Logo

1977 6HP EVINRUDE DIES AT HIGH SPEED

I don't think so.----Does primer bulb go hard ?-----Does motor run better with an assistant operating the manual fuel pump ?----Could be a weak fuel pump .-----The trouble shooting always starts with a compression test.----Post the numbers.-----You did replace the water pump impeller ?-----Test for spark that jumps a gap of 3/8" or more on both leads.-----Test spark with twist grip in idle.----And again at mid and full throttle.---Could be a broken wire from under flywheel to the CD unit.
 
All great suggestions. Question: Did the problem start at the beginning of the season? Then it could be a partially plugged high speed jet. It's located at base of carb, accessed through the front of the float bowl behind the hex cap screw.
 
Haven't used it in about 5 years. Replaced water pump, thermostat, plugs, rebuilt fuel pump, all fuel lines, primer bulb, runs great at low to mid rpm. High rpm runs about 5 mins and shuts down. Pumping water fine. Won't restart. Low compression both cyls - 65.
 
Those are wonderful motors.----Easy to repair and maintain.----The original head gasket tended to fail between the cylinders.---The new replacement SIERRA is about $20 and would be an easy fix.-----Or drop the motor of here, I can use another one for the grandson.
 
Those are wonderful motors.----Easy to repair and maintain.----The original head gasket tended to fail between the cylinders.---The new replacement SIERRA is about $20 and would be an easy fix.-----Or drop the motor of here, I can use another one for the grandson.
Much appreciated! I'll try it. Torque specs for head bolts?
 
Resurface head with 180 wet or dry, on a nice flat surface like heavy glass, or old section of countertop. Use figure 8 motion and reverse motion often. Lube and irrigate with soapy water. Install the cleaned bolt threads with LITE coating of anti seize. Put some on shank of bolts too. The original zinc coating has worn and deteriorated off of the bolt so that is why you have to replace it with a light coating of anti-seize. Don't try to pull that jet out from the float bowl unless you have a perfectly fitting screwdriver. Don't strip it out or you will be sorry. I have one ground for a perfect fit which I use. Don't forget to soak it down first with some JB 80 or similar product. Once the jet is extracted clean it out and make sure that the opening is fully cleaned to the correct size, use a welding tip cleaner with assorted sizes they are generally soft enough to clean the material without harming the jet itself. Even though the jet may look to be open, it may have a coating of debris that is limiting the fuel flow. Make sure that little donut gasket at the bottom of the vertical stem is making good contact with the float bowl, because any fuel that leaks by there is unmetered and will cause motor to run rich.
 
ORDERED HEAD GASKET. AFTER IT DIED AT HIGH RPM IT WILL STILL TURN OVER OK, BUT HASN'T RUN SINCE. WOULD HEAD GASKET CAUSE THAT?
 
Well.-----No body here can do the inspection for you.----Yes , if the original gasket failed it will stop the motor ------But is up to you to do some inspection.-----Could be a broken wire ----Bad sparkplug.----Failed CDI and running on one cylinder ETC , etc.
 
The head is warped so refinish it using flat glass and emery paper.-----Do this before installing the improved gasket.-----Post picture if old gasket is blown.
 
head gasket is blown right in the middle. head looks good. Great advise from you guys. Resurfacing head now. Let's see if it runs tomorrow!

image000000.jpg
 
MOTOR NOW STARTS UP AND RUNS FINE FOR ABOUT 15 MINUTES THEN DIES OUT. PUMPING PLENTY OF WATER. NEW THERM AND IMPELLER. CAN IGNITION PARTS HEAT UP LIKE CARS IN THE 70'S AND 80'S DID? COOLS FOR A BIT AND STARTS AGAIN
 
Put boat in the lake.-----Use a timing light on plug wires.------Run boat till motor fails / falters.----Observe the flashing light.----If light is not flashing steady you have ignition failure.-----Perhaps as simple as broken wires coming from under the flywheel to the powerpack.
 
Back
Top