Old HP versus new HP

[carbineone]

This may be interseting and have always kinda wandered if the
older HP rating say from the late 50s early 60s
versus the later engines HP ratings.I know alot of older engines of all types were maybe rated differantly in the old days
for some reason.Just curious how old HP ratings are done on later motors as opposed to the newer HP ratings.If any differance at all or maybe the system has always been the same for Outboards..

 

[JB]

Re: Old HP versus new HP

Up until the mid 80s outboard power was measured at the flywheel. After that it has been measured at the prop. The difference is usually about 5-10% of flywheel HP.

 

[carbineone]

Re: Old HP versus new HP

So I assume you are saying the older ones that were measured at the flywheel are maybe actually 10 to 15% less than rated when compared to a new one of the same HP? Kinda like the old HP in cars being meusured at the crank instead of at the rear wheels?

 

[ChrisAG]

Re: Old HP versus new HP

Yes - except that no automobile manufacturer measures hp at the wheels.

 

[carbineone]

Re: Old HP versus new HP

Thanks,no I did not figure that the manufacturers dynoed the cars to meausure actual HP at the wheels..Another question than maybe.I know the older motors appear to be humungous compared to the same modern ones with the same rating.So I assume the older motors are much heavier than the newer ones too with the same HP?

 

[ChrisAG]

Re: Old HP versus new HP

In some cases yes; it really depends. Some of those old motors were fairly light despite the bulk. And now 4-strokes have the extra weight of a valvetrain and crankcase oil. Modern 2-strokes like Evinrude E-Tec are a bit heavier than carbureted 2-strokes due to the heavy magnets required for the direct injection. The benefits of better fuel economy and emissions.

However, let's say you are comparing an old V-4 90 to a modern inline-3 90. Depending on the year, the new one might be lighter (and certainly more compact). Again, it depends on many things.

 

[aganser]

Re: Old HP versus new HP

Not really so. Most older ones are lighter. Newer motors are more complex (4 stroke, 2 stroke EFI or DFI) and have grown a little portly as a result.

Bob

 

[JimS123]

Re: Old HP versus new HP

Up until the mid 80s outboard power was measured at the flywheel. After that it has been measured at the prop. The difference is usually about 5-10% of flywheel HP.

That;s why there was often a noticable difference in the old days. Prop shaft standardization was instituted by the boating industry and it put everybody on equal ground.

Mercury was noted for rating at the prop shaft, then cheating besides. They got their reputation as the fastest outboard because a 10 hp Merc was actually 12 HP. Hard to compete with a 10 hp Johnson.

Then in the 80's they maintained their reputation simply becasue they offered bigger motors than everybody else.

 

[carbineone]

Re: Old HP versus new HP

So Mercury was using the prop shaft to determine HP and thus everyone else was using the flywheel on top and this of course gave them a lower reading doing it down below?So in otherwards you are saying they really had a 12HP if they would have meausured it at the top flywheel like everyone else..That is Cheating.

 

[JimS123]

Re: Old HP versus new HP

Well, the people that bought Mercs didn't think it was cheating....LOL.

As a kid I had a 10 HP Evinrude and my buddy had a 10 HP Merc. He ALWAYS beat me on virtually the same boat. But I always got the last laugh.....eventually he would break down and I was still going.

 

[carbineone]

Re: Old HP versus new HP

LOL.yes the extra 2 horse would be worthless if it will not go...

 

[OldMercsRule]

Re: Old HP versus new HP

Mercury did underate their engines in the 1950s, 60s 70s and 1980s.

Dunno 'bout the newer engines.

Sometimes they underated a little, sometimes a lot.

I own and run inline6s which are pound for pound the lightest relatively highpower production made outboard engines ever built.

Example: My 99.x cubic inch 1977 Mercury 1500 puts out 150 HP at the crank @ 5800 RPMs and only weighs 270 LBS.

Nearly the same engine was re-rated in 1982 at the prop to 115 HP (and that engine did not loose anywhere near 35 HP through the gear box).

