Evinrude 25hp Big Twin Model 25018 “The Evil One”

[olcah]

I would definitely change both upper and lower crank seals. But- my experience with 1954 and 1956 big twins is is that if you run a lot of gas (say 45 + gallons) through these motors, inevitably the top seal (either type) leaks somewhat and usually gets fuel oil mix beneath the magneto, about as shown in your photo. Even with new seals and new crankshaft. The key is whether the fuel and oil gets to the points on top of the magneto plate and shorts the points. Then one cleans the mag plate and points and continues to use the motor.

I’d be more than happy to be corrected on this. What have others experienced?

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Shamus

[Shamus]

Thanks Olcah,, I have resolved to do just what you recommend. Had a great chat with outboardnut today and am working up my courage to take off the powerhead and crack the block. All new to me.

[olcah]

You will be fine. It occurred to me that if you want to change the leg length you may need to change out the shift shaft. The only way to change it is from top of the leg with the powerhead removed. So if you have the part you should change it when you have the powerhead off. Just FYI the photo (of a 1956 Johnson RD18) shows the top of the shift shaft and attachment to the cross shaft from the shift handle. Photo also shows the end connection of the water tube where if connects to the engine block. I don’t know what is involved if you need to change the tube for a longer one as I have never messed with that.

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Shamus

[billy-j]

If I were you I would get a original paper evinrude parts catalog for a electric start of your model year. I like the original paper catalog as you can easily go back and forth to see how all engine components go together. Sounds like your engine is modified to be electric start. There is more involved in correctly making a motor electric start. The mercury safety switch is specific to the model year engine in big twins you can look up the correct # number and get one from a dealer in vintage OMC parts ( there are several hear you can deal with I deal with Dan Gano in spirit lake Iowa ). Also the carburetors are different Manual and electric start. Electric start carb has bottom that has place where choke solenoid mounts with loop bracket. you can use a 1957 solenoid which is 12 volts. Or the original 6 volt if you use 6 volt battery. Also carb linkage is different on electric start and manual start carb. and check your flywheel # number it’s on flywheel I know the number is different from 1955 to 1956 but they look identical . You need to know if your components are correct or if you have some that are incorrect. A parts catalog will help you figure it out. A lot of engines converted just had a starter and bracket put on and the owner would manually choke it and just hit a solenoid to activate starter and they were happy with that. Now you know.Regards Bill,

[Shamus]

Bill, that’s exactly what I have, I think. Just a 25018 modified with an electric starter. No choke solenoid, no mercury safety switch, standard carb. I”ve got an original parts catelog for the motor, but it was not listed as electric, so like you said some owner apparently modified it. The boat itself has an old Dunphy installed solenoid and start button but its pretty corroded and i don’t think it was ever really set up for electric start, just some optional wiring. But I wasn’t around when the boat was built, and only one when the motor was built, so I’m behind the eight ball (again)! Thanks for your insight.

[Shamus]

Olcah, thanks for the photo. I pulled off the extended water tube today – It had n extension which required that heating it up with a heat gun and then twisting it off. It had a type of joint with a lip which was apparently filled with some type of tar-like cement, but thankfully not solder. (Its just some 1/2″ or so copper plumbing pipe, so not a big deal if it had to be replaced). I’ll post some photos of it. As for the shifter, It did not have an extended shift rod,, but instead an extended shift rod connector, which I have never seen in any of the parts catalogs I have. I’ll have to get a standard size shift connector. Thanks for your insight!
Regards,
John

[olcah]

Shamus,
The lower end of the water tube is supposed to be cut off at an angle and it fits into the rubber bushing in the water pump housing. The tube is cut of at that angle for a purpose (venting the housing, sealing the shaft – I forget ) but anyway it does matter for proper pump operating and I just wanted to give a heads up in case the tube was moved. See Antique Outboarder July 2018 article “OMC Water Pumps”.

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Shamus

[billy-j]

Well what are you going to do ( electric start ) ? My thoughts. If your boat is small and you plan to tiller steer you are right there to choke manually just put a solenoid by the transom and a start button and I would wire in the mercury switch so you don’t get hurt with a wide open start. Or if you use controls and steering wheel I would get the missing components to fully make it electric start. Other wise you will be unhappy.

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Shamus

[Shamus]

Billy, I am going to try to get the proper equipment for electric start from the steering wheel, and will scratch around for the parts. My boat’s steering wheel is in the rear section anyway, so I can compromise on the choke for now. I’ve got plenty of time to decide – I live in Northern Minnesota, it was -16 degrees this morning, and my shop is poorly heated! Thanks for the advice, Its greatly appreciated!

[billy-j]

That’s a great looking wood boat . Looks good on trailer too. Good Luck. Bill,

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Shamus

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