1999 Johnson 150 H.P. problem

[Bro Bill]

Sometimes, not always, when first taking off motor shakes badley, and won't take off { like rev limiter working} If I shut down, trim all the way up for 15 seconds or so, go back down it will run just fine. Also hot light and horn go off for maybe 20 seconds once in a while then clear. New water pump and voltage regulator recently. Appreciate any help.
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[Chris1956]

That motor has the S.L.O.W. system, which kills spark to 1/2 the motor, when it detects an overheat. That sounds like your issue. Since the waterpump is new, it is likely a faulty overheat sensor or faulty thermostats. You might remove the 'stats and retest. If it gets better, replace the 'stats. You can test both the stats and overheat sensor in a pan of hot water on the stove, and a candy thermometer.