1980's Johnson/Evinrude 20/25hp conversion to 30hp with pics

[user 12972]

What a great thread! I'm hoping it will serve me too. I've got an '84 Johnson 30 remote (so 25 at prop?) I'd like to get just a bit more out of. It's on a Grumman 1448 that as a kid my dad and I spent HOURS fishing in, and believe it or not I used to ski, kneeboarding, and tube behind. I know a 30hp is a slightly larger rating for the boat already but after I mod it up (floors, seats, etc) I think I'll need just a little more oomph to pull my kids, and ok maybe myself. :LOL2: Short of doing the research for parts, is it worth it in your opinion? Could I gain just 5 more? Man, what a difference that would make. And just so you know, I've just recently rebuilt the transom to stronger dimensions, so I think the boat will be able to handle the HP. Thanks for your comments.

 

[user 12972]

After doing a fair amount of part number cross referencing, it appears the 30 and 35 hp motors in 1984 used identical intakes, reeds, carbs, low speed needles, and high speed orifices. Even identical pistons, rods, and cranks. So how did they manage to get another 5 hp from one to the other? I noticed on boats.net that two different high speed orifices were used in both motors, a 61D and a 63D but it didn't clarify where/when they were used. Part numbers are 0319907 and 0328544 respectively. I can only assume one is slightly larger than the other, is it safe to assume the 63 would be larger, or do they follow drill bit sizes and therefore be the smaller? I'm gonna have to pull mine out and see what's installed.

 

[Country Dave]

Hey man very cool thread,

Definitely good info for anyone who want to get a few more ponies out of there OB........................ =D>

 

[jasper60103]

Natemeins » Yesterday, 3:51 pm[/url]"]After doing a fair amount of part number cross referencing, it appears the 30 and 35 hp motors in 1984 used identical intakes, reeds, carbs, low speed needles, and high speed orifices. Even identical pistons, rods, and cranks. So how did they manage to get another 5 hp from one to the other? I noticed on boats.net that two different high speed orifices were used in both motors, a 61D and a 63D but it didn't clarify where/when they were used. Part numbers are 0319907 and 0328544 respectively. I can only assume one is slightly larger than the other, is it safe to assume the 63 would be larger, or do they follow drill bit sizes and therefore be the smaller? I'm gonna have to pull mine out and see what's installed.

61D and 63D orifice plugs are used on the 30 and 35 hp respectively. See marine engine...

https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1984&hp=30&model=J30ECRR&manufacturer=Johnson&section=Carburetor

Good luck.

jasper

 

[user 12972]

Thanks Jasper. I did some more research on the BRP website as well and from what I can tell the carb, high speed orifice, low speed needle, intake, reeds, and reed stops were slightly different, as they all had different part numbers. As availability of these parts were lost part distributors superceded to the same part that was used in the 87 30hp and sold them to the 84-88 jonnyrudes 20-35hp. So I'm faced with trying the cheap way and try a 63D high speed orifice and hope for the best (I have a 61D in it now) or I'll have to replace the manifold, reeds, reed stops, and gaskets. (They actually sell a "leaf" plate assembly which comes with most of the above parts for a single decent price, but the intake manifold is between $114 and $142 new. May not be worth trying to get 5 hp with all that. It would be nice to have a true 30hp motor though, as opposed to 25hp at the prop.

 

[RStewart]

Thanks for all this info. It will be very helpful. I can't figure something out though. I have a 1999 9.9 Johnson. I was trying to see if I could increase it to a 15 hp motor. My model # is J10REER & I crossed it with a J15REEA, closest model number to mine. I checked carb, intake, crankcase, reed plate, exhaust, pistons, & gear case & both engines have the same part numbers. How does the 15 make more power? What can I do to get more power from the 9.9? It is on a 1968 Rich line 14 ft aluminum semi v & it will not plane out. I do know one of my issues is I have a long shaft motor on a short transom. I would love to get a 25 hp motor & do this mod to it, but for now I'm stuck with the 9.9.

 

[RStewart]

Ok, so after close examination I've learned that I'm a goob. When I looked up offset numbers fit both motors, it gives both carb numbers, fit the 9.9 & the 15. I didn't realize this so the carbs are not the same. Everything else software to be the same so I need to find a carb from a 15 & I'm good. I may just buy a new one.

Now I would like to know what years would interchange with mine? Or how I can find out what years? Thanks.

 

[Johny25]

My guess would be any 15hp carb from 94' to 2001 but you will have to research it a little more. In 94' they went to the 15.6ci block and in 2002 they started making the 4 strokes I believe with the 2 strokes. But I guess off the top of my head would be that year range

 

[RStewart]

Thanks Johny25.

 

[bigredxlt]

If the 84 johnson that were labeled at 30 are really only putting out 25 at the prop does the same go for the 84 johnsons labeled at 25? are they really only putting out 20?

