Rough idle mercury 2000 225 optimax

[jaybird73]

Engine 2000 225 optimax. Model# 1225473wd Serial # OTO19488

New boat to me has 50 hours on motor but has been sitting for a long time. Compression checked at dealer was fine, they replaced high output fuel pump and all the hoses (Supposedly) Also replaced the ignition switch and checked all vent hoses in gas tank. New plugs but I had to re gap to correct (.032-.033) torqued down at 20#s. I have ran two tanks of gas through with mercury quickleen no ethanol in these two tanks. Runs great going down the lake to WOT but does seem a little slow out of the hole but again new boat to me. Starts right up with pumping the bulb hard prior to first start. Idles fair while in gear around 500 to 600 rpms. When in gear it has what I would best describe as a miss. It has never died and once over 1000 RPMS runs like a top. It runs the worse when I am done fishing have trolled into the dock turn it off then go get the truck. When I am putting the boat on the trailer is when I can really hear the (miss??) . After I re gapped the plugs it did run better and starts better but still has that miss at idle in gear. Voltage is 13.9 at idle but it does not have the correct battery in it so replacing that today.

[rocketman6965]

I had same motor and same problem. I'll bet you have at least one chipped reed. Stock reeds are stainless and can harm motor if they break and get in to cylinder. Even if not chipped, I would order a set of TDR reeds from Don. Don also suggested to open spark gap a little more for troubleshooting purposes. I believe it was .035.

[jaybird73]

Thanks man was thinking of doing that down the road but may have to do sooner than later.

[Savage]

I would verify that ALL of the fuel lines and primer bulb were replaced at the EXACT same time.

Click on this >>>>> Performance problems? Read Here and Upgrade Fuel Supply System FIRST!

[EuropeanAM]

I would verify that ALL of the fuel lines and primer bulb were replaced at the EXACT same time.

Click on this >>>>> Performance problems? Read Here and Upgrade Fuel Supply System FIRST!

+1... and try FRESH (new) spark plugs. They should be replaced every 364.99 days, anyway.

Recommended Annual Maintenance for Optimax Engines

[EuropeanAM]

i own this motor amd have had the same issue .
it eats plugs.. do them every season.. auto parts stores carry them and usually way less than my merc dealer.
.make sure thermostats are updated.. and not plugged if you idle through shallows or over sand bars they plug.. and idle won't be great. i also run dons mix minus the quick care.. i use quivkleen and prem plus in gas..noticeably better injector clicking with oil mixed 150:1.

also check director injectors..u want to see blue not black injectors under fuel rails.. the black ones had a much higher failure rate.

also check and lube throttlle roller above vst. mine was egg shaped so idle was never idle and caused problems . i replaced roller and now every time i release throttle it rests in same spot.

hope this helps

ONE engine per thread, please.

Plugs are an ANNUAL Maintenance Item (SHOULD be replaced Annually). That's NORMAL.

At this stage of the game- any engine with more than 50 hours on Black Direct Injectors should be just FINE. The problem that existed there would have shown up a LONG time ago (and the black ones actually have a slightly lower failure rate in terms of validation testing and flow rate).

Just an FYI.

[jaybird73]

Thanks guys for all the great information. Engine is at a certified mercury mechanic. Engine checked out for compression and everything else major. He is going to check thermostats and rebuild manual fuel pump. Hope it is a quick fix but of course when he water tested it did not think the idle was to bad

[jaybird73]

Ok so got the motor back. The engine runs great going down the lake and idles good when I first start it. It is a little slow out of the hole but also mid 80s water temperature 90 plus degrees outside and really full tournament boat. Last night it died twice when we where switching spots when I put it in gear. The second time the engine light came on but when I put it neutral and got above 1000 rpms went off. Night tournament so ran around 35 back to boat ramp. Idle was really rough loading the boat. Two different mechanics have said motor is great. Will get codes read next week but getting a little frustrated and pocket book getting a little light.

[EuropeanAM]

Just a hunch:

Make sure the throttle is ALL THE WAY at the idle position (NO throttle applied at all) when turning key on and when starting.

The ONLY time throttle should be applied is when IN GEAR, and going somewhere.

[jaybird73]

Ok thanks for the response. I am a little confused by your response. The gear shift is always straight up and down when I start the engine. The issue was when I put it in gear the engine died and engine light came on with no alarm. When I started the engine the second time the light was still on so I put the engine in neutral and slowly got RPMs to 1000. At that time light went out. After doing some reading today at lunch learned the big no no for throttle in idle with this engine. Have two boats and owned boats for 20 years and have not had one act like this.

[EuropeanAM]

Also should check throttle cable and make sure it's consistently returning throttle against the idle stop (not pre-loaded, but consistently on the stop).

The "technical" tension for HAND CONTROL throttle is to place a piece of notebook paper in the stop. It should hold the paper... but you should be able to pull the paper out without tearing.

How's that for technical?

[jaybird73]

Funny very technical:). Will check that out. I have a short video of the issue will try to figure out how to load. Thank you for your help.