1979 Evinrude 25 hp o/b

U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
1st off thanks for your help last time all, Have some oil questions, What exactly am I looking for in a lower unit oil when I drain it, what are the specs' and is any brand better than the rest what oil weight am i looking for? and the same question for the fuel mixture I believe I'm suppose to mix 50:1 , but I've heard other thoughts on the subject like 100:1 if I use amsoil. any 2 cycle marine oil work?
Prop questions what would work best for my 14 ft alum boat that I will mostly be using on the Snake River here In Idaho( Once I get a prop guard built for it) looks like a have a 9 in, 3 blade but havent measured yet since I just bought the boat and havent had time to play with it, I would just like to buy a backup one for emergencies and is there anything tricky about changing out props? Is it best to store the o/b up right in the winter, I will be storing it in my basement so not worried about cold weather.
 
bktheking

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1979 Evinrude 25 hp o/b

1- metal filing or water. Metal means something's going on inside, gears might be shot, who knows, check first. Water means either the lower unit seals are leaking or the plug gaskets are bad. As far as type I just go into my omc dealer and they gave me omc synthetic lower unit oil.

Run 50:1, 100:1 has been frowned upon since omc switched back to 50:1. Any marine 2 cycle oil will work, search the forums, people seem to have their preferences, some oils smoke less/cost more.

Props, i'm not expert on them, someone else will chime in.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

thanks, I bought amsoil for both, when I drained the lower unit, had water in it & it looked like it needed changed badly, noticed when I removed drain and vent screw that there wern't any o-rings, gasket and thought there should be? I also took my prop off, removed the pin and slid off prop checked out the spindles and all looked good all 13 were there, found a stamp that says 9.2x12 and wanted to know if that is my prop stamp, because I need to order another one but when I put the info in the system I cant find anything that matches that number the old one has 3 blades. thought the 1st number was for # of blades 2nd the diameter and 3rd is the pitch. Anyway If anyone can direct me to the prop that will work best for me I would be thankfull. what is the difference between commerial or non when I type in my motor info when I'm at the prop order page?
 
W

Whoopbass

Senior Chief Petty Officer
Joined
Jun 29, 2006
Messages
653
Re: 1979 Evinrude 25 hp o/b

Yes you need the nylon washers for the lower unit fill screws. You will need to get them at a boat dealer or possibly here on iboats.

That # is the diameter and pitch of your prop (9 1/4 X 12). Try and find a 12 pitch prop since your most likely not carrying heavy loads.
It looks like iboats doesn't have any 12 pitch props in stock (might give them a call and see whats up).

Commercial motors is just a no frills motor that I think OMC discounted for business use. Your lower unit is a non thru hub exhaust and OMC ended that style in the early 80's and went with thru hub exhaust from 84' on or around there but commercial outboards had the non thru hub exhaust lower unit at least until 89'. As long as your outboard is white (johnson) or blue (evinrude) it isn't a commercial motor since they are painted grey.

I ran a 1980 25hp Johnson in rivers for years. I busted up a lot of props. The good thing about aluminum props is they will usually break before they tear up your gears. I ran some pretty beat up props and never done any damage to the lower unit except possibly ruining the shaft seal. I ran it for years with milky lower unit oil but I did change it out every few trips.

I bought a Mack's river runner for my motor but never installed it. It looked like I had to drill right through the case where the oil sits and I wasn't liking that idea. If you buy one of them you better call them and get the scoop before ordering.

I always ran the cheapest tcw-3 oil I could fine (usually wal mart oil) (same for lower unit oil) and when I sold the motor the compression had an even 120psi on both cylinders and the lower unit gears looked like new.
Store the motor in your basement (so nobody steals it) and lay it on its back facing up.
If your motor is like mine then its bullet proof.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

thanks for the info, I plan on sitting on it for the rest of the year and just tinkering with odds and ends getting it ready for next year. I have ordered the manual for it but until it comes your ideas are great so I can start tinkering, any idea on what spark plug for that o/b? Instead of the river runner I'm going to get a circle prop guard for it they just look like they would protect the prop better. cant believe what it costs for a piece of steel pipe. lol
 
14ftgrumman

14ftgrumman

Chief Petty Officer
Joined
Jul 19, 2008
Messages
416
Re: 1979 Evinrude 25 hp o/b

I run Amsoil 100:1 mix in my 20 and 25 (both 1972's). went so far as to call Amsoil to make sure that I wouldn't burn up motor. That was 4 years ago. Not a problem with either of them. I use synthetic gear oil in both lu's. Just personal preference.
 
bktheking

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1979 Evinrude 25 hp o/b

This is from another site talking about mix and oils..

I have posted here many times about some two stroke oil testing our company did for Mercury Marine.

Bottom line,

32 to 1 provides all the protection possible in nearly every situation. Except very highly loaded engines such as 48HP 125cc Kart engines.

