Help w/ Outboard ID

So I just bought an outboard for my new Alumacraft 1232 flatbottom. The seller advertised it as a 1987 Evinrude 9.9. When I was looking at it, I was so busy checking compression and examining the cylinders, pistons, and spark plugs that I forgot to run the model number. Now that I've made it back home, the model number is marked E15RCDE, which codes for a 1986 Evinrude 15. However, the engine cover says 9.9 and my research shows it to be a 1987. The seller recently put a new carb, water pump, etc. in it. How do I determine which one I have? Since the two motors are so similar, would it be an issue if it is a 15 and the new parts he put on were for a 9.9? Obviously if the engine cover turns out to be the only '87 9.9 part on it I won't be concerned, but should I be if it turns out that other parts are mismatched?

Also, as an unrelated question, I read that there had been issues with the 100:1 mix used in some of these engines. I saw that OMC released a bulletin in the late 80s and that shops just swapped the 100:1 label with a 50:1 decal and told owners of the change. Should I keep putting 100:1 in it or should I switch to 50:1?

Thanks for your help

The only difference in the 2 motors i have found is the cylinder and carberateur, as the impeller is the same in my experience.
As I like to err on the side of caution, I have several outboards and I run them all at a 50:1 mix without issue other than a11958 18 hp Fastwin which runs on a 24:1mix.
Seems like 100:1 is to thin IMO and not worth risking damaging the power head over a few extra ounces of oil.

I picked up a 9.9 which has similar issues. Alot of parts are interchangeable ,but if the tag says its a 15 I'd be willing to bet its a 15 with a 9.9 hood. ALWAYS run oil mix at 50:1 This link will help you alot. Good Luck and enjoy
Oh and a 1232 with a 15 on it ...........man that rascal is gonna FLY :mrgreen:

https://www.leeroysramblings.com/

NEVER run that engine on 100:1. It will not leave enough of a film of lubrication on the cylinder walls or needle bearings during storage. Also it will leave you no protection during an overheat compared to 50:1 or slightly heavier mixture.
The cowling is not a good indicator of horsepower. Many folks changed that to comply with the 10hp max limits imposed on many lakes.
The model # indicates your engine is a 1986 15hp.
There are no physical differences in the cylinder & crankcase or rotating mass between the 9.9 and 15.
The differences are the carburetor, extra shim under the reed stops, and an exhaust tuner vs an exhaust pipe. This varies a little in later model engines.
If the PO changed out the carb he may have installed a 9.9 carb. Simplest way to find out at this point is to ask him!

I would agree with the good advice offered here, especially NEVER RUN 100:1

In addition, I would check the ID plug on the block itself. See if the engine is complete with matching ID numbers. The plug should match the ID tag on the mounting bracket. At least you'll know what you're starting out with.

If its a real 15hp, you will have the correct 15hp parts. These include the carb(maybe), the exhaust tuner, exhaust housing, and reeds.

The exhaust housing itself is different too as it forms the other half of the "expansion chamber". The 2 exhaust outlet holes in the bottom of the aluminum casting are actually smaller than the three holes that mate up with the 9.9s square tube. This is also why there are two different water pump grommets in the repair kits.

These engines should be propped to run about 1000 rpm higher than a 9.9. Ie 6500-7000rpm max, or whatever is spec'ed for your year.

100:1 No! Run it at 50:1 and if it smokes a lot, starts fouling plugs and dies at idle than back off the oil a little bit.

Wow thanks for all the replies. I knew I wouldn't be able to contact the seller last night and began to worry he might start ignoring my messages if I brought that up. However, I contacted him this morning and he said that the engine cover was on it when he got it. I examined several other parts that I saw on the ramblings webpage that should differ between a 9.9 and 15 and all I found showed to match the 15. I asked about the parts he installed and he said that he had ordered them from the model number rather than just asking the guy behind the counter for parts to an "87 9.9." So everything but the cover looks like a 15 horse, and boy does it ever fly. Tested it today on my 100x40 yd pond and had water coming over the gunwale at the first turn. I think lubing the throttle to make it more sensitive may help so that I won't have as bad of an all or nothing feel to it. It's also awkward to steer being left handed, but I guess I'll get used to it.

As for the oil, I saw the problems where there were head issues with heavy use/high rpm and the issues with rusting in storage. I'm not going to run 100:1 in it, so don't worry. Between hunting season and fishing, it won't see much storage, and on a 12' I can't begin to test it's limits. When I asked the previous seller his thoughts, he said he'd do 80:1. I had thought about just 75:1, so that might be where I start and adjust from there.

Thanks again

Once again......run 50:1. Your Johnson/Evinrude engine was manufactured by OMC.
OMC tried 100:1 on the production engines around your vintage and backed off when they saw engines exhibiting accelerated wear characteristics after prolonged storage.
OMC then sent out a bulletin to all dealers to remove the 100:1 stickers on the engines and inform all customers to go back to a 50:1 mixture.
DO NOT go by what the previous owner said. At best he was ill-informed and definitely not in the know.
This engine will run all day and run well on as much as 24:1 if you so desire with very little smoke and no fouled plugs. Run at least a 50:1 mixture and your engine will last a lot longer.

50:1 ratio will be best

Ok I'll do 50:1 then.
I found the original bulletin online and asked the PO about it. He just works on a lot of motors so I assumed he'd know more about it, but apparently he just runs off of the model numbers to get parts and installs/works on them that way. I just didn't know if I should go somewhere between 50:1 and 100:1 as I thought they would have been designed to run on a leaner mix. But I'll try the 50:1 or just slightly higher as I tend to be a bit heavy when pouring oil, which seemed to be a little hard on the last outboard I was using.

It is best to be a little heavy on the oil than a little light.

I have that same motor and the only way to run 100:1 is if you were going to use the Amsoil that is designed to be used at that mix ratio. Which is what I now use.

May do you well to read the profiles of those who are trying to help you.
May answer the question as to whether or not OMC designed the engines differently to run on 100:1...........hint, they did not!
That whole fiasco was due to marketing dept. trying to increase market share more that it already was back then. Engineering had nothing to do with that decision and was against it the whole way. Engines were never designed differently for it.

That's what I didn't know. With it being labeled 100:1 I think I was justified in assuming that it was designed to run on a lesser oil mix. Most companies would only label something like that when the product is designed to that specification. (i.e. Some vehicles are labeled on the gas cap to use a minimum octane fuel.) I didn't intend to seem like I was questioning any advice, either. That's why I would ask a question anyway.
In any case, the fuel given to me by the PO looked and smelled like it might not have been 100:1 like he said, so rather than risk it and add oil to make it 50:1 I trashed it and refilled the tank and a couple cans with my own 50:1 mix. I also made a nice laminated chart with the oil I should add for a 50:1 mix for all of my gas cans and tanks of varying capacity.
Thanks guys

Well I'm glad you heeded sound advise thats been given kstrayhorn. To reiterate what pappy was saying I pulled apart a 1991 25hp Evinrude. I have known the owner for more that 20 years and I remember when he brought this motor new in the box. The crank shaft, pistons and all internal parts have a good coating of oil on them. Now this engine was used for many years on a hand built 20 ft wooden skiff. It was a work boat, used for hauling nets,crabbing , digging for oysters when in season. The owner always ran at least 50:1 mix or better. It has sat unused for quite a few years and like I stated , all the internals had a very good coating of oil. Crank shaft,main bearings and piston bearings shows VERY little wear. I dare say that is engine has 2000 hrs on it. :shock: It was run 5 to 6 days a week for years,rode hard and put up wet :LOL2: I have some pics I'll post up later if any wish to see.