1991-70hp rude surges when cold

[patrick4266]

My 1991-70hp rude surges when cold. It will run fine to about 4000 rpm and then starts surging. After 5 or 10 minutes it runs fine. I think 5 or 10 minutes is too long to warm up. It has a brand new thermostat.

 

[jtexas]

Re: 1991-70hp rude surges when cold

Has the warm-up time been getting longer since you bought the motor? What's the surface temp where you're boating?

You did replace the poppet valve springs along with the thermostat, right?

Did the new thermostat reduce the warm-up time at all?

My opinion, not much difference between 5 minutes & 10 if you're waiting for your plane to push back from the gate, but huge difference if you're waiting for an outboard to warm up. Ten minutes is too long for sure, 2-3 minutes sound about right? 5 minutes...not much longer.............