Fuel oil mix for an old firestone 7 1/2 horse

[gearbomb]

I just enherited an old Firestone outboard 7 1/2 HP motor from my lol great grand pa. Its in great condition amost looks like it was never used well the paint isnt the best. I looked on the motor it said to use 1/2 pint to one gallon 30 weight oil. I did what it said and ran the engine for 5 or so minutes and created a nice smoke screen for my neighboor hood to enjoy. I think that modern oils must preform better then the older stuff. I dont want to ruin the motor so what mixture and of what should i run in it and what fuel should i use? I live in minnesota and here we have manditory 20% ethonal achohal in our gas. Thank you very much for your time in answer in this post.

[ranger69dv]

The old trusted 50:1 is always a good way to go. Thats 3 oz 2 stroke oil to 1 gal of gas.

[maverick1]

Just so you know there is some gas stations here in Minnesota that has non-ethanol gas. Minnesota states that if it is for small engines, off-road vehicles, etc it does not have to contain ethanol.50:1 might be too diluted. I have a 56 Johnson 7.5 and that recommends something like 24:1. Use TCW3 2 cycle oil (basically most 2 cycle oils out there).

[JB]

Do NOT use 50:1 in that engine unless you are trying to blow it up.The instructions are for 16:1, so I would not, in any case use a leaner mix than 24:1. In 1964 OMC announced that its 16:1 engines could be run on 24:1.Not sure what manufacturers actually made Firestone engines, so we need more information on your engine to make responsible suggestions.Is it 1 or 2 cylinders?Is it air or water cooled?Is there any manufacturer info on the engine? Model #, etc.?Let us know and we can give you good advice.

[tmcalavy]

JB hit the nail on the head. Your Firestone is probably a Scott-Atwater outboard, rebadged for Firestone. Use 16 or 24:1, using a good brand of TCW-3 outboard oil. The smoke screen was from using the 30W auto oil. Your motor requires richer mix than 50:1 cause it probably has bushings instead of bearings (ball or needle bearings). That was the technology of the day. Bushings only work if there is enough oil to keep the moving parts separated by a thin film of lubricant. You'll burn it up quick at 50:1. Check out www.scottatwater.com and see if your motor looks like any of those on that site. Post a model # and we can tell you the year...look on the transom bracket.

[gearbomb]

Ok first thanks for all the replys. This resource is one of the best. The motor has is a 2 cylinder. From what I can tell it is either a 45 or a 54. I am leaning more to the 54 because it has a small metal plate stamed on to it for registration in 54 from ohio. As to weather or not it is watercooled that is something I am unable to determin. It has some holes in the back of the the shaft bout I only saw smoke coming out of them. I didnt notice a jet of water spraying out of the back like most modern motors.[edit] It dosent look like the pictures from the 1949 models that was on that scott water web site which makes me almost sure its a 1954.

[gearbomb]

yep its a 1954 i figured out how to match the model number up corectly which is 10-A-103, 7.5 Hp. I hope that helps and thanks again for any help given.

[gearbomb]

I played with the motor today and I can say that it is a water cooled motor.

[Fouled Plug]

Next step, replace impeller.

[gearbomb]

lol i hate to ask anouther question but whats impeller? I was planing on replacing the fuel lines and opening up the gearbox but if you have some good advice I will be sure to follow it.

[tmcalavy]

The impeller is what makes water cooling possible. It is a rubber piece that forces water into the system for cooling. I'll look in my S-Atwater manual tonight and see where your water pump/impeller is and post back. They're generally pretty easy to replace on most outboards, and generally cost less than $25. Don't run it until you get the impeller changed, and never run it out of water...doing so will burn up the rubber impeller. You can run it at home by putting in a barrel or trash can full of water...the water should come up to the water intake/inlet on the lower unit.

[steelespike]

10 A 103 indicates 53-55. 1/2 pt to a gallon mix. .020 Point gap. Check with the scott guy at:web.a-znet.com/~scottguy/ or Laings at:www.laingsoutboards.com

[tmcalavy]

The water pump/impeller is on the drive shaft just above/below the cavitation plate...that horizontal plate that is part of the lower unit. You can probably find an impeller link at the scott atwater website. Never done one of these, so I can't tell you how to pull the lower unit...maybe the scott guy can. Let me know if your interested in a manual...I know a source.tmcalavy@llano.net