edd_barker
Cadet
- Joined
- Sep 8, 2009
- Messages
- 22
Hi all,
I have recently restored to life my friend's 1979/80 Evinrude 4HP, which he inherited from his Grandfather. It is a European model no: 49B36D, which Dan Gano (who supplied the parts) identified as a 1979 motor (4904/4932/4933) but with the points ignition from 1980/81, the E-4 models. The motor had not run for many years, the following was inspected and serviced before attempting to fire her up:
Flywheel pulled, ignition parts inspected. All looked brand new, even the coils. Points set to .020. HT leads, caps and spark plugs replaced. Spark tested and looked good.
Carburetor stripped, cleaned and rebuilt with carb repair kit. It has a fixed high-speed jet, which I had not encountered before. I tightened this back in to match how it was set before, gently seating, same amount of thread showing.
New fuel lines and OE filter.
Lower unit dropped, new impellor, new drive-shaft seal, and change of gear oil.
After all this and an embarrassing mix-up of the HT leads.....she fired up and ran great in the tank. Adjusted the low speed jet as per manual, gently seat and then back out 1 3/4 turns. It ran happily like this, so I left it. I didn't drop the revs, lean out etc, as I wasn't sure of the procedure for a fixed jet carb, and it seemed happy enough.
Now to the problem, on the maiden sea trial! Again the motor fired up great and propelled two of us happily along in a 60's Mirror dinghy, happy at lower revs. Raising the revs didn't do much apart from produce a lot more smoke, the boat was heavy, too much load for the motor I think so we kept the revs lower. I also noticed that the engine sat quite low in the water, the exhaust holes (6 little ones) were frequently below the water level, but it seemed to be blowing out hot exhaust and a little hot water quite happily. After a short while, 10 minutes or so, we noticed that the revs were audibly starting to drop, slowly. after perhaps another minute or so, the revs had dropped sufficiently to stall the motor. There was no hesitancy, no back-firing, no rough running no mis-firing to suggest running on one cylinder or an electrical problem. After a few pulls of the starter she would eventually fire up again, and then run happily as if nothing had happened! Until the whole procedure occurred again.
I would really appreciate any opinions on the likely cause of this gradual loss of revs/power, and then why it would run happily again shortly after? If it was too rich I wouldn't expect it to fire up again so soon without plugs being cleaned?
Potential causes I have considered:
1. The fuel shut-off switch below the tank was not cleaned or inspected, could this be causing fuel flow problems, or a vacuum? Filter appeared to have fuel in it, although never full. Sometimes wriggling the fuel hose would produce more fuel in the filter.
2. Turning the motor left-right seemed to speed up the rev decline, could this point to fuel flow issue?
3. She might be running hot, the cylinder head was very hot to the touch. There is not a great deal of water flow out the exhaust, although I am led to believe this is normal?
My plan currently is to strip and inspect the fuel cut-off, assuming this is possible and not just a part to replace. I would appreciate the procedure for tuning carbs with a fixed high-speed jet, so I can make sure I am doing it correctly.
Any advice much appreciated!
Thanks,
Edd (London, England) and Hugo (Exeter, Devon, England)
I have recently restored to life my friend's 1979/80 Evinrude 4HP, which he inherited from his Grandfather. It is a European model no: 49B36D, which Dan Gano (who supplied the parts) identified as a 1979 motor (4904/4932/4933) but with the points ignition from 1980/81, the E-4 models. The motor had not run for many years, the following was inspected and serviced before attempting to fire her up:
Flywheel pulled, ignition parts inspected. All looked brand new, even the coils. Points set to .020. HT leads, caps and spark plugs replaced. Spark tested and looked good.
Carburetor stripped, cleaned and rebuilt with carb repair kit. It has a fixed high-speed jet, which I had not encountered before. I tightened this back in to match how it was set before, gently seating, same amount of thread showing.
New fuel lines and OE filter.
Lower unit dropped, new impellor, new drive-shaft seal, and change of gear oil.
After all this and an embarrassing mix-up of the HT leads.....she fired up and ran great in the tank. Adjusted the low speed jet as per manual, gently seat and then back out 1 3/4 turns. It ran happily like this, so I left it. I didn't drop the revs, lean out etc, as I wasn't sure of the procedure for a fixed jet carb, and it seemed happy enough.
Now to the problem, on the maiden sea trial! Again the motor fired up great and propelled two of us happily along in a 60's Mirror dinghy, happy at lower revs. Raising the revs didn't do much apart from produce a lot more smoke, the boat was heavy, too much load for the motor I think so we kept the revs lower. I also noticed that the engine sat quite low in the water, the exhaust holes (6 little ones) were frequently below the water level, but it seemed to be blowing out hot exhaust and a little hot water quite happily. After a short while, 10 minutes or so, we noticed that the revs were audibly starting to drop, slowly. after perhaps another minute or so, the revs had dropped sufficiently to stall the motor. There was no hesitancy, no back-firing, no rough running no mis-firing to suggest running on one cylinder or an electrical problem. After a few pulls of the starter she would eventually fire up again, and then run happily as if nothing had happened! Until the whole procedure occurred again.
I would really appreciate any opinions on the likely cause of this gradual loss of revs/power, and then why it would run happily again shortly after? If it was too rich I wouldn't expect it to fire up again so soon without plugs being cleaned?
Potential causes I have considered:
1. The fuel shut-off switch below the tank was not cleaned or inspected, could this be causing fuel flow problems, or a vacuum? Filter appeared to have fuel in it, although never full. Sometimes wriggling the fuel hose would produce more fuel in the filter.
2. Turning the motor left-right seemed to speed up the rev decline, could this point to fuel flow issue?
3. She might be running hot, the cylinder head was very hot to the touch. There is not a great deal of water flow out the exhaust, although I am led to believe this is normal?
My plan currently is to strip and inspect the fuel cut-off, assuming this is possible and not just a part to replace. I would appreciate the procedure for tuning carbs with a fixed high-speed jet, so I can make sure I am doing it correctly.
Any advice much appreciated!
Thanks,
Edd (London, England) and Hugo (Exeter, Devon, England)