Starts right up sometimes, but other times crank no start

[JeepGuy319]

Hi everyone,
I am new to boats and 2 stroke motors, but I do have mechanical experience working on cars and small engines. Anyway, I have a 1984 StarCraft with the 70 horsepower Evinrude 2-stroke. When I start it, I push the key in to activate the primer solenoid, and it seems to work sometimes, but half the time, it will crank forever until the battery drains. It cranks fast enough, and it runs great when it is warm. I am not sure what to do or where to start. It is a recent purchase, so I ran it last season but have not replaced any fuel or ignition system components yet. Does anyone know what could be causing this issue? The bulb on the fuel hose does not hold as much pressure as I think it should.

 

[racerone]

Do you hold the key pressed in while cranking it over ?--Have you tested operation of the electric primer valve ?-----The bulb is a manual fuel pump.----Only used to fill carburetors.----Once motor has been cranked or run , the bulb does NOT need to be hard.-----Start with posting the actual compression values.----Load test the battery.-----Does spark jump a gap of 3/8" on each lead ?----Take starter apart for inspection / cleaning / ohm check on armature and perhaps new brushes.

 

[JeepGuy319]

Do you hold the key pressed in while cranking it over ?--Have you tested operation of the electric primer valve ?-----The bulb is a manual fuel pump.----Only used to fill carburetors.----Once motor has been cranked or run , the bulb does NOT need to be hard.-----Start with posting the actual compression values.----Load test the battery.-----Does spark jump a gap of 3/8" on each lead ?----Take starter apart for inspection / cleaning / ohm check on armature and perhaps new brushes.

Yes, I hold the key the whole time. I am not sure how to test the electric primer valve. That is what I thought it was initially, but I still hear a click most of the time. How would I go about testing that? The starter is fine, it cranks over as fast as it should. It makes 90-100 PSI of compression. Battery is old but like I said it still cranks over fine. I will replace plugs and wires soon.

I will also add that it gets terrible gas mileage, at medium to 3/4 throttle, it burns 3 gallons of fuel within 10 minutes.

 

[racerone]

Compression should be about 140 PSI on that motor.----Is red lever in correct position on the primer valve ?----Sounds like the float valves in carburetors need attention.-----Or fuel pump diaphragm is ruptured.----Here I would retest compression or pull the head to check cylinder walls for scoring.----Mixing gas / oil at 50:1 ?

 

[JeepGuy319]

I will re-test compression when I get a chance. I do not have time to pull the head; it was just a cheap boat that I figured would last me 5 or so good seasons. I will look into the fuel pump diaphragm, I have not pulled the carb or anything yet. I mix the gas and oil correctly. Would you be willing to explain the red lever on the primer valve? Isn't that to manually bypass the solenoid?

 

[racerone]

I can not see or touch your motor !----The red lever should be inline with the valve body for normal operation.----If I saw 90 PSI here with my gauge the cylinder head would be off in a matter of minutes !

 

[JeepGuy319]

I can not see or touch your motor !----The red lever should be inline with the valve body for normal operation.----If I saw 90 PSI here with my gauge the cylinder head would be off in a matter of minutes !

I'll do another compression test when I get home. Thanks for the help, I am hoping it is a simple fix, but it almost never turns out to be like that lol.

 

[Crosbyman]

see video

 

[airshot]

You need to locate a " Factory Service Manual" not an aftermarket one. All your adjustments and specs will be there. When cranking over, are the plugs firing? When it refuses to start but cranking over are the plugs firing?
It does not sound like anything simple, so time to locate a service manual.
I owned a 1979 70 hp, great motor. Had it on a 18' Star craft bowrider. Used 6 gallons in slightly less than one hour at wot. Idled great, only issue was a bad CDI box, in my 7 yrs of ownership.

 

[Crosbyman]

fwiw... my old 4 cyl Merc 50 would burn 6 US. gal/Hr wot... so
a 6 gal in less than 1hr for airshot's 70 seems in the ballpark !

that said better fix yours....(3 gallons of fuel within 10 minutes ?) before the EPA jails you

 

[saltchuckmatt]

Yeah, carbs, fuel pump....powerhead could be toast, I buy those around my place (Seattle area) $200, sometimes less. Take the time to do a few inexpensive diagnostics, so someone like me doesn't come along... and makes $$$$.00

Easy and not much time.

 

[airshot]

Testing or guessing....which one costs more ??