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Author Topic:   History of 300-HP Engines and the Ten-Percent Rating
L H G posted 10-11-2007 07:31 PM ET (US)   Profile for L H G  
As "Plotman" brought up on the 300 E-TEC discussion, the 300-HP threshold in outboards has been a moving target for many years. The 10% rule has allowed the companies to take liberties with the consumer, a really poor situation I think. It does need to be changed by the NMMA, even though it is not in their interest to do so. As buyers we should get close to real HP we are paying for, manufacturing tolerances accounted for, never less. If they want to give us a little more, well that's OK. It's why I buy Mercs. Most are conservatively rated, a company practice for years and years.

I think it all began with the 3.6 liter OMC V8, which began production introduced with a 300-HP decal. Then it dropped down to a 4.0 liter 275 Model as the 300 threshold was being questioned. I believe the engine never really produced anything close in prop HP, as it ended production as a 4.0 liter 250 prop HP model, also a stretch, in relative disgrace as fuel pig and average performer, expensive to maintain. Whaler put some on 27's in the form of Sea Drives, and they disappointed from what several dealers told me. In staying competitive, Mercury came out with a 76 degree V6 3.4 liter engine, initially at 300HP, and quickly changed to 275HP. These would run with the V8's, or better, but were also fuel guzzlers and had a short production life. Then the much smaller 60 Degree Merc 3.0 liter engine came out in 1994, to this day a hot performer, which effectively ended the period of the V8 and 3.4 Merc V6. Modern design proved that a much smaller block, and more compact 60 degree balanced engine design, could outperform these earlier large monsters. Merc even advertized that the much smaller 225 EFI (actually about 240HP) could outperform the OMC V8's by 5 mph on an offshore boat, and get better gas mileage while doing it. They did. So much for the true 300 threshold, never really attained.

Then Mercury brought out the "Darth Vader" 300 EFI, still based on the 3.0 liter block, which became quite popular with the performance crowd. It was the stongest recreational outboard avaiable for several years, until Yamaha came out with the 300 HPDI, a badly troubled engine initially. But the Bass and Walley magazine guys did a test of the Merc and Yam 300 HP offerings, and found the Merc EFI dyno-ed at 277HP, while the Yammie turned out 275HP, an engine still being offered today after several "fixes". So still, after 20 years, no real 300 HP at the prop outboard. I did read somewhere that the 275 Verado does dyno at 275 true HP.

That is why, when Mercury finally introduced the 300 XS Optimax a year and a half ago, they advertized it as the first REAL 300 HP engine, with dyno tests showing 310HP. Now we have the newly introduced 300 Verado, as of yet with no real HP testing, except to assume that the Verado platform, with the supercharging and fuel mapping and new pistons, probably makes a true 300 easily feasible. We also have the new large cube 300 Suzuki, probably a true 300 because of the 4.0 cubes, but as yet unknown in true output. Then, finally, this new E-TEC, not yet on the market, to see what it really puts out, and whether it is 300 horses or only 300 decals. I'm still betting about 275HP, causing the E-TEC gods to be howling at the moon!

And latest, Yamaha has hopscotched the whole group again, upping the anti, with the V8 350, starting another "arms race". Supposedly, Merc has a 350 Verado due shortly also. So once again, the big boys in the outboard field, with the transoms to make it work, are in the HP lead again. And all the while, this becomes of little interest to owners of Classic Whalers.

jimh posted 10-11-2007 08:39 PM ET (US)     Profile for jimh  Send Email to jimh     
There is no "ten percent" rule. The ten percent variation only applies to manufacturing tolerances for production motors. The rated power is limited to six percent. Read the industry standard:

and show me where it says that a manufacturer can rate the motor ten percent higher than its actual horsepower. It does not allow that. The "rated power" is recommended to be presented so that there is no more than a 6% difference between the rated power and the peak power which occurs in the full throttle speed range.

Furthermore, emission regulations are all based on a certain amount of emission for a certain horsepower. If manufacturers can easily "dial up" the horsepower (for marketing purposes) they would also be able to increase the allowable emission output.

I don't know what used to go on in the 1960's. But this is 2007. The rules are not the same. Is there really a ten-percent tolerance in effect now?

