New-to-me 225 Optimax issues at higher RPM's

[thilltony]

OT470594P
2002
225 L OP
5750 Max RPM
21P Quicksilver Aluminum prop

I purchased this boat in unknown condition for a very good price. The seller said, "It runs okay, not perfect. Needs service, probably."

I pumped the fuel tank, changed the bulb and hose and added fresh fuel with additives. She started right up, and sounded pretty good. Ran her on lake Anna, and she ran well at low and medium speeds, but at the high end she would stumble a bit. I figured I just needed to run out the cobwebs

UNFORTUNATELY, none of the gauges on this boat work, but I ran her gently for a few trips, keeping RPM's down, and running fast for awhile every trip, and she ran well. The high-speed hiccup seemed to be getting better. 7 miles from the dock, it was getting dark, and a nasty thunderstorm was bearing down. I picked up and ran, but got a steady warning alarm. I cycled the key off and back on, and alarm stopped. Back on plane gently, and alarm sounds again. The storm hit, and it was ugly. I ran as gently as I could the remaining distance, alarm screaming the whole way, and made it back safely.

The compression test showed 110 PSI on all cyls, nice and even. Was relieved. Time to do some checking and servicing. Oil tank was full to brimming, remote tank full. Fuel was fresh. The plugs were all sooted up, so I got a fresh set. (NGK IZFR5G) I noticed green corrosion on the mounting bolts for the coils, so I carefully removed each one, cleaned everything and re-installed.

On the lake again, and she ran perfectly at medium speeds as usual. But when I picked it up for a WOT run, the alarm sounded 10 seconds into it, and the motor dropped RPM. (Guardian mode?) Ran fine afterwards and medium speeds. Definitely needs servicing or repair.

Unfortunately, the local Mercury dealer closed shop last fall, and the closest place is over 100 miles away, and they say they are very booked. I wish I could ship this thing to SC!

I've been reading on this forum, and it looks like there is a LOT of maintenance to do on these motors. I'm thinking that it might be a fuel restriction, so I'm planning to pull the VST tank and see if it's got crud in it. After that, I'm not sure what to do first.

Any suggestions?

I'm trying to decide if buying smart gauges would be a good first-course, should I find a shop, or should I just sell this thing?
I hate to say, I don't have a lot of money to put into this, and shops have let me down badly in the past.

[apdriver]

The experts will be along tomorrow probably. Since it is a new to you rig and probably not sure what maintenance has been done or not, probably a good idea to do an annual maintenance on it. Here’s a link for those items.

http://www.bbcboards.net/showthread.php?t=21874

water pump, lower unit service, filters, check thermostats. High end stumble can be several things but since you have no history need to do the basics first. JMO. You’re off to a good start.

[SilverFox579]

If Guardian is activating and you have a steady tone (not a beep) you are experiencing an alarm condition that needs to be addressed. Could be many things, if the water pump hasn't been serviced since you purchased this boat, it's the least expensive "guess". Do you have a telltale within 20secs or so of starting engine? Did you get a factory service manual after your post last year?

[Z518 Comanche]

I believe when you cycle the ignition key off and back on, it will override the alarm. When you said your oil tank in the boat was full. The tank in the bilge should only be 80% full.

[SilverFox579]

Depends which oil tank he's referring to (and he didn't say) the engine reservoir must be 100% full at all times, no air present, the remote tank (in boat) should be no less than 30% and no more than 80% full.

[thilltony]

Thank you for the very informative replies! Yes, the steady alarm was scary.

• I did not know the 80% rule. Thank you for that info. What happens if overfilled? I probably filled it 95% initially.

• The engine oil tank was brimming to the top, no air at all.
• Yes, I got the factory service manual. Have been reading, trying to get a grip on the basics. I've mostly had OMC, so lots to learn!
• I did the lower unit work first thing. Quick, strong water flow. I'm pretty sure it wasn't overheating, but I'll look up poppet valve service.

Finding all the filters in the motor is my top priority at this point. Anything that could reduce fuel flow.

Thank you so much for the suggestions. I will start reading the articles and posts.

[SilverFox579]

The remote tank needs air space so crankcase pressure can pressurize it and push oil to engine reservoir.

Reason I asked about tell tale is that it is the compressor cooling circuit outlet, if telltale is delayed or weak, a compressor overheat is possible. Unlike many engines, on an Optimax, the telltale does not come from engine cooling circuit and cannot be used as indicator of cooling system health.

Without engine data it's difficult to suggest a course of action. At this point I'd find a marine service facility with the ability to plug into your engine computer, read and download codes.

[Z518 Comanche]

You really need to take it to a dealer and have them check it.

[06 SB]

SO MANY things this could be and the only way to know for sure is to get it to a dealer. Independent shops should have the tools to at least read the alarm codes so try one of them.

Is there any chance you are on the limiter?
What boat, because a 21P aluminum prop is awfully small for a bass boat.
Have you cleaned the compressor strainer?
Don’t cycle the key off/on. It NEVER solves issues. It just masks them while the motor is potentially eating itself.
If the motor is Smartcraft compatible then I HIGHLY recommend a Smartcraft device.

