Mercury Optimax Question

[jfkal]

Planing to buy a boat with a Mercury Optimax 225 HP OB. Seems to run fine (most of the time). Running it a 5,000 rpm it randomly falls down to 4,500 rpm, then recovers tio 5,000 rpm and does the whole play again and again.
Fuel is good, filters replaced. Any ideas? Many thanks
Joerg

 

[QBhoy]

Hi. Trying to keep it simple. How’s the battery ? Plenty load taken by these things at full chat. Do you have smart craft ?

 

[QBhoy]

Also. You mention the fuel filter is fine. Is that a pre filter or the VTS. You might have both. Apologies if you have checked this. All the best.

 

[jfkal]

Battery good. No smart craft :-(. Not my boat yet. Simple trying to get ideas on what it could be and the cost to it.
Trying to eliminate any terminal illnesses ;-). Thanks

 

[jfkal]

Good point indeed. Not my boat yet. Simple trying to get ideas on what it could be and the cost to it.
Trying to eliminate any terminal illnesses ;-). Thanks

 

[QBhoy]

Understood.

Always a bugger when you can’t mess with it yourself. I’d doubt it’s anything serious to be honest. Might be tempted to use it as a money off bargaining proposal ?
Have a look on the US Iboats forum. They pretty good at these kind of things.
I only know the basics of these things having only had old school outboards previous to the most recent inboards. Currently have a merc mpi.

 

[jfkal]

Noted with thanks

 

[longjohnsilver]

Hi. Trying to keep it simple. How’s the battery ? Plenty load taken by these things at full chat. Do you have smart craft ?

Is that right? I'd expect the opposite, plenty of charge going into the battery.

 

[jfkal]

Are you suggesting that the alternator wakes up and goes to sleep to account for the drop in rpm?
Cheers
Joerg

 

[Hambleite]

We had a similar problem a few years ago on our previous 150hp Optimax. It turned out to be the HT leads, which was an easy and cheap fix.

I can't say this will cure your problem but it's worth a try.