2007 mercury optimax 75 hp hard or not starting

[acadian2022]

Good day all. I'm posting this for my Uncle that is having issue with his outboard. 2007 mercury optimax 75 hp it happens when I try to start it in spring at home before going to the lake talk to a buddy and told me to take the plugs out and put a little bit of fuel and then try it again and it started a week later I was going to the lake try to started at home started no problem got to the lake it wouldn't start try it again about a week at home no problem when to the lake did some throlling for about 30minutes and it stops after 45 minutes of paddling it started again that's pretty much what's happening me I think it's a fuel issue

 

[racerone]

Checked the belt driven compressor ?-----Check compression.-----Test spark.------Water pump impeller done every 5 years ?

 

[acadian2022]

Checked the belt driven compressor ?-----Check compression.-----Test spark.------Water pump impeller done every 5 years ?

Thank you for your reply. Here is my.Uncle reply: Morning spark is good so is the compression they change the water pump impeller so far that's all I know I might be talking to them today tks for the information

 

[QBhoy]

Hi. Thought I’d add…that in particular, the optimax (along with the modern 4 stroke efi) is highly dependent on its battery type and health. Anything less than the right and perfect health battery and they will struggle to fire up…just because the ignition and injection system needs to see the right level of available power (and cranking rpm) supplied to them…at the same time as the starter motor also demanding huge draw from the battery too. So common for the battery to be ruled out as the issue, just because it can turn the engine over apparently well. Be amazed at how common this is these days…the more and more modern and highly electrically dependant engines we see in recent years.

 

[acadian2022]

Hi. Thought I’d add…that in particular, the optimax (along with the modern 4 stroke efi) is highly dependent on its battery type and health. Anything less than the right and perfect health battery and they will struggle to fire up…just because the ignition and injection system needs to see the right level of available power (and cranking rpm) supplied to them…at the same time as the starter motor also demanding huge draw from the battery too. So common for the battery to be ruled out as the issue, just because it can turn the engine over apparently well. Be amazed at how common this is these days…the more and more modern and highly electrically dependant engines we see in recent years.

That you very much message passed on to my Uncle and have to say regardless if that is the cause this is very good information for all that is not aware as I was not...

 

[QBhoy]

That you very much message passed on to my Uncle and have to say regardless if that is the cause this is very good information for all that is not aware as I was not...

Yeah. Hope it helps. If not…good to know anyway. Honestly such a common thing these days. It’s caught me out before on both my mpi mercruiser and my efi merc. Very easy to think the battery is fine…just because it will turn the engine over pretty well and healthy sounding. Fact is…that there are so many sensors (in your case fuel pumps and compressor) and dependants that just get starved of power, because the cranking of the engine takes all the available from a less than perfect battery. These ancillary items just won’t even try unless they can get their required voltage. The injection system won’t even try unless it sees a certain rpm from cranking either, in some cases.

 

[acadian2022]

That you very much message passed on to my Uncle and have to say regardless if that is the cause this is very good information for all that is not aware as I was not...

Good morning all. Just a quick update from my Uncle as to what Mercury informed him will keep all updated in case one has the same issues: Morning here's the last update from mercury tech support they're saying it's the oil pump.