 

[Johny25]

1984 they did not make a 30hp......was a 35hp. 1985 was first year of the prop rated HP and the 35 became the 30hp. So yes prior to 1985 the engines were not putting out the rated HP at the prop. They were rated at the crank before 85'

I believe they would lose about 10-15% HP from the crank to the prop so if you calculate that out it would be 2.5 to 3.7hp difference on a pre 1985 25hp engines......so maybe 21.5 to 22.5hp at the prop for a pre 85 25hp....hope this helps

 

[dkonrai]

i had a older 72 johnson 20 hp. i stuck a 25 hp carb on it and it flew. it was on a 14 foot duroboat and at wot it was scary fast. sold it to a guy who is still running the motor. i didnt have a gps, but, it planed in seconds but would chine walk at wot.

https://www.youtube.com/watch?v=E5_RQaHvx4Q

i now have a 80 johnson 25, that needed a lot of work. i got it back together and am going to swap out the intake and carb (if i can find a set cheap) . motor seems to have way more power than the older 72 but still has the little split case lower unit. im thinking the lower should hold up as the 50's motors (30hp) had the same style lowers.

here she is running. i have since installed a lanyard style kill switch (missing in the vid, thats the loose wire)

https://www.youtube.com/watch?v=sySIsymJeSQ

thanks johny for inspiring us with your great thread,
dino

 

[Johny25]

Nice video of the old 20 screaming around......although my head is now kinked lol. The 72' you had was the small 22ci block which was used on the 20 and 25hp's up until 77' I believe when the bigger 31.8ci block began being used. Those old 22ci motors were very light and had a great power to weight ratio......think that motor you had was likely less than 85lbs as opposed to the 80' you have that weighs 30+ pounds more I would guess

 

[dkonrai]

Johny25 » 41 minutes ago[/url]"]Nice video of the old 20 screaming around......although my head is now kinked lol. The 72' you had was the small 22ci block which was used on the 20 and 25hp's up until 77' I believe when the bigger 31.8ci block began being used. Those old 22ci motors were very light and had a great power to weight ratio......think that motor you had was likely less than 85lbs as opposed to the 80' you have that weighs 30+ pounds more I would guess

johny,
sorry about that kink in your neck. it was so hard to vid and drive at the same time lol. i couldnt wot only in short little spurts. the torque steer and chine walk made my but pucker a bit. yes great power to weight ration. it was a little heavier than my 9.9/15's. trolled nice too (surprising).
i have a 30 hanging off the back of my 16 foot bayrunner, she seems a little under powered
dino

 

[ccm]

Hey RStewart I think the reason your boat isn't plaining out is because of the long shaft. I have a 1961 Sea King PDUT built by Arkansas Traveler(same as DUT model) I have a 4hp Tohatsu 4stroke tiller model and if I move to the second bench seat the boat will plain out nicely. I have just bought a Stingray Junior Hydrofoil to see if it will plain with me at the back bench. If I were you I might try a jack plait to get the cavitation plate to the same level as the bottom of the hull. And as far as turning my motor into a 6hp it will happen when my warranty expires. (two years to go ) Good luck to you in converting your motor into a 15hp.

 

[thill]

I have an Evinrude 25 HP engine, E25RERC, a 1994. It pushes the boat great, but the hull was originally rated for up to 60 HP, and it is no where near "scary fast".

Any idea of whether it's possible to upgrade the performance of a 1994 engine?

Thanks.

-Tony

 

[Boat2fast]

Your engine is a shortshaft? The boat is rated for 60? Either the boat is an early model or the engine has been converted to longshaft. If the boat is a fairly good sized hull, I would start looking for a 40-50hp Johnson Evinrude. This will be a very good upgrade. Take your time and look for a low hours unit made 1982-1988. Late model etecs are good if you can afford 'em.

opinions, 2c

 

[thill]

The boat is a 1957 Crestliner Viking 710 that has been gutted out, the front hood cut back, and a large front deck added. The motor is a 1994 Evinrude 25 short shaft.


Here is the original brochure- mine is the " 710- decked," the top right picture, pulling the waterskiiers and the third floor plan from the left. The one with the windshield and only two bunks:

https://retrocrestliner.com/images/1957catalog p9and10.jpg


Here is a picture of my boat currently:
https://retrocrestliner.com/phpBB3/download/file.php?id=745


I could re-do the transom up to a 20" and use a 40 HP that I already have, but I don't want to add all that extra weight to the back, and the remote controls, if I can help it. That 40 weighs TWICE what this 25 does. I like the additional seaworthiness the lighter rear end gives me.

The 25 pushes the boat well- about 25 MPH- but if I could get a little more power without gaining weight, that would be ideal. Let me know. Thanks.

-TH

 

[Boat2fast]

Nice hull. Nice build-up. Crestliners are well made boats. I had a 1964 welded 14ft rated for 50hp.

Check out some videos. This is a shortshaft tiller engine. This Johnson 40 was a longshaft when I bought it. It has been converted to shortshaft. Shortshaft boats that take big engines are getting scarce.

(Use guest password: twist'er)

https://www.dropshots.com/boat2fast#albums/40hp reconstructed

*********

 

[thill]

That 40 runs nicely! What is your top speed? Looked like you were backing off a bit in the vid.

I'm sure my 40 would be fast, but I tend to go out in heavy seas, and the lighter the motor, the higher the transom floats, and the safer and seaworthy she will be. I've seen the back of a small boat go ker-plunk with too much weight in the back, and it's not a pretty sight.

That's why I'm trying to figure out whether a 30 or 35 carb will do me any good... If not, I think I'm sticking with this engine. It does 23-25 as currently rigged, which I'm happy with. I think I need to go down a prop size, though... not sure yet.

Thanks.

-TH