2000 4hp 4 Stroke not revving under load.

[psj]

Prop/shaft/plug/lead/compression all good.

Confirmed proper fuel and water flow.

Starts/idles perfectly. Revs fine in neutral but will only climb to 2150rpm under load so I'm turning to possible ignition issues and wondering if a spark tester will tell me the condition of the coil or is there a better test?

What is the next step(s) if the coil checks out?

Thanks.

 

[RCO]

I would be leaning towards the high speed jet in the carb being plugged up . The ignition system on that motor will usually either work or not. The low speed jet will supply enough fuel to rev it up in neutral and sound just fine . Can you get it to speed up by using the choke?

 

[psj]

No I can't. Choking kills it. I've even tried spraying fuel directly into the carb at WOT and all it did was flood the engine.

 

[psj]

Update: Picked up a tester and would only jump just shy of a 1/8" yellowish spark.