1985 Yamaha 70hp ETLK spark Plugs

[klietz]

I have just purchased a 1985 yamaha 70hp ETLK. Engine runs good but does at times of 3/4 or higher throttle surge. Only does it sparatically. I am changing the engine fuel filter, the fuel line, the in-line fuel filter, and the bulb. Went to change the spark plugs but when pulled the plugs all were different types and numbers?? Can anyone tell me what the recommended spark plug type and number along with the gap setting.

Thanks

[boats.net]

The spark plugs are number 33 in this diagram, set gap at 1 mm Yamaha Outboard Parts 1985 70ETLK CYLINDER CRANKCASE Diagram