2004 Mercury Optimax Help

[patbfishing123]

2004 225L OPTI
Serial #: 0T946547
Roughly 690 Hours

Last year I purchased a 2004 Triton TR 21X with a 2004 Mercury Optimax that has roughly 690 hours on it. A compression test was done at the time of purchase and all cylinders were reading 90 PSI. As soon as I got the boat, I had a new impeller put in and changed the lower unit oil. I ran the boat 6-7 times last year and it ran fine. The only issue I had with it was that it would top out at 63-64 mph and I couldn't get it over 5400 rpms. From what I've read, this motor should top out closer to 72-73 mph at 5800-5900 rpms. I was running a 26P Trophy prop and it was recommended that I go down to a 25P Tempest to get more rpms and see it that solves the problem. Before the winter, i took all batteries out and kept them inside, changed the lower unit oil, filled it up with non ethanol gas and then stored it in a garage.

Flash forward to this spring, I get the batteries back in the boat and get everything ready to go:

OUTING #1

First Run of the Day: When I get out on the water for the first time, I notice its a little hard to start, but I get it going. For the first run, it appears as though its running just as good as it did last year (but I never went over 4500 rpms because of rough water). I get to my first spot where I fish for 3 hours or so without starting the big motor.

Run #2: When it was finally time to move, the motor took even longer to start when I turned the key. It took me close to 30 seconds to get on plane (as compared to the normal 5-6 seconds), and once I got on plane it topped out at 4200 rpms. I ran 2 miles at 4200 rpms and stopped to fish for another half hour.

Run #3: Started it up again and this time could not get on plane, I couldn't get the motor over 2800 rpms. So I decided to fish a little longer and try again later.

Run #4: Started even harder this time and could not get it over 2000 rpms and it the rpms continued to decrease from there. Eventually the motor started running very rough and shaking. I used the trolling motor to get back to the launch.


After doing some research, I decided to have my cranking battery tested (I was running an AGM Intimidator). The cranking amps came back at 600 on a full charge, which I was told could be the issue since I need closer to 1000 for my motor. I purchased a group 31 blue top dual purpose battery since all my electronics/power poles are also being run off the cranking battery. I had the new battery installed and also had my reeds upgraded to fiberglass while it was in the shop.

OUTING #2

Run #1: Still seems to start kinda hard, and I heard a single beep alarm after the initial start, but once it got going it was good. I got on plane without a problem and again was able to run at 4500 rpms at 48 mphs (But again did not go any higher due to rough water). I fished for 1-2 hours after stopping.

Run #2-5: More hesitation when I turned the key, but eventually fired up. Just like last time, it took a while to get on plane and once I did, it only ran at 4200 rpms. And the rest of the day was very similar to my first outing. I'd hit the gas to the floor to get on plane and it ramped up fine like it wanted to go and would get up to 2000 rpms and stayed there.The rpms continued to go down as the day went on and eventually the motor started shaking and stalled out and would not start back up again. At one point i did forget to put it in gear and when I hit the gas, the rpms went up over 3000 and an alarm beeped (which I assume was just telling me that I didn't have it in gear). So it looks like I only have this issue when it is under a load?


What would cause this issue? It seemed like it ran fine on a fully charged battery each day, but then progressively got worse as the day went on. Any insight would be greatly appreciated!!

Thanks!

Pat

[JOE54]

charging system test please

[Savage]

Wow that's a novel!
Agree test charging system.

[patbfishing123]

I'm a little green in the troubleshooting game. What does a charging system test consist of? Thanks!

[Mon Mariner]

I sold a 04 Triton 21X 225 to somebody up that way a few years back. White/platinum gold stripe/dark gray seats. The max RPM's were 5750. I ran a 26" Fury 3 about 74 mph and a Trophy 4 26" 72 mph.

[EuropeanAM]

Agree- check voltage AT THE BATTERY with a DVOM while the engine is IDLING. The engine should have been running for at least 5 minutes. Report back with result.

Also need to know about the Maintenance History. Reference the FAQ Section for Recommended Maintenance.... for Optimax Engines.

Check the BASICS (Compression (currently), Spark Test, Fuel Quality/Delivery/Air-Fuel Pressures).

Check tensioner spring (70 lbs/in should "click" before end of travel).

[patbfishing123]

Thank you for you input guys. Finally got around to do some troubleshooting earlier this week.

I tested the charging system:

At the battery while the engine was off: 13.05 volts
At the battery while the engine was idling: 13.05 volts
At the battery while the engine was 3000 rpms: 14.52 volts

Seems to me like the alternator is working just fine?

I decided to let the motor run for 5 mins and test again, but i didn't even get to 5 mins. The motor was stuck at 1800 rpms and I couldn't get it to go back down to idle. After 3 mins of trying to get back down to idle, with no luck (tried screwing around with the hotfoot, thinking maybe it was stuck), a constant alarm came on. I turned off the motor and stopped working on it.

I consulted with a friend of mine who does motor work, he said that since the alarm was going off, I need to take it to a certified merc dealer to have it hooked up to the computer and diagnosed. So that's where I'm at, hoping to get it into the shop next week.

Pat

[patbfishing123]

Update on the motor after getting back from the mechanic:

First impression was that the engine was overheating and going into guardian mode.

He diagnosed fuel system, all good.

Diagnosed water pumps, all good.

Compression test, all cylinders had good pressure.

Checked thermostats, put a new one in just as a precaution.

Installed new impeller and gasket, old gasket was blown.

