lots of wear and tear on ignition, fuel and mechanical systems!

Thanks
Al

 

[robert graham]

Re: Old Outboards; how many horses escape over the years?

My guess is that a well-maintained outboard motor with smooth cylinder bores, carbon-free piston rings and exhaust ports, etc. would crank out about the same HP now as it did several years ago. I feel like most 2 stroke outboards will die of something besides warn out bores/pistons/rings. In fact, I'd be interested to hear from anyone who has just plain warn out an outboard motor. I believe that fuel-related problems, like plugged jets, etc. causing lean fuel mixtures may fry more motors than just wear and tear. It's an interesting subject!

 

[JB]

Re: Old Outboards; how many horses escape over the years?

I never saw a worn out outboard. They all die of neglect and abuse or catastrophic part failure.

 

[Silvertip]

Re: Old Outboards; how many horses escape over the years?

The answer to this question is simple. Can you run as fast as you could when you were 16 years old? Are your eyes as good as they were 20 years ago. You see -- how people treat things (including themselves) determines how they get through their life. Some folks have the ability to allow all HP to escape in a week, hours, or a few days through sheer ignorance or neglect. Others can run an outboard for decades with no issues and the engine would still deliver nearly full power. Things "begin" to die the minute they are born. The rest is a crap shoot.

 

[ronsealdeath]

Re: Old Outboards; how many horses escape over the years?

Its certainly true that the old 2-strokes out there are more likely to be the ones that were looked after well, at least for most of their life. The 2-stroke design is relatively simple so I guess they are more likely to last that bit longer but they are arguably easier to treat badly if you get my meaning. Pre-mixing fuel means you are prone to making the odd mistake or for a VRO to fail then it all goes bang!
One could perhaps assume then if you took my outboard that has a clean set of carbs, new plugs, good spark and runs well then gave it a good de-carb and used fresh fuel with decent TCW3 then you could expect to get near to factory HP assuming compression was up there? Simple assumption I guess but then a 2 stroke hasn't got much more to it?
Anyone out there tested HP on their outboard?
There is a site here in UK that deals in old British Seagull parts (I have a Silver Century 4-5hp as an aux) and the chap who runs that has tested thrust on old seagulls and has found the 4-5 hp models barely make 1hp! I'll try and find the link if I can.

update

here you go, in the section on horsepower
http://www.saving-old-seagulls.co.uk/i_d_your_seagull/i_d_your_seagull.htm

 

[robert graham]

Re: Old Outboards; how many horses escape over the years?

I just don't see a good, well-maintained 2 or 4 stroke outboard motor giving up much of it's horsepower just due to it's age or normal use. I'm still running a 1990 3HP Tanaka motor and it still makes the same power it always has. My 1999 90HP Yamaha 2 stroke still jerks my boat up on plane in just a few seconds. Now if either of these had specific mechanical problems or issues then I'm confident I'd feel it in the running. I guess a Yamaha dealer could put a test prop on the motor and run some kind of "dyno" on it, but I don't know. Good Luck!

 

[dingbat]

Re: Old Outboards; how many horses escape over the years?

I have my 200Hp Evinrude performance tested every spring for the past 5 years. Tests include compression and leak down tests as well as being run on a dyno.
The motor when I started this regiment 5 years ago the motor had just a little over 1500 hours on it. The motor had a little over 2500 hours on it went in for this spring testing.

First year compression, all 6 cylinders between 91 and 97. It put out 215 HP on the dnyo. This year, all 6 cylinders between 90 and 95. It put out 212 HP on the dyno. While in for testing, the mechanic found a lean pop at idle and the head gaskets where seeping from an erosion problem in the block in the area of the head gasket which we had tried to addressed the year before. Instead of tearing off the intake manifold and rebuilding everything from the inside out, I decided to just have the power head replaced.

New power head, all cylinders 100-105, dyno at 218 HP with 10 hours on a new power head. The excess oil and fuel in the exhaust is notably less than before.

So yes, they can and do wear out if you put enough time on them. The average boater puts less than 50 hours a year on a motor. At that rate, this motor had over 50 years of use on it.

 

[nwcove]

Re: Old Outboards; how many horses escape over the years?

i dont run big motors, but i do run a 1985 evinrude 4.5 and a 1957 johnson 5.5, on the same boat, the 85 rude has very low hours and works like the day it purchased, the old johnson has unknown amount of run time. the 5.5 will run circles around the 4.5! can 1hp.....being 28 years older, make that much difference? like all things mechanical, they have to wear out......but good maintenance should keep em running for a long long time.

 

[Silvertip]

Re: Old Outboards; how many horses escape over the years?

The comparison is NOT just 1 HP. The 5.5 has 20% more power than the 4.5 so yes -- 1 hp does make a difference. You can look at this another way and compare a 100 HP engine to one that delivers 120 HP which is also "just" a 20% difference.

 

[nwcove]

Re: Old Outboards; how many horses escape over the years?

with all do respect......shouldnt the "wear factor" come into play? ......its actually only 18.2% more hp. lol but i do see your point.....a 1hp motor will turn circles around a boat adrift with no motor!! 100% more power.

 

[fucawi]

Re: Old Outboards; how many horses escape over the years?

your reference to the british seagull is not relevant....they only produced 1 hp when new but were geared down to produce the same thrust as a 5 hp ....but that meant only 5 mph

 

[nwcove]

Re: Old Outboards; how many horses escape over the years?

are you confusing torque with thrust? or are they one and the same? (probably a topic for another thread! lol)