Another 25hp to 35hp thread

[thecadman99]

Well, my old carb was leaking from the primer hose that runs under the carb, and attaches on top of the carb where it meets the intake.
Whoever had installed it last had pinched the tube with the starter and if finally gave out. I thought this was a good excuse to fit the 35hp carb I recently acquired.

This is on a Johnson 25 made in 1992 model j25elens
The carb was listed as a 35 (though it would really be a max 30hp at the prop if I understand the way these motors are rated now).
The 35 carb is older, but I don't know the exact year.

I went through the 35 carb and the seals all seemed to be in good condition.

Let me say that getting the starter off was tough! I had taken the starter of my merc 25 several times and its much simpler. The Johnson required me to use universal joints on my 1/4" drive sockets, and had a very specific disassembly/reassembly order that took me a while to figure out.

After I finally got the carb off, you can see a comparison of the two (yes my foam is deteriorating in my cover)

You can see the different idle mixture screws. Angled on my original carb, and front mounted on the 35.

35 in place

The intake hole on my 25 was the exact size of the 35. I did not have to modify the 25 intake.

I used a smaller piece of tubing for the primer, so no pinching.

Took a minute to get it running, but it seems to idle OK on muffs with a little stuttering. It revs quicker with the new carb.
I can't see the mixture screw for idle doing much. I can screw it all the way in and it still runs. I've just been backing it out about a half turn. Hard to adjust it on muffs.

I hope to take it out today and see how it goes.

 

[crazymanme2]

Can you back your idle screw out so it misses?On my motors if I turn the idle screw all the way in it will quit.
Maybe lil blu will pop in & give his opinion.

 

[Lil' Blue Rude]

Only thing that really stands out to me is it looks like the seal around the idle screw is missing. Might just be the way the picture looks, but there's normally a seal there.

 

[thecadman99]

Yeah, now that you mention it, the screw turns in and out very easily. I thought about wrapping it in some teflon tape.
Is the seal there for for an actual air seal or is it for friction?

Looking at part 17 in the diagram here, I'm assuming its just for friction?
https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1988&hp=35&model=J35RCCE&manufacturer=Johnson&section=Carburetor

 

[Lil' Blue Rude]

Not sure. They fit in tight enough it could serve as both. You might get away with the Teflon tape. Might just be a temporary fix though.

 

[thecadman99]

I just received a carb rebuild kit but haven't had a chance to dig into it yet. I believe it has that slow speed idle seal in it. I'll stick that seal in and see if it changes the idle.

Too bad I jumped the gun and installed the carb, I should have just waited to rebuild it first.....
I guess I might as well take it back off and do it right.

I honestly thought it would be much easier to remove/install. I don't think I could do it in under an hour. Those Johnson engineers must be a bunch of masochists :LOL2:


Can anyone recommend a good page on how to check my timing? Its a 92 25hp.

 

[jasper60103]

...

I honestly thought it would be much easier to remove/install. I don't think I could do it in under an hour. Those Johnson engineers must be a bunch of masochists :LOL2:


...

Yea, I never removed with the starter. What was the most difficult part(s)?

 

[Jim311]

The timing is pretty simple. I think there's a clocking ring with a notch on it. When the little roller for the throttle that rides on the ring starts to lift away from that ring the notch should line up right as it starts to lift off. Verify that but I believe it's the correct procedure.


Your mixture screw when screwed all the way in should stall out the motor so there may be a problem. I believe the starting point for the idle screw is 1.5 turns OUT after you've screwed it all the way in. Likely you will need to unscrew even further but you'll have to fool around with it on the water and make sure it's not only idling but will run into the current well without sneezing or stalling.

 

[thecadman99]

...

I honestly thought it would be much easier to remove/install. I don't think I could do it in under an hour. Those Johnson engineers must be a bunch of masochists :LOL2:


...

Yea, I never removed with the starter. What was the most difficult part(s)?

Going from this diagram: https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1992&hp=25&model=J25ELENS&manufacturer=Johnson&section=Cylinder+%26amp%3B+Crankcase

I'm sure there is a better way to do it, but right from the get go you have to remove two small bolts (48) that capture the shift rod, they have two keepers (55) on either side of the rod and they are easy to drop.

Then there is a single nut right beside the carb (44)(easy) and two bolts on the side (74) easy and (47) difficult- had to use a universal joint on my ratchet.

