225 Optimax dropping rpm's

[jeffrey.bean]

Hello all,

Yesterday I was out on my 23' Pro-Line WA, ( bought it this past Sept.) it's powered by a 2003 225 Optimax with approx 650 hrs. At about 4500 rpm's it would drop 20-30 rpms for a second or two, then jump back up with out me touching the throttle. It would do this at random, I dropped down to 4100 rpm's and didnt experience the problem.

I just replaced the fuel filter/ water seperator, I havent replaced the in-line filters yet.

I have a 140 gal fuel tank that had 90 gal.( told it was treated) in it when I purchased the boat. I have since added 55 gal to the tank with quickleen and startron. I was told the 90 gal was put in this past spring.

I plan on changing the in-line filters this week, any other ideas?

Thanks,
Jeff

[master wrench]

Hello Jeff,
You could have a number of problems causing the issue you are having. One could be you have a bad plug wire and is arching when voltage goes up. A bad direct injector could be going bad, or a fuel injector. If you have the older grey colored fuel hose feeding your engine and its never been replaced in the past few years, that could be a problem. Todays fuel with Ethynol is eating the inner liner out of the older grey lines and causing the lines to collapse internally causing a fuel restriction. Has the diaphram pump ever been replaced or rebuilt on the engine?

As you can see many items could be your issue. If you need further help figuring your problem out feel free to give me a call at the shop.

Good luck and safe boating!

[jeffrey.bean]

Thanks for the reply John, a guy on another forum said he had the same problem with the same motor, turned out to be a plug wire. I'll have to check them when the weather breaks.
Not sure about the diaphram pump, the boat was bought through a broker so I never had a chance to speak with the owner.

I appreciate all the info, it gives me a place to start. If I cant figure it out, I'll be in touch.

Thanks....

[cisco651]

Having owned a 225DFI OPTI...

The first thing I would do is to REPLACE the gas in your tank!!!
Merc will tell you that gas stored in the tank for nearly 90 days will "Phase"... that is the gas will seperate...adding new gas will only contaminate the new gas...

Before you go and spend a ton of money, and I know you don't want to hear it, drain your old gas first...add new gas...run the boat...see if problem goes away...my performance problem, like yours, did...

Don't put anymore gas than you will use within 30 days in the tank...(Mecr reccomends)
Make sure you have Iridium Plugs installed (prevents carb build up per Merc).

Go to auto parts store:
buy 25' gas line
1 high volume gas pump (around $135)
30' wire (to feed gas pump)
2 clips for battery connection

Cut 5' off of gas line (the IN side of gas pump) attach the other 20' to the OUT side of gas pump/connect the 12Volt cable to the gas pump/connect the clips to the end of the cable.

find an attachment where you can DRAW the gas out of your tank/ don't use gas fill...
using the fuel line as a feed line will demonstrate whether or not you have a restriction in your feed line or not/may have problem with anti-syphion valve (remove it)/may have issue with parcial blocked pick-up tube/

So Much more>>>Just replace your fuel first>>>save yourself same time and money...

Bruce