I took it into the shop late last year since it still is under warranty and they said they found air leaks in my fuel lines. They tighten several connections on the fuel lines and said a rep from Mercury told them that this could be my problem. It was late in the year and I didn't have a chance to take it out on a hot day to try it out again. I'm not sure if this fixed my problem. They also said on a hot day to run my blower all the time and when I pull into a cove let it idle for several minutes with the engine cover up before shutting it down. I don't know much about it, but there is a booster fuel pump that you can buy and have installed that is also suppose to be a fix for this problem. Mercury didn't want to install this booster fuel pump under warranty.
May 23, 2011 Rating
repairs by: Anonymous
so did you ever find out the problem. sounds like the problem i have.
Jul 25, 2010 Rating
2006 350 MPI by: Joe
When the weather is hot and the humid and I run my boat for about half an hour and then shut it down and try to restart it it won't start. I can hear the fuel pump running to bring the fuel pressure up and then I try to start it. After about 15-30 times of trying to start the engine it finally starts. Yesterday it took a good 15 minutes to start after running it about 15 at minutes. This happens every summer when it gets hot and humid. I have a friend that has a 05 305 MPI and this has happened to him also. He called a Merc Tech and they said they are aware of this problem and recommended some sort of higher pressure fuel pump to correct this problem with the high temps and humidity we have here in Missouri. This boat never sits out over night and sits in our basement garage so the fuel shouldn't have any water in it. Also I only use premium fuel and put stabilizer in every tank so the fuel should not be bad. This problems sounds like it is vapor locking to me. I will call the place where I bought the boat and see what they say about this. Any comments on my problem would be appreciated.
Jul 16, 2010 Rating
Mercruiser MPI Problems by: bajadawg
I am having nearly the same issue, My 05 Mercruise 350 magnum MPI with 555ECM is real hard to start when it is cold 70deg s. Calif.
I have to advance the throttle position and it cranks and cranks then starts but idle is slow and rough, i does clear out after a while and runs great the rest of the day, plenty of power and never stalls from forward to reverse!!
I have changed the S. plugs rotor & dist. cap, replaced the IAC motor, The MAP sensor, the coolant temp sensor and the prob still exist!
The worst part of this problem is if I shut the motor down while fishing in close to shore the motor is twice as hard to restart I have to pack ice from the cooler on the motor to cool it down before it will restart!!
Any sugestions?
PS two Merc factory techs cant find the problem 3 hours with computer scan tool!!!!!
Jan 04, 2009 Rating
RE: Problems with my Mercruiser 350 MAG MPI by: Anonymous
It appears the problem was related to a loose ECM (Electronic Control Module) connection. This problem was electrical in nature and had nothing to do with the fuel pumps or lines. Perhaps the engine cutoff as a result of the vibration at the higher RPM's that would cause the shorting in the ECM harness. I was told by the mechanic that reseating the ECM harness did the trick. No problems since.
Dec 30, 2008 Rating
Having the same problem. by: Anonymous
Hi,
I'm experiencing the same problem with my 2005 chaparal 260. Have you managed to resovlve the issue.