Then you need to unbolt all the electrical connectors on your starter solenoid. (make sure the battery is disconnected, and take pics first).

THEN you can start to wiggle the starter out the front. Doesn't sound that bad but I had a trying time with it. I would drop a bolt (non magnetic), and spend 20 minutes with a wire trying to dig it back out lol.

 

[thecadman99]

The timing is pretty simple. I think there's a clocking ring with a notch on it. When the little roller for the throttle that rides on the ring starts to lift away from that ring the notch should line up right as it starts to lift off. Verify that but I believe it's the correct procedure.


Your mixture screw when screwed all the way in should stall out the motor so there may be a problem. I believe the starting point for the idle screw is 1.5 turns OUT after you've screwed it all the way in. Likely you will need to unscrew even further but you'll have to fool around with it on the water and make sure it's not only idling but will run into the current well without sneezing or stalling.

Thanks Jim, I'm thinking that the screw may still be a little dirty, and not seating all the way. I didn't want to put too much force on it, but I'm going to spray it with carb cleaner and screw/unscrew it a bunch of times to see if it goes in any more. I also have new seals and the seat I'm going to add to it.

Hopefully I won't have to work 12 hours again tomorrow and will actually get to get on the water before the lake freezes here in Va. (its cooold!)

 

[thecadman99]

Edited part numbers
I'm sure there is a better way to do it, but right from the get go you have to remove two small bolts (sorry thats 34, not 48 as above) that capture the shift rod, they have two keepers (55) on either side of the rod and they are easy to drop.

Then there is a single nut right beside the carb (44)(easy) and two bolts on the side (74) easy and (47) difficult- had to use a universal joint on my ratchet.

Then you need to unbolt all the electrical connectors on your starter solenoid. (make sure the battery is disconnected, and take pics first).

THEN you can start to wiggle the starter out the front. Doesn't sound that bad but I had a trying time with it. I would drop a bolt (non magnetic), and spend 20 minutes with a wire trying to dig it back out lol.

 

[jasper60103]

...

I honestly thought it would be much easier to remove/install. I don't think I could do it in under an hour. Those Johnson engineers must be a bunch of masochists :LOL2:


...

Yea, I never removed with the starter. What was the most difficult part(s)?

Going from this diagram: https://www.marineengine.com/parts/johnson-evinrude-parts.php?year=1992&hp=25&model=J25ELENS&manufacturer=Johnson&section=Cylinder+%26amp%3B+Crankcase

I'm sure there is a better way to do it, but right from the get go you have to remove two small bolts (48) that capture the shift rod, they have two keepers (55) on either side of the rod and they are easy to drop.

Then there is a single nut right beside the carb (44)(easy) and two bolts on the side (74) easy and (47) difficult- had to use a universal joint on my ratchet.

Then you need to unbolt all the electrical connectors on your starter solenoid. (make sure the battery is disconnected, and take pics first).

THEN you can start to wiggle the starter out the front. Doesn't sound that bad but I had a trying time with it. I would drop a bolt (non magnetic), and spend 20 minutes with a wire trying to dig it back out lol.

thecadman99,
thanks for the detailed explanation. Yea, I can see how it can be a pain. I bet you can do it blind folded now though . Sounds like the throttle lever (#31) doesn't have to be completely removed to wiggle the starter out?
Thanks again for the info, I may have to service my carb over the winter.
-jasper

edit: I noted your corrections above. Thanks.

 

[thecadman99]

thecadman99,
thanks for the detailed explanation. Yea, I can see how it can be a pain. I bet you can do it blind folded now though . Sounds like the throttle lever (#31) doesn't have to be completely removed to wiggle the starter out?
Thanks again for the info, I may have to service my carb over the winter.
-jasper

edit: I noted your corrections above. Thanks.

You're welcome
I'm not sure about the throttle, my motor is a cable steer... The fuel hoses were in the way of the starter coming out, but they weren't too hard to work around.

 

[Charger25]

Have you run it and tested it out yet? Just wondering if there was a big difference.

 

[Jim311]

The timing is pretty simple. I think there's a clocking ring with a notch on it. When the little roller for the throttle that rides on the ring starts to lift away from that ring the notch should line up right as it starts to lift off. Verify that but I believe it's the correct procedure.