Peter posted 10-11-2007 09:51 PM ET (US)     Profile for Peter  Send Email to Peter     
Larry it seems like you frequently like to dig yourself into a factless hole. Let me help you out of it with some real established facts.

The 3.6L OMC V8 was released in the 1985 model year in two model forms, a 275 that could be had with 20 or 25 inch shafts and a 3.6 GT (Johnson) or XP (Evinrude) which came only in a 20 inch shaft length. The 275 was rated 275 HP at 5500 RPM and had an operating range between 5000 and 6000. The 3.6 GT/XP did not have a specified horsepower but its operating range was 5750 to 6250 RPM and a published power curve suggests 300+ HP at 6250 RPM. The 3.6 GT/XP differed from the 275 in that it had an exhaust exit above the anti-vent plate.

The 3.6L V8 offering (275 and 3.6 GT/XP) stayed the same for model years 1986 and 1987.

For the model year 1988, the displacement of the V8 was was bumped up to 4.0L and two products were offered, a GT 300 or XP 300 and a 275. The 300 had an operating range of 5000 to 6000 with 300 HP at 5500 RPM instead of the narrower 5750 to 6250 RPM in the 3.6L block. The 300 could now be had in a 25 inch shaft.

In 1989, the 275 was discontinued but the GT/XP 300 model remained. The 300 could be had in either a 20 or 25 inch shaft. The same offering was made in 1990.

From 1991 through 1995, a 300 and 250 V8 were offered. The 250s operating RPM was 4500 to 5500 with 250 HP at 5000 RPM.

So, now that you have the real, established facts, would you like to retell your story? ;)

L H G posted 10-11-2007 11:05 PM ET (US)     Profile for L H G    
I appreciate the OMC facts Peter. Thank you for adding that information. But none of those give the engines 300 HP at the prop, which is what my story is about. Decals were cheap back then. Also please tell us why OMC discontinued these "powerful" engines, abandoning the performance market to Mercury. Loss of the V8's left them with only the 225 3.0 liter engines to sell.
L H G posted 10-11-2007 11:38 PM ET (US)     Profile for L H G    
Jim - somewhere recently in a post, XSTECH, who I assume works in the Mercury Racing division on the XS Opti's, indicated in a post that the 10% rule still applies in leeway to the manufacturers in rating HP. Maybe a search will turn up his post. It was regarding the 225 HO Evinrude.
L H G posted 10-11-2007 11:45 PM ET (US)     Profile for L H G    
Jim - One more thing. For some time now, OMC specialist 1st class Peter, has been telling us the Evinrude 225 HO is 245HP. How does that happen under YOUR rule? Maybe Peter can help us out also.
Tom W Clark posted 10-12-2007 12:01 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Actually, Larry, the 300 HP OMC V-8s were 300 HP at the prop per then current BIA certification standards.

I found this photo in another thread and it is great:

Does anybody else remember this motor? This has got to be the circa 1980 and Mercury was playing catch up with OMC. I remember hearing the rumors around this motor but it was never brought to production because all the prototypes kept blowing up! Very cool to see a photo of it though.

In fairness, it should be pointed out that Mercury was finally able to come out with a 275 HP motor using a fancy Cosworth engine block. These motors did not have a much better reputation. Friend's of mine on Cape Cod had one and it lasted three years before throwing a rod one month after the warranty expired.

Kingsteven18 posted 10-12-2007 02:17 AM ET (US)     Profile for Kingsteven18  Send Email to Kingsteven18     
I have a lower unit for one of those Evinrude/Johnson 300's or whatever they are if anyone is looking to buy one.
jimh posted 10-12-2007 07:23 AM ET (US)     Profile for jimh  Send Email to jimh     
The Evinrude 225 H.O. is not sold with a horsepower rating. It is sold with a kW rating that converts to about 247-HP. But there is no horsepower decal on the side. It says "225 H.O." not "225-HP". It is not an exception to the ICOMIA 28-83 rating rule.

When Peter mentions the figure of 247-HP he is relying on the information provided by the manufacturer on the emission certification label and in the emission certification testing data from the EPA. The equipment which measured this horsepower is carefully calibrated and certified for making precise measurements of power and emission.