[EuropeanAM]

SO MANY things this could be and the only way to know for sure is to get it to a dealer. Independent shops should have the tools to at least read the alarm codes so try one of them.

Is there any chance you are on the limiter?
What boat, because a 21P aluminum prop is awfully small for a bass boat.
Have you cleaned the compressor strainer?
Don’t cycle the key off/on. It NEVER solves issues. It just masks them while the motor is potentially eating itself.
If the motor is Smartcraft compatible then I HIGHLY recommend a Smartcraft device.

^^^ ALL good advice. Be sure to check out the Dealer Locator on Mercury's Website... surely there's at least one dealer closer than 100 miles from you?

https://www.mercurymarine.com/en/us/find-a-dealer/

Definitely see if you can get PRINTOUTS of the Run History and Freeze Frame (Fault) History. Without that, you're unlikely to "guess" which one of dozens of potential Faults is actually the cause of the CRITICAL warning horn.

One last thing: I would strongly recommend you not run the engine again until this problem has been diagnosed/addressed.

[thilltony]

Thank you for the warnings and good advice. I found two dealers 35 and 50 miles away. Will call tomorrow and see who can check it soonest.

It's possible I hit the rev limiter the last time out. After cleaning up the ignition system, it seemed to have more power and jumped on plane effortlessly. It had a 19p when I got it, and I swapped for a 21p, but that isn't much better, is it? I have a 24p Quicksilver SS prop I'm going to try after getting it scanned and fixed.

Vessel View Mobile is coming, as are new Faria gauges. I feel dumber and dumber, when I think about it. What was I doing running without a good tach?

This shows that it's time for me to slow down. I have too many irons in the fire. I've decided to quit my hobby of buying boats, cleaning them up and then trading up. I started with a $400 boat, and have worked my way up to some pretty nice ones. The big Cajun is now gone, as is the green Javelin. I'm down to two nice 20' boats, and it's really deciding between the Optimax or the Venom. The Optimax is impressive, but I worry about the mechanical complexity. The Venom should be easier to maintain, but it's older, louder and less efficient.

[EuropeanAM]

With the Optimax... if you simply think of the fuel and ignition systems in a "compartmental" fashion, it helps.

Remove those two systems and the electronics, and you're basically left with a simple, 2-stroke powerhead. Slightly different heads and dished pistons, but otherwise... a big, over-grown 6 cylinder chain-saw engine.

[thilltony]

This is true. I really like the fact that I will soon have digital readouts on this Mercury. I have new decals for it, and once those get done, it will look like a new engine.

It's the compressor that scares me the most. I've heard they tend to blow up with little warning, and they destroy the engine when they do. Is this true? Is there any preventative maintenance, or early warning system to catch it before it goes?

[EuropeanAM]

Not really destroy the engine, that's a pretty rare scenario. Yes, they may spread debris through the fuel rails and/or direct injectors if the compressor fails.

There's way too much "hype" about compressors out there on the interweb written by Tube-Certified Internet Engineers (mostly). The lions-share of them run for many years (sometimes well into the thousands of hours). We just "hear" about the ones that failed, when folks come on the forums looking for help.

Take a good look through the topics in the FAQ Section. Many of them pertain to this engine, and provide you with suggestions to use to help save money.

[thilltony]

Not really destroy the engine, that's a pretty rare scenario. Yes, they may spread debris through the fuel rails and/or direct injectors if the compressor fails.

There's way too much "hype" about compressors out there on the interweb written by Tube-Certified Internet Engineers (mostly). The lions-share of them run for many years (sometimes well into the thousands of hours). We just "hear" about the ones that failed, when folks come on the forums looking for help.

Take a good look through the topics in the FAQ Section. Many of them pertain to this engine, and provide you with suggestions to use to help save money.

Thank you for that. That is reassuring, coming from you. I will keep reading up on them.

I'm not afraid to take a chance. I've run Ficht engines for many years now, with almost no issues once I get them running right. I bought them cheap, worked out the bugs, and they have been almost dead-reliable for years. I had my first real issue a few weeks ago, which turned out to just be a clogged VST vent hose. Learned a lot, thanks to the guys here. I almost wish I hadn't sold that boat, but it went to a workmate, so I can see it anytime I want.

I'm hoping this engine will be similar, as I like many things about it. As crazy as it sounds, I wish it was a 175 HP. 225 is max for the boat, and the back sure squats low. The 175 is a good bit lighter, and seems perfect to me, but maybe that will change, once I feel WOT, if it's not too scary.

[Jefff]

Poppet valve not opening up at higher rpm I have read may cause sputtering issue from what I’ve read in manual, Just a FYI

[EuropeanAM]

Poppet valve not opening up at higher rpm I have read may cause sputtering issue from what I’ve read in manual, Just a FYI

That would be a pretty rare situation... won't go so far as to say "never", but will say that I've not yet seen it happen.

You would also tend to have WAY crazy high water pressure ...