How are outboards rated for horsepower?

[Silly Seville]

Hi Gents,

Regarding my newest toy, '69 Johnson 85 V4...does anyone know how the horsepower rating was determined?
Crankshaft or propshaft?
I'm interested in a 70's Checkmate or Carlson speedboat, and they are both rated for a maximum of 70 hp.
Will my little 85 overwhelm the transom of a 15-16 foot closed bow mini go-fast?
I've always wondered how boat manufacturers decide on hp ratings when they aren't outfitting their particular craft with a powertrain. I have a sneaking suspicion that a boat rated for "X" horsepower, can really take more. By a wide margin in fact. Can anybody confirm or refute that notion?

Thanks!

 

[Fleetwin]

Re: How are outboards rated for horsepower?

Crankshaft until 1983.

The US Coast Guard has formulas for determining max. HP. Some of the ratings also to into account-weight.

 

[Frank Acampora]

Re: How are outboards rated for horsepower?



Horsepower rating was standardized for all outboard engines in the early 1980s to be measured at the prop.

While your Johnson was probably rated at the crank, It makes no difference to the law enforcement officers: The engine is an 85 and the boat is overpowered.

Your question has been beaten to death in the past on the forum. The answer is still the same: The engine IS what the decals AND the model plate state. AND, LEO are not stupid. Simply changing the decals will not fool them. Oh, you may "get away" with it and never be stopped but then again, you may be stopped and issued a citation.

Now, here are two hulls that were rated for modest horsepower. The tunnel hull was rated for class racing with a Mercury 25. It is now powered with a 50 or 60. The other one was probably rated for around 35-40 and it was powered with a 125 after some severe modifications. Notice how low the little blue tunnel sits at rest with the weight of the 60 on the back.

And yes, you are correct: The exact same hull in outboard and I/O version is rated differently. I/O has no horsepower rating and you can stuff as much as you want into it. Similarly, you can power a jet ski with as much as you want.

 

[metriccrescentwrench]

Re: How are outboards rated for horsepower?

I'm interested in a 70's Checkmate or Carlson speedboat, and they are both rated for a maximum of 70 hp.
Will my little 85 overwhelm the transom of a 15-16 foot closed bow mini go-fast?

What Checkmate are you looking at? Something doesn't add up as far as being 15 or 16 ft and only rated for 70 HP. For instance, I just looked at the specs for a 1972 Checkmate MX-15 (15 ft) and it's rated for 140HP.

And if you care to look further, about midway down this page are links to all the Checkmate brochures all the way back to 1967. They list specs (including max HP if applicable) for each model.

Checkmate Community Photo Gallery - Checkmate Community Forums Gallery

 

[Silly Seville]

Re: How are outboards rated for horsepower?

What Checkmate are you looking at? Something doesn't add up as far as being 15 or 16 ft and only rated for 70 HP. For instance, I just looked at the specs for a 1972 Checkmate MX-15 (15 ft) and it's rated for 140HP.

You are absolutely correct. I have looked at and called about so many boats this past week that I'm getting my names and numbers mixed up. I called about a Checkmate Predictor that had a 70 horse on it that the owner was in the process of removing. I also looked at a few antique Sea Rays that all were in the 50-70 horse range...so that number is stuck in my head. Now that I see the Checkmates can take way more engine, I will probably avoid them since my 85 would be WAY underpowered and leave me looking silly at the ramp! :lol:

BTW, when I bought this engine I thought it was a 100. I was disappointed when I finally figured out it wasn't. Obviously, someone years ago thought it would be cute to put a 100 horse cowling on it. :facepalm:

 

[Frank Acampora]

Re: How are outboards rated for horsepower?

The four cylinder OMC started out as the "Fat 50" --a vee 4 with a smaller bore than your engine. Through the years, the bore and horsepower was increased.

Since later model OMC engines up to 120 were all the same block, bore, and stroke, your engine may have the 3.5 inch bore and you may be able to upgrade your 85 to a higher horsepower. It would involve a bit of work though: You would need to do some port work, install a "bubble back" with tuned downtubes, and different carbs. Upgrading the ignition would help too.

