I have a ’99 40hp 4 stroke on a Lund 1650 Explorer. The engine has had problems throttling up and down, wanting to die in the mid range. We got that fixed now it seems the idle is set really high. The question is what speed should I be trolling at at idle. Or is this more of a rpm discussion? Before I was able to troll at idle around 1.0-1.5mph now it’s around 2.5-3.0mph. Is there a standard rpm that these engines should be set at?
Any info. would be appreciated.
trolling speed will be determined by your prop. Yes there is an RPM range you should be idling at, I’m not sure what it is but I suspect it is around 600-750.
i believe your motor is a carbed motor they had some issues with these and need to be set with a vaccuum machine to balance them out if they guess and do it you will have what you are explaining happen the rpm should be 55o to 650 rpm if the vaccuum is nott set properly you compermise some where in the range you should have them set it down and you will be close to the speed you want
Merc service manual says idle speed for fuel injected motors is 750rpms +or- 25 rpms would think carb models would be similar.
Good info. everyone, thanks. 
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