What You Need To Know About Mercury Optimax's! | Troubleshooting

What You Need To Know About Mercury Optimax's! | Troubleshooting

There are a couple of basic tests and procedures that a lot of people skip over when trying to troubleshoot a Mercury Optimax. Here is a short video that goes over the basics which should get you pointed in the right direction.

Starting with splitting the chaps to make life so much easier, then doing a spark and compression test. Optimax’s are known for failing coils. So a spark test will show you if this is one of the problems.

**** IMPORTANT!!!!!******


Checking the air and fuel pressure on an Optimax next is super important to properly diagnosing the issue. If the air pressure is not where it should be the fuel pressure will not build either.

Sometimes people can chase fuel pressure without even fixing the air pressure and waste many hours fixing something that wasn’t broken.

Most Opti’s require 90 PSI fuel and 80 PSI air. If these pressures are off, then start with the air pressure and check the compressor by clamping off the air dump hose on the PORT fuel rail. The pressure should spike, then check the fuel as well.

These tests can get you up and running way faster then anything else. Usually a spark plug, ignition coil, or some dirty fuel filters are what the problem is with an Optimax!

****Disclaimer**** This video is just a visual aid for locations and parts of a normal service.

Enjoy the Video! Thanks for watching and don’t forget to like and subscribe!
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Douglas S says:

Some call them optipop by nerds who think they can rev till they pop. I usually run low 5000 at the most never have a problem. Think 5600 is maxed 6000 they will fly apart. Mercruiser 140 was 3500 and 4000 and up to 5000 blew them up.

Douglas S says:

I run 2 filter traps for fuel and one on the engine very seldom have fuel issues. Still get shitty fuel sometimes the primary filters save me and got me back home.

TheSanchezVideo says:

Great info!!! Quick question, where does the fuel line go to on the exterior VST pump? The barb on the front or the bottom? I rebuilt that pump and cleaned out the VST, both high and low pumps are working but at WOT the engine runs for 15-20 seconds and then drop as if the VST is low on gas and revs up and down. I think I might have gas and vacuum hose swapped.

John Pike says:

But…on the very Off Chance that your engine is Still Under warranty, and you want that pricey part "Cost Covered", Telling the Guy in the Office "you watched a video and did the diagnosis all by yourself? could vacate.
If u bought the engine "Used" from an add (not a dealer) research or ask what the warranty situation is.
But rest assured, if you bought your merc off of Barney Rubble, nix on the warranty…
boat safe/have FUN.

Rick Jones says:

I have a 150 op what should the water pressure be it pumping water fine slow down in a no wake zone the high temp alarm goes off.

revenge69ful says:

So if I live in an area that only sells 10% ethanol fuel I should stead away from this engine
Or would adding stabilized make it safe? Thanks so much

revenge69ful says:

Where are you located ? Lol
I might need you

Jason Custer says:

Great Info. any suggestion on where to start to repair a very sluggish take off / plane 2014 Merc 300 opti DFI ?
it runs great once it gets going

Kristie Vanthul says:

Where do I get that manifold for air over fuel,and can it be modified to also test low pressure over air

Kristie Vanthul says:

If I could I would offer an idea you should start a service called mechanic in a bottle 9.99 service.ill be customer number one

Nick Jarman says:

What is your opinion on the 1997 Mercury 135hp v6 offshore edition. Which I believe is the same engine as this one.

DEE TEE says:

Great video. What would you suggest checking if the option doesn't idle while cold? Once mine warms up its great. But until it warms up to about 125 it won't idle. Thank you

Sotharith Mom says:

Can I replace the air compressor on my own?

Southern Specialties Offroad says:

Motor runs great when you go past idle but at idle it’s wants to kill and runs rough motor has 85 hr on it and had been sitting for 5 months before I got it sometimes it’s kills more than others 2008 150 opti previous owner changed all 6 coil packs

Oliver Hawley says:

I have 2011 optimax 250 hp. Went out one day everything was fine until got back to dock and shut it off and went back to turn on but won't start. It cranks but won't start. Ignition 20 amp fuse blows everytime ignition switch is turned to the on position. Any ideas?

Gordon Mohr says:

what I learned: stay away from optimax

Jacob red white and blue nation says:

Motor looks like a piece of junk

Brian 3.2 says:

Thank you for this great video. I have a 2007 90hp that will bog down and surge at 3k rpms. No alarms are sounding. I changed th fuel filter and cleaned the vst. Any advice is greatly appreciated.

Joseph Schilcher says:

I think I am missing some bolts between the intake and the block? I was looking for oil leaks and spring carb cleaner and when I spray near the holes it reves way up… any ideas.

Dan Huynh says:

hi there! love your video =), also i was wondering if theres any thermostats on mercury 225 optimax 2005 ? if yes can you show me where are they located? im having overheating issued, replace water pump, but problem still remained it only happen when motor is idling and run on ear muff, pee hole wont pee, but when i used the top water hose i can see it pee from the pee hole please help , so my next step would be thermostats , not sure if thats the right things to do but im running out of ideas =(…

Christina Park says:

Have a 115 optimax that ran fine until we swapped out pedestal, originally thought a wiring issue, took to marine shop and learned fuel pump was bad
We ordered one and replaced, it did start and run for approx 3min. Then stopped. Noticed then the fuel pump had reverse polarity from the original. Suggestions? Now it wont even turn over, but we did swap the wiring to match polarity now. Would this have done damage? What should we check next?

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