help with Evinrude 25 please

I have a 1989 Evinrude 25 hp long shaft with remote controls. I was wondering if anyone with one of these can confirm if these conditions are normal. First, the motor idles nice, revs quickly, great acceleration, and has great top end power. When not on a plane at low rpm, around 2500 or less, I get a little sputtering and roughness after running at this speed for a while. Is this kind of a 2 stroke thing or should it be smooth over all rpm ranges? I've been on bass boats with 150 hp 2 stroke motors that seem to run rough at lower speeds as well. I wasn't sure if that was normal or not. Secondly, what temp should this motor operate at? I have a temp gauge and it varies between 145 and approximately 160. The gauge has marks at 130, 145, and 170, I believe. The sending unit measures cylinder head temp, not water temp. The SLOW system is not engaging, I was just wondering if this is an okay temp. The motor has new rings and all new gaskets and seals, new fuel pump, carb rebuilt, float set with OMC gauge, timing and carb synced, new water pump and thermostat. Spark plugs are clean with no buildup, same with the tops of both pistons, so it seems to be firing on both cylinders. Thanks for the help. I'm kind of new to outboards and trying to learn as I go.

Nohassalkindaguy,

What KIND of gasoline are you using?
Does it contain ethanol?
(Virtually NONE of the older 2-cycle outboard motors run well, at all RPM ranges, with ANY alcohol in the fuel.)

Changing to PURE GAS, with the proper amount of QUALITY 2-cycle oil, will likely fix your problem in 1-2 tanks, provided that the alcohol in the gas hasn't deteriorated the inside of the gas line & "made a mess".
(Just in case, I would also change the "onboard" fuel lines, replace the sparkplug wires & clean the tank out THROUGHLY.)

yours, satx

Well, you probably know as much as I do about motors. The temp thing you are mentioning is normal IMO, thermostat opens at 145 deg.
Cannot help with the rough mid range running thing.
Tim

Thanks for the help. My fuel tank is new, it has only had 91 octane ethanol-free fuel in it. I use lucas 2 stroke oil at 50:1. I may take the advice and replace the hoses and plug wires.