Classic '71 40HP Evinrude Troubleshooting Question
 

Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

I've changed the plugs and poured some seafoam into the tank and ran
hard on the lake for a good afternoon, but neither seemed to help the issue.

Any suggestions on what to do next?

Thanks,

Ryan

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I have
the cover off the motor, I can actually feel air blowing back out of the
carb

Thanks

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/15 3:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

I've changed the plugs and poured some seafoam into the tank and ran
hard on the lake for a good afternoon, but neither seemed to help the
issue.

Any suggestions on what to do next?

Thanks,

Ryan


Dirty carbs, low speed carb needle adjustment?

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I have
the cover off the motor, I can actually feel air blowing back out of the
carb

Thanks


Bad reed valves.

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 3:38 PM, Mr. Luddite wrote:
On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I have
the cover off the motor, I can actually feel air blowing back out of the
carb

Thanks





Bad reed valves.

Forgot to mention why I mentioned the reed valves. I had a 70hp, 2
stroke Evinrude of about the same vintage. Exhibited exactly the same
symptoms ... ran fine at higher RPM but at idle it would "sneeze", miss
and stall. The problem was the reed valves that are the 2 stroke
versions of a 4 stroke's input and exhaust valves.

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 2:27 PM, Keyser Söze wrote:
On 8/24/15 3:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

I've changed the plugs and poured some seafoam into the tank and ran
hard on the lake for a good afternoon, but neither seemed to help the
issue.

Any suggestions on what to do next?

Thanks,

Ryan


Dirty carbs, low speed carb needle adjustment?

The carb IS due to be cleaned, for sure. That's a project for when I
have time to learn on the fly. I was hoping that if it was carb problem
(that just developed) the SeaFoam would clear it up.

As for the needle, adjusting the needle doesn't effect the problem,
except as it relates to increasing the idle speed.

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 2:47 PM, Mr. Luddite wrote:
On 8/24/2015 3:38 PM, Mr. Luddite wrote:
On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I
admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I have
the cover off the motor, I can actually feel air blowing back out of the
carb

Thanks





Bad reed valves.

Forgot to mention why I mentioned the reed valves. I had a 70hp, 2
stroke Evinrude of about the same vintage. Exhibited exactly the same
symptoms ... ran fine at higher RPM but at idle it would "sneeze", miss
and stall. The problem was the reed valves that are the 2 stroke
versions of a 4 stroke's input and exhaust valves.

That doesn't sound like fun... It looks like I would have to pull the
carb to MAYBE see them, and probably the reed block. Did you replace
them yourself, or find somebody to do it?

Maybe I should consider selling her to somebody else as a parts motor. :)

Classic '71 40HP Evinrude Troubleshooting Question
 

On 8/24/2015 4:36 PM, Ryan P. wrote:
On 8/24/2015 2:47 PM, Mr. Luddite wrote:
On 8/24/2015 3:38 PM, Mr. Luddite wrote:
On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I
admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I
have
the cover off the motor, I can actually feel air blowing back out of
the
carb

Thanks





Bad reed valves.

Forgot to mention why I mentioned the reed valves. I had a 70hp, 2
stroke Evinrude of about the same vintage. Exhibited exactly the same
symptoms ... ran fine at higher RPM but at idle it would "sneeze", miss
and stall. The problem was the reed valves that are the 2 stroke
versions of a 4 stroke's input and exhaust valves.

That doesn't sound like fun... It looks like I would have to pull the
carb to MAYBE see them, and probably the reed block. Did you replace
them yourself, or find somebody to do it?

Maybe I should consider selling her to somebody else as a parts
motor. :)


I had a pro fix it. I am not a mechanic by any means.
The "sneeze" is really backfiring through the carb because the reed
valves are worn and don't seal at low rpm.

Your problem could be something else obviously but worn reed valves will
cause exactly the symptoms you have.

The one I had ran great after they were replaced. A lot cheaper than a
new motor.

Classic '71 40HP Evinrude Troubleshooting Question
 

On Mon, 24 Aug 2015 16:44:58 -0400, "Mr. Luddite"
wrote:

On 8/24/2015 4:36 PM, Ryan P. wrote:
On 8/24/2015 2:47 PM, Mr. Luddite wrote:
On 8/24/2015 3:38 PM, Mr. Luddite wrote:
On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I
admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I
have
the cover off the motor, I can actually feel air blowing back out of
the
carb

Thanks





Bad reed valves.

Forgot to mention why I mentioned the reed valves. I had a 70hp, 2
stroke Evinrude of about the same vintage. Exhibited exactly the same
symptoms ... ran fine at higher RPM but at idle it would "sneeze", miss
and stall. The problem was the reed valves that are the 2 stroke
versions of a 4 stroke's input and exhaust valves.

That doesn't sound like fun... It looks like I would have to pull the
carb to MAYBE see them, and probably the reed block. Did you replace
them yourself, or find somebody to do it?

Maybe I should consider selling her to somebody else as a parts
motor. :)


I had a pro fix it. I am not a mechanic by any means.
The "sneeze" is really backfiring through the carb because the reed
valves are worn and don't seal at low rpm.

Your problem could be something else obviously but worn reed valves will
cause exactly the symptoms you have.

The one I had ran great after they were replaced. A lot cheaper than a
new motor.


I would try the carbs, it can't hurt but I think Richard is right.
Lots of cranky 2 stroke problems get back to the reed valves.
I did therm on my 75 Merc. After you get all of the carb linkage
loose, it is not that many bolts to get the manifold off and get to
the reed block. I usually get a few plastic bowls and keep the parts
from each stage of disassembly in another bucket. That helps when you
are putting stuff back together. Taking pictures is good too..

Classic '71 40HP Evinrude Troubleshooting Question
 

On Mon, 24 Aug 2015 15:36:12 -0500, "Ryan P." wrote:

On 8/24/2015 2:47 PM, Mr. Luddite wrote:
On 8/24/2015 3:38 PM, Mr. Luddite wrote:
On 8/24/2015 3:25 PM, Ryan P. wrote:
On 8/24/2015 2:18 PM, Ryan P. wrote:
Hi All,

I have a 1971 40 HP Evinrude (model #40152B). I bought it used a few
years ago, and its actually been a great runner even though I
admittedly
abuse it maintenance-wise. Damn thing starts up quicker and more
reliably than my '85 Merc...

Anyway, this year, its started "spitting" and "coughing" at low RPM's.
When throttled maybe 15% past idle, it sounds great. If the gas were
bad or the oil mixture not right, the RPM's would not matter, correct?

For the record, the sound is similar to a sneeze, actually. If I have
the cover off the motor, I can actually feel air blowing back out of the
carb

Thanks





Bad reed valves.

Forgot to mention why I mentioned the reed valves. I had a 70hp, 2
stroke Evinrude of about the same vintage. Exhibited exactly the same
symptoms ... ran fine at higher RPM but at idle it would "sneeze", miss
and stall. The problem was the reed valves that are the 2 stroke
versions of a 4 stroke's input and exhaust valves.

That doesn't sound like fun... It looks like I would have to pull the
carb to MAYBE see them, and probably the reed block. Did you replace
them yourself, or find somebody to do it?

Maybe I should consider selling her to somebody else as a parts motor. :)

Internet is your friend.

https://www.youtube.com/watch?v=CdMepf8PwfY
--

Ban idiots, not guns!