1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

[Thornes1]

Does anyone know what the WOT RPM is for a 1985 20hp AND a 25hp Evinrude Outboard Short Shaft.
Please only respond if your sure,, no guessing please..

 

[F_R]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

I'm sitting here looking at the specifications chart. Is that sure enough for you? They are both rated at 5000 RPM, and full throttle operating range is 4500-5500 RPM. Now you are probably asking what is the difference. The 25 has more power, therefor able to turn the same RPM with a heavier load or bigger boat. If you were to compare the two on the same boat/load, the 25 probably would be able to swing a slightly steeper prop and be a tad faster.

EDIT: In fact, the 20hp was shipped with a 10 1/2 X 11 prop and the 25 was shipped with a 10 X 13 prop

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

Perfect thank you, you answered my next questions without even asking.
Last fall after a ton of research I determined that my motor was easily converted from a 20 to a 25. I did the mod after I pulled it from the water for the season without measuring any baselines. I in fact have the 10.5 x 11 on the motor right now, and now that its a 25 I knew I would have to re-prop. Providing the as shipped prop for the 25 has saved me a bunch of time and frustration. Opening day is just a few days away,,,
Thanks from Georgian Bay Ontario!!

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

hey thornes1, i am doing the mod on my 92' johnson 20 but changing it to a 30 by doing the intake manifold also,now after hours of searching and poking around i was able to find a couple racing intakes that give 1 more hp and 1 mph, if you have the thru hub exhaust its a 30 if its a above prop exhaust its a 35 think after 86' they rated them at the prop

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

Well I don't think I'm ready for race parts just yet,, we will see if my mod worked first. This is what I'm aware of right now, for my motor ;
20 to 25 - open intake manifold to match carb diameter
25-30 you need to upgrade the carb
From here to 40 requires a new transom mount, carb jet and intake manifold. Other than that all the other parts are identicle. Every mod required propeller pitch change too,,, before I reinstalled the intake I polished it to a mirror surface finish,, hope to get a bit more from that, if not at least I know it's shiny on the inside
I think there were only a few years that this was possible so be sure to cross reference all parts lists. The new 100+ hp etech a are the same too just programmed differently from what I hear as well,, only a few more days till pike and walleye season!!! Yea
If anyone is interested I can post some pictures on the weekend just ask
Bfn

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

i wouldnt mind seeing the polished intake,as far as it being a race intake its used for racing but a stock part off military motors -thats really hard to find ,
your correct on the larger carb to make it to a 30, 25 has 1 3/8'' carb inlet the 30 has 1.5'', not sure about a 40? think that would be stretch those are 3 cyl?? , looking into a race prop to finish off for a couple hundred and make her go 40+ that would rule

 

[Willyclay]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

Lots of info in the thread below:

http://forums.iboats.com/johnson-evinrude-outboards/converting-20-hp-johnson-35-hp-274566.html

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

ive been trying to add photos with no success

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

is that the intake you put on?? the inlet looks kinda small should be same as gasket

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

I bored it out to the same diameter as the carb
was 19 mm
is now 32mm

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

lol holy crap!! what did you use to polish that thang looks damn good

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

Keep in mind im using the carb from the 20 not the 30 hp

 

[Thornes1]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

dremel type tool with the round cotton/felt disc.. eagle one chrome polish,,, shhh don't tell anyone.

 

[waterfowler15]

Re: 1985 Evinrude 20 hp WOT and 25 hp WOT RPM?

wd-40 and air compressor working my way down,put a plastic bag over the carb before hand

 

[bamaboat'n]

How did it run, and how noticeable was the performance increase as a result of the modifications? I have a 1989 Evenrude 20 that I am considering making the same mod too.