Big Twin 25hp 1954?

[aa9ep]

Hi there,New guy here with a couple of questions about my evinrude 25 big twin, I think it is a 1954 Serial # 25012-72809 would like to know exact year if possible. I bought it about 30 years ago as a box motor (all torn apart). It runs full speed great but idles a little ruff,not good for slow trolling.Yes I have tried adjusting the low speed needle valve. I've cleaned the carb. with carb cleaner and blowed out with high presure air and I think I got all those little holes cleared. New coils,plugs but idles the same, is this normal for these big twins ? Could you also tell me the gas mixture ? The guy I got it from said 50:1. I have also seen on these forums 24.1 and 25.1 !!
Thankfull for any help

 

[samo_ott]

Re: Big Twin 25hp 1954?

It is a '53-'54 model. I have the Johnson '54 25hp. Pretty much the same engine. The mix is 24:1. Don't go 50:1 as that's too little oil.

Rough idling could be many things. You have eliminated most of then by rebuilding the carb. Maybe the armature plate is loose? Did it seem tight when you were working on it? Mind you, even at the best of times that big 25 is not a smooth idler.

 

[jbjennings]

Re: Big Twin 25hp 1954?

I would check compression, and if it's not above 115psi, it probably will never idle all that smoothly. I have a '53 johnson 25hp and a '54 evinrude bigtwin also. I had a powerhead that had about 115psi on it and it idled decent but not great, the 120psi powerhead that's on it now idles noticeably better using the same carb and ignition (only difference was the powerhead itself). I remember WBeaton saying that you need to adjust the high speed first, and then the low speed, in order to get it just right. I found that to be good advice as usual. if you don't have good packing around the slow and fast idle needles, it won't idle good either.
Good luck,
JBJ

 

[aa9ep]

Re: Big Twin 25hp 1954?

Hi Steve
Thank you for the info. I will check the armature plate again but it was tight when I had it apart before. thank you for the gas mixture.I have to put a new water pump in it. No big deal there, have did this before. (lol) This was my first and only outboard and really has been a great motor. Would like to get the paint code #s because it has never been repainted and I think it would really look sharp painted.
Again Thank You
Dale from Wis.

 

[jbjennings]

Re: Big Twin 25hp 1954?

To get the RIGHT color there's really no place better than nymarin.ca, but it ain't cheap! good paint, though! Far superior to regular spray paint. If you do repaint it, you'd better pick a day with low humidity and be sure to use self-etching primer on it, especially the lower unit. If your motor still has a lot of paint or primer on it, try not to sand down to the bare metal.
JBJ

 

[aa9ep]

Re: Big Twin 25hp 1954?

Thank You JBJ for your help also, Alot of good info. That looks just like my motor but with a nice paint job. What would you use for needle packing? I will try to check the compression this weekend, hopefully it will be good.
Thank you JBJ
Dale from Wis.

 

[wbeaton]

Re: Big Twin 25hp 1954?

Your motor was built in 1954.

Good advice from Steve and Jason as usual. I had a 1953 with 100 psi that idled ok. You can see it on You Tube.

http://www.youtube.com/watch?v=HxluXSzaqPA

I find those carbs can be a bit particular.