evinrude big twin 25

[cjkbigtwin25]

Hi i just bought a evinrude big twin aquasonic at an estate sale for 25 $.
The guy said it was siezed but i got it home and put wd4o in the cylinders and it loosened it right up. I tried to start it and i primed the cylinders by dumping gas into them. All i got was a couple of backfires and nothing else i repeated this 3 or 4 times and still the same. It has great spark but it just doesnt want to run any help would be appreciated
thanks, colin

 

[fireman57]

Re: evinrude big twin 25

If you will post the model number of the engine that would help. If it is an electric start I would check the compression on the cylinders and post them. If it is electric start then you can also check for spark. No yellow or orange it must be blue. The guy could be right and it could be siezed. WD40 is not a lubricant. Use premix in a squirt bottle and shoot it into the carbs. Don't use straight gas as you are doing more harm.

 

[cjkbigtwin25]

Re: evinrude big twin 25

i know about using the 50:1 fuel ratio i didnt try starting it with wd 40 i had the plugs out and was turning it over by hand. it has blue spark. the model# is 25018-07228 thanks

 

[fireman57]

Re: evinrude big twin 25

Sounds like all you need to do is take the carb off, soak it, blow all the passages out with compressed air. If it has set for a while you probably have "varnish" in the carbs. I think the rebuild kit is only around 20-30 bucks. You also want to make sure that your float is level to the carb when it is turned upside down.
I think that the reason that you get a backfire instead of running is that either you are getting too much or too little when you try to dump fuel in the cylinders. have you had the carb off yet?

 

[cjkbigtwin25]

Re: evinrude big twin 25

no not yet i will probably get around to it tomorrow how much do these engines usually sell for this ones in pretty good condition thanks

 

[fireman57]

Re: evinrude big twin 25

It depends on the area and who needs one now. they sell for a lot more running than not. You only have 25.00 in it. I you can get it running for another 20 or so it triple the price rather than selling it for parts. If nothing else, selling it for parts still nets you a decent profit.

 

[cjkbigtwin25]

Re: evinrude big twin 25

thanks that helps alot i want to find an old rowboat and make a little river runner to fish and explore

 

[samo_ott]

Re: evinrude big twin 25

Better be a big rowboat to put a 25hp on it! A 25018 is a '55 model. The last year of the 25hp and the quietest version. Have you checked the spark with a spark tester? Ensure you have good strong blue spark that will jump 1/4". Don't test it by holding it against the block. Cleaning the carb is always a good idea also.

 

[1946Zephyr]

Re: evinrude big twin 25

24:1 is the correct mixture for that motor. I think the best thing to do, is check over the ignition system and make sure everything is good. The coils should be new and no cracking, or they will need replacing. The points should be polished and set at .020 Run J6C spark plugs.

It's amazing that you got the pistons freed up that quick and easy. It must not have been stuck very long.

 

[tmcalavy]

Re: evinrude big twin 25

Pull the flywheel and check points/coils/condensors and flywheel key...key could be sheared if it was backfiring. Should always check these things, plus compression and impeller on the older motors.

 

[jimmacl]

Re: evinrude big twin 25

Could your top and bottom plug wires be reversed? Should run when squirting fuel in the carbs. Sounds like timing check the point gap.

 

[cjkbigtwin25]

Re: evinrude big twin 25

ok will do thanks

 

[cjkbigtwin25]

Re: evinrude big twin 25

Well today i took the flywheel off the bigtwin and wasnt surprised at what i saw the coils were all cracked and rusty the points didnt look bad where can i find the coils for a reasonable price should i also get points? Thanks again colin

 

[tx1961whaler]

Re: evinrude big twin 25

Coils and points are available here at iboats:
http://www.iboats.com/mall/partfind...gd_poid=109172&gd_row=82&**********=129258177
http://www.iboats.com/mall/partfind...gd_poid=111576&gd_row=19&**********=129258177
Impeller:
http://www.iboats.com/mall/partfind...gd_poid=109115&gd_row=29&**********=129258177
Carb Kit:
http://www.iboats.com/mall/partfind...gd_poid=109330&gd_row=33&**********=129258177

 

[1946Zephyr]

Re: evinrude big twin 25

Coils are available just about everywhere OMC parts are sold. Auquasonic 25hp Evinrudes are 1955 models. 1954 and earlier are not Auquasonic motors and 1956 was a 30hp so that narrows it down.

You clean that mag plate entirely and replace the coils and wires, that thing will run out from under you. LOL

 

[DJ]

Re: evinrude big twin 25

that thing will run out from under you. LOL

They were VERY strong for a 25.

 

[1946Zephyr]

Re: evinrude big twin 25

Yep, good sturdy motors with a 35.7 cube displacement. I had a couple in the past and I liked them.

 

[Chinewalker]

Re: evinrude big twin 25

Also, being that it came from an auction with uncertain past service history, do the waterpump while you're at it... CHEAP INSURANCE!

 

[1946Zephyr]

Re: evinrude big twin 25

Yes, I second that motion. Impellers degrade pretty quickly from sitting and who knows how long yours has been sitting. If it was slightly stuck when you got it, then it's a pretty safe bet, at least 10 or 15 years.

Also, check the oil in the lower unit and make sure there is no water intrusion. It will have a milky white appearance.

 

[loosecounty]

Re: evinrude big twin 25

You are going to need a pump impeller so pull the lower unit. While you are at it open up the lower unit and clean/ inspect all the gears and bearings. I have this very lower unit on my bench right NOW. Almost all these old OMC lower units leak so "breaking the seal " means nothing to me. You dont want to fire up an engine with a lower unit full of rust and funk, it will just help to ruin it. Remember , even when the shifter is in nuetral ALL three gears are turning at the rate of the engine, so a rusty mess is bad jew jew. Dont worry , it will only take a half hour of going over the gears to make you think "is this all there is to these things"? I always crack into lower units in these old OMC's and they are stupid simple, ...in an awesome way. Great engines! I have had good luck resealing these things with a super thin layer of RVT silicolne on all the mating surfaces. Like MAX says , " exspect these lower units to leak a little and just change the lower unit lube often" ......and especialy before freezing weather........TRUST me on this one. These are very robust lower units and chances are , even if yours isn't in great shape,(whith a little tlc and cleaning) it will still work for as long as you are interested in running it. As far as the rest of the engine ...if its an old omc and it has compression ....you can make it run! good luck!