Me overpriced $.02. JR

 

[steelespike]

Re: Old HP versus new HP

As suggested the older motors were simpler.The 58 Erude 4 cylinder 50hp short shaft was about 200 lbs,todays Erude etec 2 cylinder 50 is 240 lbs but it uses a little over 1/2 the fuel.The old 50 was a terrible hog.optimistically rated at 6 gallons per hour probably closer to 7.Etec 50 runs a little over 4 gallons per hour.

 

[pecheux]

Re: Old HP versus new HP

Odly enough, when I was a teenager (and 140 pounds .LOL) my dad owned a 14 footer made out of wood pushed by a 15 hp Evinrude ... and we could water ski behind it.

I cannot see any late model 15 hp (any brand) that could do such thing ...

 

[JimS123]

Re: Old HP versus new HP

Odly enough, when I was a teenager (and 140 pounds .LOL) my dad owned a 14 footer made out of wood pushed by a 15 hp Evinrude ... and we could water ski behind it.

I cannot see any late model 15 hp (any brand) that could do such thing ...

Ain't that the truth. I firmly believe that we have not gotten any smarter these days, we just are more willing to throw cash at the boat rather than trying to optimize it. Nobody is ever satisfied unless they have the biggest and newest engine in the back.

When we waterskiid in the 1950's we used a power prop. If we wanted to go fast we switched to a speed prop. Most engines will do what you want with it if its propped right (within reason).

You may be right about the current motors. All I can say is that I cant's see much difference between my 2007 25HP and my '52 25HP, except its quieter and makes a lot less smoke...LOL

 

[steelespike]

Re: Old HP versus new HP

Probably difficult to realize the difference but the 52 was rated at about 2 hours on 5 gallons.Would do about 30 on a fast boat.The 57 35 hp was rated at 1 3/4 hours on 5 gallons.at about 33 on a fast boat.Your 2007 25 is probably about 1 3/4 hours
at about 32mph. Just splitting hairs.That old formula of gallons per hour = to 10% of the hp is still pretty much the same.

 

[JimS123]

Re: Old HP versus new HP

Coincidentally, last summer we took rides in both boats on different days over the same course, so I can give a rough comparison of fuel usage. The ride included about 6 miles on a canal at 6 mph, then ~3/4 throttle in the river for 6 more miles to the fishing spot. And of course the return trip. Total running time 2 1/2 hours. Weather virtually the same.

The '52 is on a 15 wooden lapstrake boat, V bottom. The '07 is on a 14' aluminum boat, deep V. The woodie has about a 50# weight advantage acoording to mfg's specs.

The '52 consumed about 7 gallons and the '07 exactly 3.

 

[Isaacm1986]

Re: Old HP versus new HP

Yes - except that no automobile manufacturer measures hp at the wheels.

Actually every auto maker in the UK measures HP at the wheels, it is called BHP, Brake Horse Power.

 

[achris]

Re: Old HP versus new HP

Horsepower is the amount of work done in a given time... I could find the exact numbers but that's irrelevant. The point being that it doesn't matter whether 25hp is being produced by a 1952 2 stroke, a 2010 4 stroke or a 1836 steam engine.... 25 horsepower is 25 horsepower...

What has changed is the efficiency and reliability of those engines.

Example....

My father owned exactly the same boat as I currently own, and it had a 1970 Mercruiser 165. It was at the mechanics shop about every 6 moths for the 8 years he owned it. I had a 1994 4.3LX in mine before I changed it to the current engine and in the 12 years I owned that engine I had 3 significant problems with it. (Rusty sump, rusty ignition coil and the flooding carb, which I never managed to rectify).

I had an old inline Merc 150 on my first boat, and it was a nuisance, great when it ran, but needed to be constantly looked after. I sold it and put a newer Merc 70 on the boat. That engine never gave me any problems in the 4 years I owned it.

I could go on, but you'll be glad to hear that I think I have made my point.

Chris..........

 

[CaptainHook]

Re: Old HP versus new HP

So then your saying that if my boat was a 1975 and was rated for 150 hp max and I put a brand new 150 hp motor on it I would now be over powering the boat??????