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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4728
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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2001 70HP 4stroke fuel injected outboard wont start. pulled

Customer Question

2001 70HP 4stroke fuel injected johnson outboard wont start. pulled a plug to check for spark, there was. What caught me off guard was that the engine started and ran?
Submitted: 1 year ago.
Category: Boat
Customer: replied 1 year ago.
I would like to know what to trouble shoot next?
Expert:  Jeff G. replied 1 year ago.

Is the engine running OK now or what?

Customer: replied 1 year ago.
no, when I replace the plug i removed to check for spark it will not start.
Customer: replied 1 year ago.
I repeated this sequence twice with the same results.
Expert:  Jeff G. replied 1 year ago.

Is the engine turning over fast?

Put a voltmeter on the battery and see what the reading is, then while cranking. It's possible a weak battery is not putting out enough voltage to start the engine. Your engine uses battery voltage. Try this and post back the figures.

Customer: replied 1 year ago.
engine is turning over normal. was on a lake, stopped and was never able to get it going again. Engine had been a little hard to start last four times out but only initially, after that no problems. I'll get the battery voltage reading.
Expert:  Jeff G. replied 1 year ago.

What did the spark plugs look like? Black?

Customer: replied 1 year ago.
voltage 12.2 then dropped to 11.9 while cranking. I looked at two of the four plugs. And Yes they were moderately fouled. I will replace them all tomorrow.
Customer: replied 1 year ago.
also curious why it would s on three cylinders but not four?
Customer: replied 1 year ago.
would start on
Expert:  Jeff G. replied 1 year ago.

Could be the engine isn't turning over fast enough. With one plug out there is no compression and the engine cranks faster bringing in the proper air/fuel and spark.

Charge the battery as well.

Customer: replied 1 year ago.
Thanks, ***** ***** you know the results tomorrow.
Expert:  Jeff G. replied 1 year ago.


Customer: replied 1 year ago.
changed the plugs, did not charge the battery yet. Engine starts easily now. So if this is all because of fouled plugs is there still another issue to correct? Why were the plugs fouled? I have only owned the boat for 10 months, so I don't know how long ago the plugs were changed. Also, I do like to run the boat at slow speeds. I have seen posts relative to 2 stroke engines fouling plugs if ran at a slow speed for long periods of time. Thanks
Expert:  Jeff G. replied 1 year ago.

It's true long idle times can help cause fouled plugs in any engine 2 or 4 stroke. A engine running too cold can do the same. What I would recommend if you are idling a lot is to run a carbon cleaner such as Yamaha's Ring Free or Mercury's Quickleen in the fuel. These products will help stop or reduce fouling.

Make sure your thermostat is in place and operating properly, use a good quality, fresh fuel, of a Top Tier manufacturer. Use a marine 4 stroke outboard oil. All will help.