16 to 1 will result in more HP as will 8 to 1 if you can get it to run cleanly.

50 to 1 provides enough protection for many non racing applications but does result in very slightly higher wear rates of certain components in some high performance engines. This includes reed valves and crank bearings.

100 to 1 results in much higher wear rates regardless of type of oil used. It will also result in outright engine failure in many highly loaded racing applications. Kart engines and 500cc GP bikes are good examples of unsuitable applications.

My suggestion,

Use a quality TCW-III oil at 50 to 1.


I could undertand using 100:1 if you are strickly trolling with the motor, my 9.9 will be used for that. If I run into an emergency and need the kicker to get home I will swap lines and run the motor at 50:1.

If you are going to be running your motor wide open, play it safe and use 50:1with normal oil, you could run 80:1 with the amsoil, heard too many stories about motors burning up using 100:1.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

At the risk of being a retard I ask this question. How in the heck does this top cover come off to look at the motor? It is only a pull start and it looks like you can push in around the handle and that would be the only obstruction in the way from pulling it off, is there a locking device somewhere else, and does the rubber seal around the base come off with the top cover also? maybe I'm just not giving it enough levage because its new to me and didnt want to break anything.
 
bktheking

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1979 Evinrude 25 hp o/b

Look under the back of the motor under, there is a latch. And not a retard, don't insult yourself.
 
jasper60103

jasper60103

Commander
Joined
Sep 18, 2008
Messages
2,055
Re: 1979 Evinrude 25 hp o/b

yep, unlatch from the rear and lift the cover forward. I have an '81 Johnson 25hp. Lets see some pics of your rig.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

hey all. Like a dummy I couldn't wait for to buy a prop guard because the fishing is hot here in Idaho on the Snake River so I took the boat out for maiden voyage and 1 minute later hit a rock and snap broke off 3 blades like that. so it looks like I need to order 2 props, the nylon washers for the screws on the lower unit and 2 spark plugs and if iboats sells prop guards one of those too. can any senior member tell me part numbers for all this for my set up. I'll try to get some pics on here too. A good point was the engine starts right and runs good.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

I think this is going to be an expensive adventure? any ideas on the post above this one!!!!!!!!!!!

Does everyone agree that a 9 in prop is the right size, the one I broke measured 7 but I guess it could have been worn down over the years???? I cant find where it will let me order anything under a 9 in thats all that comes up after I type in the info
 
jasper60103

jasper60103

Commander
Joined
Sep 18, 2008
Messages
2,055
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

Here is where I'm at now, I bought a 12 1/2 in piece of stainless steel pipe that I'm going to have welded to a plate and bolted on to the lower unit and use as a prop guard, the local dealer has a 10 in or 12 in prop for 90.00 and I'm leaning towards the 10 inch but dont know if that will throw off the RPMs' too much? Any thoughts, the old one that busted measured out 7 1/2 in from tip of blade to blade, but it was the original probably and very worn.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

Looks like there is still no 12' pitch here on iboats, would it be o.k. to change the pitch to 11. I had the prop guard built and put on at the weld shop today, made a mistake and thought the I needed a bigger diameter prop and had them build a 12 inch stainless steel ring when the diameter of the prop is only 9.2 or 9 1/4 in. Do you folks think I should change the diameter of the prop guard to like 11 in or just try it? Looks like the guards sold on the net are 2 inchs bigger than the prop.
 
U

utilities

Cadet
Joined
Oct 8, 2009
Messages
12
Re: 1979 Evinrude 25 hp o/b

new prop doesnt look so new, the guard saved it but still has a few good nicks in it, guess this set up just aint going to work on the river.
 
E

Elbo

Petty Officer 2nd Class
Joined
Sep 12, 2009
Messages
136
Re: 1979 Evinrude 25 hp o/b

Ive heard many people talk about storing their motors upright.The fact is in a 2cycle engine there is no oil in a crank case.The only lube you have for the engine is what you put in the gas. have always used 3oz. per gal. as a rule.No matter unless the engine spec. calls for more.That engine is designed to run at all angles except inverted.It will do that if you use a slide type carb.What im saying is this engine has to run in white cap situations,high waves ,jet skiers like to go abit neg.when they can by jumping the tallest wave they can and these engines still have to perform correctly.You can stand these motors on their heads and it should not matter.When I store mine ,the last run I know Ill make this year,I pull the tank hose off and let it run till it dies.That way there is no old gas to varnish or jell.My 2 cents worth
 
bktheking

bktheking

Vice Admiral
Joined
Jul 29, 2008
Messages
5,057
Re: 1979 Evinrude 25 hp o/b

I use fogging oil at the end of the season, leaves the internals nicely coated to prevent rust and helps with dry starts after extended storage.
 
You must log in or register to reply here.
Top