Old outboards rated differently?

[BJM]

I pulled up to my local launch and there was a gut with a late 80's Bayliner Capri that was incredibly beat up. My neighbor has the same boat with a Force 85hp on it. This guy has an ancient 140 hp Johnson. He tells me the ditched the 85 when it died and that it performed just as well as the 140 since outboards used to be rated at the crank and new ones are rated at the prop shaft.<br /><br />First of all, is this true? Cars switched from SAE Gross to SAE Net in 1973, but boats don't have much of a drivetrain between the crank and the prop, just a couple of gears.<br /><br />I figured his old 140 is just worn out.

 

[sho305]

Re: Old outboards rated differently?

I guess in the 70's most makers changed ratings, and Merc waited until the early 80s. Some older motors are rated strange though. Saw an old Seahorse 7.5 blow away a late 80s 9.9 once. Search around and you can find out just when. I have an old '73 Merc 150 and I figure it for a 125hp. Merc made the same inline 6 from 90 to 150hp so what gives? It runs 54mph on a 17'.<br /><br />Newer motors tend to have more ci displacement as well. I will be running my '83 Force 85 soon, and it is supposed to do close to 40 on a 16' Bayliner. Had an old Merc 80hp on a small 17' that ran 37mph or so.

 

[what200]

Re: Old outboards rated differently?

Most engine mftrs switched to prop shaft HP around mid 80's. On mercurys it depended on the model, but I know the inline6 became prop rated in 85. Suzuki started in early 80's. I don't think Forces were ever rated at the prop.<br />I have heard the gearcase usually amounts to a 10-15% loss. Mercury's 140 became a 115. I'm assuming the same for OMC's 140. But in any case, if a 140 crossflow johnson can't hang with a 3 cyl force something is wrong with it.

 

[sho305]

Re: Old outboards rated differently?

I agree, those old Johnsons run good. I had a early 80s 85hp v-4 Johnson blow the doors off my mid 70s 80hp Merc. I had a little narrow 17, and he had a big 18' trihull deckboat! Must have not been in a very good state of tune.

 

[Dhadley]

Re: Old outboards rated differently?

Set up is everything. I won a couple of drag races in the V6 class a few years ago. With a V4.<br /><br />Good luck!

 

[ivar]

Re: Old outboards rated differently?

Or maybe it was propped totally wrong , with sluggish acceleration and poor top end as a result?<br /><br />I also read in some earlier posts that the 140 v-4's had less holeshot than the 90hp v-4 , because it was in a higher state of tune and needed more rpms to breathe and make HP.