Your mixture screw when screwed all the way in should stall out the motor so there may be a problem. I believe the starting point for the idle screw is 1.5 turns OUT after you've screwed it all the way in. Likely you will need to unscrew even further but you'll have to fool around with it on the water and make sure it's not only idling but will run into the current well without sneezing or stalling.

Thanks Jim, I'm thinking that the screw may still be a little dirty, and not seating all the way. I didn't want to put too much force on it, but I'm going to spray it with carb cleaner and screw/unscrew it a bunch of times to see if it goes in any more. I also have new seals and the seat I'm going to add to it.

Hopefully I won't have to work 12 hours again tomorrow and will actually get to get on the water before the lake freezes here in Va. (its cooold!)

If you are still getting fuel despite the needle being screwed all the way in, it's likely that your needle or seat are worn/damaged and need replacing.

 

[thecadman99]

I added the seal that Lil blue rude mentioned (around the low speed mixture) and finally go to take the boat out.
I was a bit disappointed (expecting a huge difference) but the boat started and idled well and top speed went from 24 max to 27 max with myself and the wife on the boat + fishing gear. It didn't hold 27 all the time though, that was just for a small section.
The average was probably closer to 25 (up from a 23mph average), not exactly a huge leap. The cheap tach I put on kept jumping all over but averaged about 5400 rpm, up 200 rpm from my other carb. This was with a Solas 10X13 prop.

I will say that it "felt" (very subjective that) like I had a lot more takeoff, and got on plane easier.
I took myself, my wife, her sister, and two small kids out and still planed well averaging 24mph.

I need to check the timing on the motor (still learning about timing) and I really should rebuild the larger carb but all in all I would say that you do get a small boost from putting a larger bore carb on a 92 Johnson 25hp. Just don't expect miracles.

 

[jasper60103]

I added the seal that Lil blue rude mentioned (around the low speed mixture) and finally go to take the boat out.
I was a bit disappointed (expecting a huge difference) but the boat started and idled well and top speed went from 24 max to 27 max with myself and the wife on the boat + fishing gear. It didn't hold 27 all the time though, that was just for a small section.
The average was probably closer to 25 (up from a 23mph average), not exactly a huge leap. The cheap tach I put on kept jumping all over but averaged about 5400 rpm, up 200 rpm from my other carb. This was with a Solas 10X13 prop.

I will say that it "felt" (very subjective that) like I had a lot more takeoff, and got on plane easier.
I took myself, my wife, her sister, and two small kids out and still planed well averaging 24mph.

I need to check the timing on the motor (still learning about timing) and I really should rebuild the larger carb but all in all I would say that you do get a small boost from putting a larger bore carb on a 92 Johnson 25hp. Just don't expect miracles.

thecadman99,
thanks for the update. Sorry you didn't get the performance you were expecting.
I admit I never done this mod. Hopefully johny25 will chime in, or someone else with knowledge on this.

-jasper

 

[shawnfish]

I added the seal that Lil blue rude mentioned (around the low speed mixture) and finally go to take the boat out.
I was a bit disappointed (expecting a huge difference) but the boat started and idled well and top speed went from 24 max to 27 max with myself and the wife on the boat + fishing gear. It didn't hold 27 all the time though, that was just for a small section.
The average was probably closer to 25 (up from a 23mph average), not exactly a huge leap. The cheap tach I put on kept jumping all over but averaged about 5400 rpm, up 200 rpm from my other carb. This was with a Solas 10X13 prop.

I will say that it "felt" (very subjective that) like I had a lot more takeoff, and got on plane easier.
I took myself, my wife, her sister, and two small kids out and still planed well averaging 24mph.

I need to check the timing on the motor (still learning about timing) and I really should rebuild the larger carb but all in all I would say that you do get a small boost from putting a larger bore carb on a 92 Johnson 25hp. Just don't expect miracles.

you should see quite a difference, when I put the 35 carb on my 25 it made a big difference. try a different prop, you should be close to or at 6000 rpm's WOT, don't worry about it cuz 25 and 35 powerheads are the same and the added rpm's wont hurt nothing and your lower unit can handle it. I gained around 8-9 mph with mine and its very noticeable... its all in the right rpm's and the right prop if you want the added hp and performance... I ran my 25 carb at 5500 rpm's and the 35 is at 5900 or a little more to get more from my 25 motor with the 35 carb

 

[shawnfish]

fiddle with diff props if that's an option for you and also make sure your throttle and cam are in sync.... very important