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upstart
22-04-2013, 08:30 PM
Hi Everyone,
A mate is having some problems starting his motor. It's an 80s vintage Johnson 70hp 2 Stroke. Does anyone have any ideas on what the problem could be? Thanks heaps in advance!

"Ok so the motor is a Johnson 70hp 2 stroke. On a cold start up the engine cranks slowly 3 or 4 times then speeds up and fires. After running out to an anchor spot and sitting for an hour or two it cranks quickly on the key but struggles to fire, sometimes causing flooding. It has a manual choke and I dont engage the choke unless it's the first start of the day. The battery is fully charged and holding charge fine. The spark plugs have just been changed, but the issue still happened on the old ones so I don't think it will be the spark gap."

Rip it up
22-04-2013, 09:25 PM
I'm no expert but does the fuel primer bubble get soft when sitting for a little while? Might be a simple fuel pump gasket leak etc. or a air leak on the fuel filter. Just some other ideas.

I also have two identical engines 80's vintage and have not had running since buying them 12 months ago.

Spaniard_King
22-04-2013, 09:40 PM
Cranking speed not up to scratch... starter motor needs overhaul of battery cranking voltage too low.. from several possibilities

upstart
23-04-2013, 08:13 AM
Would the dodgy starter motor affect the engine's ability to fire when hot?
Could it be a fuel pump issue?

Fed
23-04-2013, 09:18 AM
After sitting for an hour or two try treating it as a stone cold motor.

Slow cranking, test it to find the problem rather than throwing parts at it.

robsue
23-04-2013, 10:52 AM
Timing out.....my 60 merc was hard to start, had to get towed in twice, AND it had been serviced couple trips before, when bris yamaha checked it out for trade it was 10 degrees out

upstart
23-04-2013, 11:04 AM
Thanks for the replies so far. Gives us a starting point. (Pardon the pun) :)

FordGT
23-04-2013, 12:09 PM
As Fed said after an hour or so its a cold motor. I usually give one or two bulb primes and then choke for first couple of seconds of cranking. Usually does the trick.

honda900
23-04-2013, 04:39 PM
I had a very similiar issue on a johno 40, had the starter rebuilt did a bunch of other stuff to find out in the end the negative lead on the battery was full of the black cancer.. replaced the lead and away it went..

Regards
Honda