All this and no changes to problem. Runs well with muffs, but as soon as it is under a load, runs like crap.

He was looking around while lower was off and noticed a piece of the power head gasket sticking out. Turns out, the motor had power head replaced at some point and the gasket wasn’t installed correctly. He installed a new gasket and put everything back together. According to his test run, it ran fantastic with the new gasket. Something about the increased air pressure not allowing the water to get into the motor to cool it down, causing it to overheat and go into guardian mode.

Gonna take it out for a run on Sunday. Will report on results.

[Savage]

Update on the motor after getting back from the mechanic:

First impression was that the engine was overheating and going into guardian mode.

He diagnosed fuel system, all good.

Diagnosed water pumps, all good.?????

Compression test, all cylinders had good pressure.

Checked thermostats, put a new one in just as a precaution.

Installed new impeller and gasket, old gasket was blown.

All this and no changes to problem. Runs well with muffs, but as soon as it is under a load, runs like crap.

He was looking around while lower was off and noticed a piece of the power head gasket sticking out. Turns out, the motor had power head replaced at some point and the gasket wasn’t installed correctly. He installed a new gasket and put everything back together. According to his test run, it ran fantastic with the new gasket. Something about the increased air pressure not allowing the water to get into the motor to cool it down, causing it to overheat and go into guardian mode.

Gonna take it out for a run on Sunday. Will report on results.

Odd that the "water pumps, all good", yet a "new impeller and gasket" was installed due to "old gasket was blown".

[patbfishing123]

Savage, I’m very inexperienced with motors. What are your thoughts on this? Something with the water pump blew out the gasket?

[Savage]

Savage, I’m very inexperienced with motors. What are your thoughts on this? Something with the water pump blew out the gasket?

I'm sure everything will be fine, its the write up that didn't make sense.

Obviously the "water pumps" were NOT good, if impeller and gasket changes were required.

[patbfishing123]

Oh gotcha. I wrote that up from memory. Wasn’t verbatim from the mechanic. I could have gotten that part confused.

[patbfishing123]

I took it out for a test run yesterday and everything is exactly the same. No improvement in performance.

I started up the motor and let it run for 8-10 mins to warm up. 5 mins into warming up, a random single beep alarm went off. Is it possible that this alarm kicked it back into guardian mode? Also, when I took it to the mechanic (the first time), he said there were no codes showing on the computer when he plugged it in. Can it go into guardian mode without showing any codes?

[Bob G.]

I took it out for a test run yesterday and everything is exactly the same. No improvement in performance.

I started up the motor and let it run for 8-10 mins to warm up. 5 mins into warming up, a random single beep alarm went off. Is it possible that this alarm kicked it back into guardian mode? Also, when I took it to the mechanic (the first time), he said there were no codes showing on the computer when he plugged it in. Can it go into guardian mode without showing any codes?

If the motor went into guardian mode, there should be a Guardian fault code with parameters at that time. Also should be a Neutral Overspeed fault if you ran it to 3000 RPMs in neutral. I have done that a few times after I got a boat with a Hot Foot and it showed up in my diagnostics check.

If the motor is SmartCraft capable, I'd install a MercMonitor Level 1 so you can watch the idle and on plane temps and water pressure.

I'd also clean the compressor strainer just for good measure if it hasn't been done since you got the boat.

[Savage]

If the alarm sounded, then a FAULT CODE is set.....

[EuropeanAM]

Is this "mechanic" using the Mercury Computer Diagnostic System (or Mercury G3 System)? If so- get some PRINTOUTS of the RUN HISTORY and the FREEZE FRAME (Fault) History.

Totally separate- let's clear up something from your first post. This engine should NOT be turning more than 5750.

[rdmpsu]

I know this is is an old thread but I figured I would create an account and reply to it because it helped me and I hate unanswered questions.

I came to own this motor after what I can only assume happened when the OP sold it to someone who also tried to fix it and then that person sold it to me saying that it ran fine and it was just "too big for his boat". It looked like someone had rolled it down a gravel driveway at that point but compression checked out and for a couple grand I took the chance. Imagine my disappointment when I toss it on the boat, it fires up fine and the first time out it dies at 3k rpm and will not restart.

I'll save the long story and a couple months of research, googling the serial # which lead me to this post, reading a lot of stuff posted by Don and going borderline insane, I think I have it to where it needs to be (I've run 4-5 times w/o issue).

This thing had a bunch of what I would call red herrings that could have attributed to the problem but probably didn't cause it. The oil level sensor was bad so the alarm would go off similar to an overheat. The VST was having some funky deal with what I can only try and say was the check valve under the HP pump essentially allowing the low pressure to flow back into the reservoir ( this one took me a while because I tested both pumps, relay, float needle, pulse pump). Merc wanted like $800 for the whole seal and check valve kit so I found a used VST for $350 and put that sucker on it. Upon doing so found the HP fuel line to the rail cracked and leaking at the fitting. The last and toughest to find was a cut air line from the pump to the rail. The rubber was cut but the woven fibers were not. It was only after I took the compressor, tracker valve and regulators apart and was standing next to it with a remote starter did I feel the air blowing out. Tried using regular air house and some hose clamps to make due but they blew off (I think it had something to do with how hot that air gets but not sure). At this point I spent the $90 for the Merc line and got the actual hose clamps they recommend.

I don't know if this will help anyone in the future because this thing was kinda jacked up but I did want to say thanks to guys like Don for the insight that keeps shade tree guys like myself on the right track.

[EuropeanAM]

Thanks for the follow-up!