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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Mick i have a 70 hp 3 cyclinder johnson my problem is it

Customer Question

hi mick i have a 70 hp 3 cyclinder johnson my problem is it starts fine and idolls fine but when you put the trottel forward into gear its fine and starts to move off .now when i trottle up more the engine starts to jump around and vibrate till i trottle it back and it stops but is only doing about 5 knots would you have ever seen this problem before reards finnbarr
Submitted: 1 year ago.
Category: Boat
Expert:  Tan replied 1 year ago.
Hello. My name is ***** ***** like a possible ignition issue or maybe a bent prop shaft. To check for an ignition issue we need to use a timing light. Connect the timing light to the top cylinder. Run the boat watch the flash of the timing light. The flash should be steady with no dead spots. If no misfire move the timing light to the next cylinder. Continue till you have checked all cylinders. If you find a misfire swap that coil with a known good firing cylinder. If the misfire moves with the coil that coil is bad. If it stays we have another ignition failure. Which will require further testing. Tpo check for bent prop shaft or damaged prop spin the prop while watching the center of the proip shaft. If it wobbles there is the vibration. Post back with questions and findings.
Customer: replied 1 year ago.
I HAVE CHECKED THE PROP AND THAT LOOKS FINE SO AS YOU SAID I WILL HAVE TO CHECK COILS AND GET BACK TO YOU IN A FEW DAYS IF THATS OK TAN REGARDS FINNBARR
Expert:  Tan replied 1 year ago.
Ok Finnbarr that's fine. Let me know what you find.............Thanks.
Customer: replied 1 year ago.
HI TAN when the engine is out of gear and you rev it up with the choke switch next to the trottle it does not vibrate it is only when it is in gear ,and the presure is on to move forward up to the plane regards finnbarr
Expert:  Tan replied 1 year ago.
The engine won't act up without being under a load. That's why we have to do the test when the engine is acting up.

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