I'm not too familiar with OMC modifications but you should be able to get really good info on the OMC forum.

 

[Silly Seville]

Re: How are outboards rated for horsepower?

Thank you Frank...now I'm going to ask an additional newbie question. Why am I seeing the name OMC referred to? Did OMC buy out Johnson? I guess I need to do more research. Over on the Mercruiser forums, the word OMC is like a death sentence to anyone who utters it. If OMC is hated so much by the I/O crowd, what is it doing attached to a quality name like Johnson? And btw, can I assume that Johnson is actually no longer in existence by that name ,but instead Evinrude? I have a lot to learn apparently! :facepalm:

 

[Silly Seville]

Re: How are outboards rated for horsepower?

Here are the boats I'm now interested in. Not the actual boats of course, but this model. According to online spec's, these boats were best pushed by 70-90 ponies. I think my 85 would be comfortable with that duty. I got this engine at an auction for what is probably considered a steal considering how much the damn ignition amplifier alone is worth! Now I just want a cool little speedmeister to mount it on. I get tired of dragging the heavy Sundancer around in the summer.

 

[Scott Danforth]

Re: How are outboards rated for horsepower?

Thank you Frank...now I'm going to ask an additional newbie question. Why am I seeing the name OMC referred to? Did OMC buy out Johnson? I guess I need to do more research. Over on the Mercruiser forums, the word OMC is like a death sentence to anyone who utters it. If OMC is hated so much by the I/O crowd, what is it doing attached to a quality name like Johnson? And btw, can I assume that Johnson is actually no longer in existence by that name ,but instead Evinrude? I have a lot to learn apparently! :facepalm:

OMC = Outboard Marine Corp. that is the company that made brands like Johnson and Evinrude, etc. the company went bankrupt, and the names Johnson and Evinrude were purchased by BRP (Bombardier Recreational Products). The same people who own Can Am, SeaDoo, SkiDoo, etc.

 

[Silly Seville]

Re: How are outboards rated for horsepower?

Ah ha! So that's why I see folks calling their engines Johnnyrudes! I gather Johnson and Evinrude were like Chevy/GMC...essentially the same product, manufactured by the same company, but marketed differently to attract more buyers? Not to hijack my own thread...if that's possible; but does the electric shift outboard I have share the same design flaw that the OMC Stringer outdrives are known and hated for? The purchase of this outboard has been quite an education. I appreciate everyone's input!

 

[Vintin]

Re: How are outboards rated for horsepower?

Evinrude bought Johnson I believe it was in 1935. "A perfect little gold mine" to quote Steven Briggs speaking to Ralph Evinrude.

Thank you Frank...now I'm going to ask an additional newbie question. Why am I seeing the name OMC referred to? Did OMC buy out Johnson? I guess I need to do more research. Over on the Mercruiser forums, the word OMC is like a death sentence to anyone who utters it. If OMC is hated so much by the I/O crowd, what is it doing attached to a quality name like Johnson? And btw, can I assume that Johnson is actually no longer in existence by that name ,but instead Evinrude? I have a lot to learn apparently! :facepalm:

 

[Chris1956]

Re: How are outboards rated for horsepower?

I do not think the "Stringer" sterndrives and Electric shift OBs were hated for the same reason. They were both hated for different things. To be clear, Johnnyrudes were good OBs. The electric shift was not a great idea, but lots of them worked OK.

Frank was discussing making your motor into a 140HP version. That would work on those boats. A v6 motor would weigh them down. Of course they would look 'da bomb' with a Merc Tower on them......

 

[metriccrescentwrench]

Re: How are outboards rated for horsepower?

I got this engine at an auction for what is probably considered a steal considering how much the damn ignition amplifier alone is worth!.....

Here's another thought..... I'd be hesitant to hang an old electric shift engine on a boat since they're difficult to find parts for. Since you got yours for cheap anyways, maybe consider parting the engine out at a healthy profit and combining the proceeds from that with what you were planning on putting into a boat.

 

[Frank Acampora]

Re: How are outboards rated for horsepower?