When LHG cites horsepower figures for Mercury motors I am not sure what is the source. I think it would be very helpful if the source of all of the test data which shows how much more powerful the Mercury motors are could be disclosed. If there are published test data which show that Mercury motors are more powerful than their claimed horsepower denotes, I would like to read the data and see the test results. And I would like to know the details of the testing, and if all the variables were as controlled as in the official tests of engine power and emission to which the Evinrude motors have been qualified and measured for horsepower.

Also, I have to note that Evinrude has published horsepower curves for their motors and compared them with four-stroke competitors. I do not recall seeing any horsepower curves published by Mercury.

Peter posted 10-12-2007 08:23 AM ET (US)     Profile for Peter  Send Email to Peter     
Jim -- You beat me to it. I was going to mention to Larry that the propshaft HP declaration for the 225 HO is "Factory Tuned for High Performance" which seems to be no declaration at all. The 184 kW number (247 HP) comes up because they do need to tell the EPA what the output of the motor model is for emissions certification and compliance purposes.

Like the 225 HO, the HP declaration for the E-TEC 200 HO is "Factory tuned for High Performance". I have heard but cannot confirm that the 200 HO is good for about 220 HP.

The standard E-TEC 225 has a propshaft HP declaration of 225 HP at 5150 RPM which is in the middle of the 4500 to 5800 RPM operating range. Evinrude has published a power curve for the 225 and the curve shows a peak HP of approximately 238 HP which is 6 percent above the declared HP.

Thus, by not declaring a propshaft HP, one can apparently escape the 6 percent rule of ICOMIA 28-83.

JMARTIN posted 10-12-2007 12:22 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
Hey, in the pictures of the old 300, is that not, the Snowman? John
blkmtrfan posted 10-12-2007 01:49 PM ET (US)     Profile for blkmtrfan  Send Email to blkmtrfan     
Yes John that is Jerry Reed

Larry, to clarify HP of the 3.0 liter EFI mercs

The first ones in the late 90s, which are refered to as a 300 promax, or 300pm are pretty well know to put out around 290hp stock, however the later 300x motors put out more like 330 HP.

JMARTIN posted 10-12-2007 02:01 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
So, is Larry: Burt, Jackie, or Sally?


blkmtrfan posted 10-12-2007 02:30 PM ET (US)     Profile for blkmtrfan  Send Email to blkmtrfan     
Don't you mean Bandit, Bufford T Justice, or Frog

A little more info about the old Mercury 3.4, there was a version that made well over 300 hp it was called the T-4: jpg

Regading the new optimax 300xs, here is the HP graph: 300xspowergraph2ra.jpg large_optimax300xs.jpg

JMARTIN posted 10-12-2007 02:52 PM ET (US)     Profile for JMARTIN  Send Email to JMARTIN     
What about the stood up groom who could not have sprung from Bufford's loins? What was his name? John
phatwhaler posted 10-12-2007 02:52 PM ET (US)     Profile for phatwhaler  Send Email to phatwhaler     
I'm pretty sure the Snowman just said "Mercy sakes, they said it couldn't be done." A 300 horse outboard that is.

pw out.

L G H posted 10-12-2007 03:33 PM ET (US)     Profile for L G H  Send Email to L G H     
Peter posted 10-12-2007 03:59 PM ET (US)     Profile for Peter  Send Email to Peter     
Since Larry's got us all telling stories ....

I just found a Lake X security camera picture of Larry when he was a young Mercury sales trainee in the 1960s apparently catching him secretly recalibrating the Official Mercury Dynamometer in the HP certification laboratory at Lake X after all the employees went home for the day. See timothy-dynomometer.jpg . Apparently, as the photo reveals, when Larry got done "recalibrating" (wink, wink), the needle on the OMD was showing 30 HP without any motor attached.
Apparently, none of the techs ever noticed the fact that the needle on the OMD didn't rest on zero when its not in use. Oddly, however, when the marketing and sales department asked the Lake X techs to do some comparative dyno testing of Mercury motors and competitive motors, they never let the lab techs run the competitive motors on the OMD. ;)

Once again, in the 1970s, the security cameras at Lake X caught Larry in action after hours "recalibrating" (wink, wink) the new OMD GEN II. See

fourdfish posted 10-12-2007 04:46 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
After reading this thread, It would seem that Larry wished he had not started something he could not finish!
He never quotes any sources for his "facts" except sometimes misquoting the B&B Magazines, and when he gets egg on his face he
falls asleep Zzzzzzzzzzzzzzz! Which is a protective mechanism!
andygere posted 10-12-2007 05:23 PM ET (US)     Profile for andygere  Send Email to andygere     
The 10% rule has allowed the companies to take liberties with the consumer, a really poor situation I think. It does need to be changed by the NMMA, even though it is not in their interest to do so. As buyers we should get close to real HP we are paying for, manufacturing tolerances accounted for, never less. If they want to give us a little more, well that's OK. It's why I buy Mercs. Most are conservatively rated, a company practice for years and years.

