2003 johnson 70hp 4 stroke loss of power

[Robert Kemp]

This is a new to me boat. I've had it since May and it has always started fine, idled fine and ran fine. Last weekend, with a very full boat running at full throttle, it would drop from 5500 rpm's to 4500 rpm's with a detectable sound change like it had dropped from 3 cylinders to 2 then back up to 3 after about 7 seconds and only at full throttle. There has been a check engine light on since 15 minutes after the previous owner delivered it but never noticed anything wrong in performance until last weekend. Does anyone have any ideas if this is a common problem or any thoughts on the cause? I'm tempted to just keep using it until I pull it for the season in September then just take it in and have it looked at. Thanks

 

[racerone]

It is a 4 cylinder 4 stroke built by Suzuki.-----Checked for water in the fuel ?

 

[jakedaawg]

What code is it flashing before the check engine light comes on solid? I.e. 3-1. Would be 3 quick flashes then a slight pause and then 1 quick flash.

 

[Robert Kemp]

Thanks for replying.

Fuel is all fresh so I doubt it has water in it and it also runs fine in every other throttle position.

The code says something about engine temperature but has always been on but never any performance problems. The actual temperature gauge is always normal.