The boats you are looking at are a Glastron GT150. This is the "James Bond" boat. It is a very desirable hull that does hold its value and can actually appreciate. It is rated for a 90, but in the movie "Live and Let Die" it was powered with a 135 OMC.

If you can find one, buy it! Mine was 1000 bucks in its as-is condition and I did not even try to haggle price.

Mine will eventually be restored and powered with a 140--but I won't make the jump LOL

The reason the Merc guys don't like OMC is because of the very old joke based on Mercury advertising: Take a mercury if you want to get there. Take an OMC if you want to get back. Take a Sears and row back.

AND by the way: The Glastron hulls look best with Chrysler engines as shown in the first two photos..

 

[Scott Danforth]

Re: How are outboards rated for horsepower?

i thought it was the other way around and OMC guys didnt like Merc guys because Carl Kiekhaefer originally worked at Evenrude, then ultimately started making motors and rated his engines at 3/4 throttle vs the enemy's WOT because he believed that there should be some reserve.

 

[Chris1956]

Re: How are outboards rated for horsepower?

Frank, There are no Whaletails on performance boats. Hang a Merc TOP on that thing and you won't need the Whaletail. Gee hard to get past the orange. How about a fresh paint job? Most any color goes with Phantom Black. Chrysler's don't go with Glastrons, IMHO.

 

[Fleetwin]

Re: How are outboards rated for horsepower?

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The boats you are looking at are a Glastron GT150. This is the "James Bond" boat. It is a very desirable hull that does hold its value and can actually appreciate. It is rated for a 90, but in the movie "Live and Let Die" it was powered with a 135 OMC.

If you can find one, buy it! Mine was 1000 bucks in its as-is condition and I did not even try to haggle price.

Mine will eventually be restored and powered with a 140--but I won't make the jump LOL

The reason the Merc guys don't like OMC is because of the very old joke based on Mercury advertising: Take a mercury if you want to get there. Take an OMC if you want to get back. Take a Sears and row back.

AND by the way: The Glastron hulls look best with Chrysler engines as shown in the first two photos..

That is indeed the "Live and Let Die" movie boat. They wrecked almost 20 of them making that famous jump.

Yes, they were over-powered by Evinrude 135's.

The nice thing about the (OMC) John/Rude "crossflow V-4's" is that they look IDENTICAL other than the numbers on the cowl and ID plate. The "crossflows" had many HP ratings, throughout the years: 50, 60, 75, 85, 88, 90, 100, 112, 115, 125, 135. I may have missed a few.

The early ones were based on the 96.9 CID block. (some early 50's and 60's may have been smaller) The later ones based on the similar block punched out to 99.6 CID.

The later versions are easy to identify in the higher HP versions. They all had "bubble back" exhaust covers (between the V on the engine). Those were, typically, the 100 HP and up.

The late 60's through 1972 had the electric shift lower unit. While somewhat troublesome, a good working one does just fine.

The 1973 and up versions disbanded the electric shift and went with a hydraulically assisted shift or a straight lower unit shift.

The OMC V-4's (crossflow) are a bulletproof engine but they are extremely fuel thirsty.

Nothing, on the water, sounds as good as an OMC V-4 at Wide Open Throttle.

 

[metriccrescentwrench]

Re: How are outboards rated for horsepower?

Nothing, on the water, sounds as good as an OMC V-4 at Wide Open Throttle.

Yep..... an OMC V-6 at full tilt boogie!

 

[Fleetwin]

Re: How are outboards rated for horsepower?

Yep..... an OMC V-6 at full tilt boogie!

Baahhhh! The V-6's sound like they have a spark plug wire off. Kind of like a Subaru WRX.:facepalm:

 

[Frank Acampora]

Re: How are outboards rated for horsepower?

Chris: look closely at the photos again. That is a 65 HP Johnson 3 cylinder looper with a whale tail. It is already off the boat and sold. The boat is now sitting upside-down in preparation for sanding the bottom and re gel coating. This is because the O.P. did a crappy job on it.

Orange IS the color of the jump boat and I still maintain that my Chrysler 140 will go on it. It will look WAY better than the black thing you would put on it and will probably get me up past 60.