Name:	rdfarr -	Reply
Subject:	225 Merc OB surging
Date:	10/30/2014 7:28:02 AM

Had a long run with my 225 OB before taking the boat out for the winter.  It was surging real bad, running smoothly for a few minutes but then dropping down few hundred rpm for a bit, then jumping back up to the higher rpm. This started happening toward the end of the boating season, and got progressively worse. Boat is out of the water now until next year. 

Question: Is this something I could easily fix, or do I need a mechanic?  If the latter, who in the Dadeville vicinity should I take it to? 

Thanks for any suggestions. 

Name:	CAT BOAT -	Reply
Subject:	225 Merc OB surging
Date:	10/30/2014 8:07:47 AM

Questions...  What brand OB is it?  Also, is it fuel injected?  A model would help as well.  (Yamaha HPDI, Merc Optimax, etc.)  Is it two or four stroke? 

Respectfully,

Steve

Name:	rdfarr -	Reply
Subject:	225 Merc OB surging
Date:	10/30/2014 8:43:11 AM

Sorry. I should have been more specific. 

It's a Mercury Optimax 225, fuel injected, about 2005 vintage, mated with a 23' cuddy cabin.  Was told that the injectors were rebuilt within the last year before I got it.  I've had the boat/engine since about May this year.  Don't know the number of hours, but was used infrequently in the Gulf before I bought it.  I've been careful to use only fresh regular gas, and including STA-BIL and enzyme fuel treatment.  

Name:	CAT BOAT -	Reply
Subject:	225 Merc OB surging
Date:	10/30/2014 3:43:52 PM (updated 10/30/2014 4:00:01 PM)

Merc Optimax is my favorite engine.  They are intesting machines.  They are both fuel injected and air injected engines.  Your problem is most likely on the FUEL side.  Optimax has a low pressure pump/lift pump and High Pressure fuel pump and they must be serviced properly.  Optimax is a DI (direct injection) engine, meaning the fuel/air mixture is injected directly into the cylinder while under compression.  Any drop in fuel pressure less than 38 psi AT THE HIGH PRESSURE PUMP will result in a lean condition/surge.  Do not operate the engine with this concern.  You will certainly damage the powerhead.  It is possible that the "Air Pump" (belt driven from the flywheel) is weak, or in need of service but not likely. Some early models were not serviceable.   If your previous shop/mechanic did proper maintanance and had the right equipment he would have done it already and then that prolly is not the trouble.   We have a computor program we run through the engine that will test the injectors and point out any problems and can certainly let you know what is wrong.  Another thing that may be causing the surge is the "high pressure pump screen" in the VST (Vapor Separation Tank) in the fuel system....  But, has it ever been serviced?  Mercury Optimax is a very complex engine.  They make a lot of power, sip fuel and still pass EPA standards as a 2 stroke.  Sorry for the long post/reply.  We will be happy to help you.  All that being said, the boat would need to be at our shop to diagnose and repair.  I am an hour away from you!!!  If you don't drive here, make sure you land at a Marine facility with the proper equipment and knowledge.  Also, there are a few other minor items that can cause your problems.

Respectfully,

Steve Northington

Cathouse Marine, LLC

334-358-2838

Name:	rdfarr -	Reply
Subject:	225 Merc OB surging
Date:	10/30/2014 6:06:07 PM

I don't know how the engine was maintained before I bought the boat. Looks like I need to bring it to you. Also have some critical rusty bolds to replace.

Will call for an appointment.  Wish you guys still had the facility on hwy 49.