Surging new 150 Optimax

[oly67]

I have a new '09 Reata 1850 with a 150 Optimax. Sometimes(2-3 times) when I am out with it, rpms will surge up and down about 300 rpms. Very noticeable at low to mid speeds. It does have a power loss when I gun it at rest to get it to plane because of this flunctuation. Most of the time I have had it running, it runs well. I have had it to the dealer 2 times, and of course it does not do it then. They have checked it with their computer and have run it on the river and can not find anything wrong. I now have it back and I am going to dump a can of seafoam in it and hopefully get it back out on the water before it gets to cold here in Iowa. Any ideas what might be happening?

[yarcraft91]

Does your motor do this when warmed up? My 50 Merc EFI behaves that way at 750-1500 rpm from a cold start until the engine warms up. Seems like an engine management computer glitch or a sensor problem.

[oly67]

Yes, it does it when warm.

[ffishman]

If you are running a "vented" prop, try plugging the vents. Sometimes this will help.

[oly67]

Not running a vented prop.

[TomP.]

I have a 2000 135 Opti and mine at idle will sometimes speed up and slow down to the tune of 1000 rpms over normal idle. It is not a temp issue the guys in the shop don`t have a clue. When mine does it I shut it off and restart it and then it runs fine. Never sends a code and very very intermitent.

[staylor]

...can be caused by only a few items which are not that hard for a Merc mechanic to check. First, check and make sure the rig has a good battery rated at a minimum of 1000 marine cranking amps and that the connections at the battery are clean and tight. Also check under the cowl for any sign of a leaking fuel line or any loose connection in every fuel line running from the tank to the motor. Replace the fuel priming bulb if it isn't completely hard when the motor is running. Second, check the throttle cable and throttle cam roller adjustments- this includes carefully checking the throttle roller for flat spots from wear or an out of round condition. Third, check the throttle position sensor or just replace with a known good TPS. Fourth- replace the tracker valve and diaphram, and the fuel pressure regulator with ones known to be good. The dealer cannot inspect these last 2 items without special tools so its often easier to just swap in a good one. If all of the above doesn't fix it, then suspect a coil thats breaking doiwn under load. Years back my 150 Opti developed a slight suge while trolling- turned out to be a worn throttle roller. I think they cost something like $2. and snapped on and my dealer just gave it to me fro free. You do need a special tool to loosen the EPA approved tamperproof connection to adjust the roller after its snapped on- available from some auto parts stores if you ask enough times.
Doug