Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

So, basically I am new to any kind of engine repair. I fear I need a new starter however here goes my problem.

Last year the boat was fantastic. Got the boat winterized by a dealer, and now it isn't so fantastic. The first problem we have is that the boat will crank first turn of the key without a problem, and it runs like it is brand new out of the box 2006. Other times and this is the norm I have to turn the key 5 or six times before it will turn over, then still runs great. After some listening with the cover up I notice that I hear a whirring sound for about 10 seconds then it stops and nothing happens. I turn the key again and I hear a click and no whirring. Turn the key again "click", again "click", then again "vrroooom" starts up great. I really don't want to buy a new starter but if that is the problem then that is the problem.

On to problem two. In neutral the boat decides to stall, this is new this year also. I figured that it was just a break in thing after winterizing. Seems like it is the norm now. The engine runs great otherwise, just won't start and will stall at idle which in turn makes me have to go through the starting problem again.:facepalm:

Help, Please.

Re: Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

Hi, and welcome
For problem #1 check all battery/starter connections (including ground) - make sure they are clean and tight. Also check battery voltage - should be 12.6+volts.

For problem #2 you'll have to provide more info before someone can help. What year engine? Serial # will be helpful.
Edit - just noticed it's a 2006?

Re: Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

Another retired guy said:

Hi, and welcome
For problem #1 check all battery/starter connections (including ground) - make sure they are clean and tight. Also check battery voltage - should be 12.6+volts.

For problem #2 you'll have to provide more info before someone can help. What year engine? Serial # will be helpful.
Edit - just noticed it's a 2006?

Click to expand...

Problem #1, I went through all the connections and checked for cleanliness along with tightness, and I went through with a voltmeter to see what is going on everywhere and everything is good. I was out in the boat today and it started right up, checked the charge gauge and it shows that it is charging at idle around 13 to 14 volts...under full speed it looks to be charging the full 14 volts. (seems high at idle?) It never goes into the "danger" zone however so I am somewhat confident with it. So after this diagnosing I went for a little swim, got back in and had to hold the key down for 6 seconds before the boat got up the ambition to do anything. The only way I can describe it is like the boat needs to charge a capacitor before it will go and start up, I don't know if that is a good analogy but that is all I got.

Problem #2, I will have to go out and look again but I am 98% sure it is a 2006 4.3 MPI Merc. Could there be water in the gas? Like I said before though, it really runs great under load and goes fricking fast.

Re: Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

Re problem 1. Did you check the battery voltage at the terminals? Should be 12.6 or more. The fact that your voltmeter is showing a 14v charge tells me that either the battery is not fully charged, or it's not accepting a charge. If battery voltage falls much below 12.4 you will experience cranking problems.

Re: Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

If you are getting just a click and the engine isn't turning over or the starter engaging, then you either have poor connections somewhere, intermittent slave solenoid or intermittent starter solenoid.

Test it like this when it's not working.

View attachment Troubleshooting a mercruiser Starting system rev3.pdf

Re: Mercruiser MPI 4.3 sometimes cranks on first turn of the key and other times not

I was out on my buddies boat last week and he has been having the same problem. Ran great first day and then second day, no go. after going through some basic tests with the multimeter, I knocked the solenoid with a wrench WHILE he had the key turned. Engine started right up. Your problem definitely sounds like a solenoid to me.

I noticed on my '81 350 Merc, I have two solenoids, and on my buddies 2k 4.3 Merc, he only had one. regardless if you have one or two, just lightly whack on both to see if one of them are going bad.