Here's how it really works: Random%20Whaler%20Photos/lhg.jpg

fourdfish posted 10-12-2007 05:26 PM ET (US)     Profile for fourdfish  Send Email to fourdfish     
OMG Andy, That was great! That really deserves a CW award!
Tohsgib posted 10-17-2007 11:53 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Junior was Bufford's son's name.

I have a 1980 Merc brochure that has 2 pages dedicated to the 3.4L Merc 300hp. It is NOT in the 1981 catalog. I have actually seen ONE 300 Merc back in the mid 80's on like a 24 Regal or something, never saw I assume they saw limited production.

All the companies had/have non hp designated engines, even Yamaha back in the 80's. It had gold decals but I am drawing a blank as of its name(Special?). Most just referred to it as a 220hp. Many of the other engines like the 150GT were marketed as "hot" engines but they still made 150hp. I think they had Boysen reeds which gave them a better throttle response but not really any more hp.

As far as Merc always having higher Hp engines...anyone ever own a 3cyl 70 or a 2cyl 35/40 back when? Utter dogs compared to the competition. The inline 6's were some bad arse engines though when stacked up against OMC. Then again we all know 6cyls are faster than 4cyls, even today. A 135 V6 will smoke a 140 Looper, no replacement for displacement.

Peter posted 10-17-2007 11:57 AM ET (US)     Profile for Peter  Send Email to Peter     
Nick -- It was called the EXCEL.
Tohsgib posted 10-17-2007 12:47 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Ya Mon!
devildog posted 10-19-2007 04:23 PM ET (US)     Profile for devildog  Send Email to devildog     
"It's over son, they don't even know the Snowman."

"They don't huh? Well I guess it's time we introduce him to the boy. Hold on ya ass, Fred!"

TRAFFICLAWYER posted 10-19-2007 04:29 PM ET (US)     Profile for TRAFFICLAWYER    
I'm gonna get 300 hp when I Repower..............

TWO F150 Yamahas. hehehehhehehhehehehhehhehheheheheh

Looked like a young Don Knotts in the foto.

Contender25 posted 10-19-2007 05:34 PM ET (US)     Profile for Contender25  Send Email to Contender25     
here is a picture of a 1983?? 300hp Merc on the back of a 23 SeaCraft SeaVette both are rather rare. Last I was told the 300 still runs.

blkmtrfan posted 10-19-2007 05:47 PM ET (US)     Profile for blkmtrfan  Send Email to blkmtrfan     

Update on the seacraft:

XStech posted 10-19-2007 07:09 PM ET (US)     Profile for XStech  Send Email to XStech     
7 Manufacturing tolerance
The corrected power at rated speed of any individual marine propulsion engine or propulsion system must not deviate more than ±10% or 0.45kW, whichever is greater, from its declared power, except that for governed engines or systems of more than 100kW [134-HP] the tolerance shall be ±5%.

(End transcription of the ICOMIA 28-83.)

Tohsgib posted 10-22-2007 11:07 AM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Is/was that Seavette sitting in a person's yard in Mystic Islands, NJ? I saw one a couple years ago that looked almost abandoned...very rare beast, engine and boat.
Contender25 posted 10-23-2007 07:36 PM ET (US)     Profile for Contender25  Send Email to Contender25     
yes that boat was probably the one you knew in NJ, it is now in little egg harbor inlet? I do not know jersey too well but thats the boat.
jimh posted 09-19-2008 08:48 AM ET (US)     Profile for jimh  Send Email to jimh     
[This old discussion was revived in order to completely change the topic. Please begin a new discussion if you wish to completely change the topic of an existing discussion. Please do not revive old threads unless there is some compelling reason to do so.]

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