1956 Evinrude 7.5 hp operation

[wbeaton]

I have what is probably a stupid question, but...

I recently bought a 12' tin boat that came with a 7.5 hp Evinrude Fastwin with no operators manual. I took the boat for a spin before I bought it. It started with no problem and ran great. After getting it home I noticed a "shift" position on the throttle arm. Am I supposed to set this to "shift" before I change gears?

 

[Laddies]

Re: 1956 Evinrude 7.5 hp operation

The shift position on the throttle arm on many of the engines don't line up to well just idle it dowm to a reasonable speed and shift it. Alway mis your fuel 24 to 1, plugs are gapped at .025 and points at .020 they are great old engines, keep your eye on the gear lube till you know the lower unit is not leaking, thats the death of most of the older engines

 

[wbeaton]

Re: 1956 Evinrude 7.5 hp operation

Thanks Laddies,

That is what I did (as always). Thanks for the numbers. I was just trying to find them.

 

[Texasmark]

Re: 1956 Evinrude 7.5 hp operation

The start position was just to insure that you had the throttle opened some as they didn't like to start at idle, being only 2 cylinders.....my grandpa had one of about that year.

Wasn't any biggie. If you were too slow it wouldn't start and too fast it would race like crazy when it lit off and you had to be fast on the throttle to cut her back.....then it would go pop pop pop pop as it was slowing down.

Mark

 

[Texasmark]

Re: 1956 Evinrude 7.5 hp operation

As I recall, later on they (or maybe it was my Merc) had a stop for starting (so that you didn't overrev) and as long as you were in N you could only advance the throttle to the stop for starting. Once in F gear (or R) it would rev all the way up.

Mark

 

[wbeaton]

Re: 1956 Evinrude 7.5 hp operation

Johnson/Evinrude have the feature you mention, Texasmark, but not this early. I think it came out a couple years later.

I've had this motor in the tank a couple times now and I have a pretty good understanding of it. Unfortunately, I have to rebuild the carb and fix the air line. It starts and runs great, but its a little rough at idle and the low idle was over tightened in what would seem to be the closed position, though it still runs. I couldn't turn the low idle knob at all, not even after backing out the packing nut. It took some heavy torque with a set of vise grips to unscrewed the needle valve and it still looks ok. It has slight shoulders from being overtightened, but its not bad. However, adjusting the valve does nothing. It won't idle below start and the handle does line up well with the markings. Slight air leak at the gas/air line connection, though it doesn't seem to affect the motors operation.

Lower unit was full of water when I checked it. I refilled it and it holds oil well and no water entered the lower unit when it was in the tank. This weekend will be the real test when I put it on the water.

 

[Texasmark]

Re: 1956 Evinrude 7.5 hp operation

Thanks on the start pos info.

Funny, I seem to recall problems with needle valves on those old OMC's when I was young. As I recall, you had to keep the nut tight to keep it from leaking but that made the shaft hard to turn and the spline in the knob would strip out so you couldn't turn the shaft.

My opinion on the damaged needle is that it's useless if it's deformed. BTDT many times.

You might decarb this engine and be pleasantly surprised at the results. Being that old it has to be carboned up.

Mark

 

[wbeaton]

Re: 1956 Evinrude 7.5 hp operation

I had it out on the water today and it idled nicely, though adjusting the low idle did very little. When idling I had to keep the throttle turned up to start any less and it stalls out. Maybe its in the linkage.

I agree about the needle valve, but it'll do until I rebuild the carb this winter. I think I can repair the needle. I'd bet what you remembered about the low idle adjustment is right on.

I've been thinking about decarbing. How do you suggest I do it? Can i use a product like Seafoam in this machine or should I just open the head and clean it by hand.

 

[Texasmark]

Re: 1956 Evinrude 7.5 hp operation

Grin on the stripped adjustment. Sorry , but true as you apparently know.

Go to search on this site, search the subject debarb, and they tell you.

Want more, ask,

Mark

 

[tmcalavy]

Re: 1956 Evinrude 7.5 hp operation

Might also want to dump a can in your fuel tank and run it out pretty soon. I've got a 58 Johnson 18 hp that runs a lot better after three gallons of seafoam-enriched go juice.

 

[Paul Moir]

Re: 1956 Evinrude 7.5 hp operation

The low speed control not seeming to do anything would suggest to me that the idle circuit in the carburetor is clogged.

You might be able to glean a little extra information from here:
Click here
It's for older 7.5s but some of it should be helpful.

 

[wbeaton]

Re: 1956 Evinrude 7.5 hp operation

Thanks everyone.

Thanks for the website Paul. Looks like the 1953 motor has the same powerhead and carb as mine.