1976 Evinrude Carb question

Hey guys.

I've got a 1976 Evinrude 15HP. The motor starts great, idles great and runs...kinda great. I've got a 15' tin and it only pushes it about 8 MPH. I'm not expecting 20+ but I think it should be getting above 10! Maybe a solid 15 MPH? I wasn't loaded down..it was just me.

So I'm thinking maybe the carb is stopped up somewhere. Does this sound like the case...or possibly a good start?

Some guidance would be greatly appreciated.

I was looking at carb kits and knowing my problem, I pose this question:

Do I need a carb kit with or without a float kit?

Check out this link.

https://www.sschapterpsa.com/ramblings/Johnson_9.9_carb-fuel_pump.htm

Give a few more details if you could. Does the motor sound like it is revving up as it should or is it lugging down? The transom and motor length match? If you do end up needing a carb kit, I would change the float also.

Ya it should push you better than that. I had a '76 9.9 w/ 15hp carb and it would push my 14/48 with gear about 13-14mph but it would struggle to get on plane.

Umm..the motor sounds great. It's sluggish starting out...and then stays sluggish I guess. I've never had a motor like this before so I'm not exactly sure what it should do.

Transom and motor length...? I'm not sure I know what you mean.

Thanks for the link. I'm still reading on it.

Transom length, what I was referring to there was maybe a short shaft motor on a tall transom, but you said the motor stays sluggish so I don't think that would be the issue. First thing I would check is to make sure I am getting fire to both plugs, if you are down a cylinder that could do just what you are describing.

Humm...is there a good way to test for fire without holding the plug

You can buy cheap spark testers at most auto parts or small engine stores ($6-15). You should be able to jump at least 1/4 inch. You can also try running the engine, pulling one plug wire at a time to see if it makes a difference (I would pull the plug wire before I started the engine). Is this engine new to you? Have you checked the compression to make sure that is good? Have you pulled the flywheel to see how things look under there? Assuming the engine is a 76 model you might only need a new set of points or an adjustment to the current ones.

Yes this motor is new to me. I have no idea about points or any thing like that. I would be comfortable pulling the carb and rebuilding..but I'm not sure how I feel about working on the firing system.

What compression should I be getting? I am picking up a compression gauge at lunch to test it. I don't know if I wanna know or not though!

I don't know exactly what should be a good compression on that particular engine, I usually tinker with the older models 55-70's, but I would guess something around 90 or so with both being within 10% of each other, I'm sure one of the other guys with more experience on these engines will let you know. Let's first check the compression then check to see what you got for fire then go from there.

Got 118 on top, 105 on bottom

Those numbers would sound OK to me.

Me too...but what do I know!

Tried to buy a spark tester...no1 in my town has such a device. BOO! Checked AutoZone, Orilies, Napa...nada. Is there a good way to verify without one? I'm going to try starting it with one plug disconnected at a time. Should it start with either cylinder?

Yes (it should start), you might also check the plugs, you might find one that is clean, so to speak, and the other oil/gas fouled, if so I would try to figure out why that one is dirty (bad plug, wire, coil, points??).

Well,

I tried what you said and took one plug wire off and started the motor. then the other. it fired on both cylinders so im guessing i have adequate fire. no fooling on either plug..just changed them before i took the boat out the first time. ran it for probably 15 minutes. I took the carb off and inspected it. the float looked pretty old...but it is working. the needle under the float looked good. i blew all the openings with my compressor and ran a wire down the needle in the middle. The gasket under the bowl looked worn ..but all in one piece.

What do you think?

Took the boat out tonight after i "cleaned" the carb ( dunno if what i did was actually considered a cleaning )

Same speed. 8 mph. changed the tilt/trim. only lost speed. its like the boat won't come out of the hole. I did go sit on the bow and reached 11mph.

do you think I should rebuild the carb and distribute my weight differently? Are my speed expectations too high? My tin is a 1548 and pretty stripped.

Check your linkage and make sure your throttle is opening all the way. Would you happen to have a friend that has a similar size engine you could try on your boat to see how it runs?

I've got a buddy with the exact same size but its a 95 model. I don't know if he'd let me use it

Make sure the carb butterfly is opening to full throttle. I had the same thing on my 76 35hp someone in the past had adjusted the linkage so it only got about 20 percent throttle.

CanoeCraft said:

Make sure the carb butterfly is opening to full throttle. I had the same thing on my 76 35hp someone in the past had adjusted the linkage so it only got about 20 percent throttle.

Click to expand...

How do I do that?