4.3L TKS intermittent engine alarm

[natemeins]

Hey everyone. Need some help troubleshooting an intermittent but worsening issue. This is going to bed long-winded, but bear with me. Here's some back story:

I have a 2007 4.3L TKS engine w/ Alpha One Gen II outdrive on a 2007 Bryant 210. I've owned it since 2016, I'm the 3rd owner, when I purchased it it only has 26.5 hours. Prior to this season it had 291.3hrs, it now has 312.0hrs. It has NEVER seen salt water, only lakes in SW Missouri and Beaver Lake in NW Arkansas. Being an aircraft mechanic myself I'm quite diligent on maintaining it regularly. I should also note that this engine has the engine alarm "block point change" of having a two-wire water temp sensor (black and yellow wires) on the port side of the thermostat housing, the wires leading back to the ignition control module, to act as the water over temp switch for the engine alarm system. Naturally I have no data for this change, all my service manuals don't reference it or explain it. I have looked and looked for data for this change from Mercury to no avail. I have had to go old-school and do ringouts and chasing wires to see how the engine alarm system is connected.

For the last 2 seasons it has had an intermittent engine alarm. It would beep very quickly two maybe 3 times during a day, usually about the time the engine is fully heat soaked- never at idle, never at the start of the day, never immediately after engine start. Most times this would occur while wakeboarding, other times while on an easy but steady cruise. I'm almost never at WOT, while wakeboarding we do 18-21 mph with an engine RPM around 3000-3200rpm and the boat heavy. Cruise is usually around 24-27mph with RPM around 3200-3700RPM, no ballast, just myself, my wife, and two young daughters. These numbers may not add up as I've since replaced the prop from a 5-blade Hi-Five 19 pitch to a 17 pitch for better hole shot while doing tow sports. The WOT numbers are very close to 4800RPM but not over, max speed has been reduced to around 37-40mph GPS (again, top speed is not an issue for me, I want the low end power, but I did verify I am still within proper operating WOT range). The last season the beeping was happening more often. Never steady, almost like a short was in the wiring and it sounded like a telegraph. At least two years ago I replaced the water temp gauge sensor along with the thermostat as a "just in case". Last year the event was happening a bit more often, again with no specific reason. The temp gauge was a steady 175°-180°F when fully heat soaked in the middle of the summer. I replaced the thermostat again yet the temp remained. I did try pulling the contacts for the gear lube monitor and engine oil low press switch to try to isolate the alarm. As intermittent as it was I couldn't nail it down. It also seemed the engine was low on power compared to previous seasons.

This last winter I pulled the entire sterndrive assembly out to check engine alignment, as I found the engine mounts loose. All looked well. While I was there I verified all bellows were still in good shape with no tears or leaks. Gimbal bearing was in good shape. Although a royal PITA I got it back on with no apparent issue. With this I also replaced the gear oil, raw water pump, and lower gearbox upper bearing seal, engine oil/filter change, fuel filter and fuel filter screen on carb, replaced the spark plugs and verified proper gap of 0.045", replaced the spark plug wires, ignition coil (went with an MSD coil), oil low pressure switch, gear lube monitor reservoir, water temp gauge, and the two-wire water temp sensor. I also wound up replacing the engine water circulating pump after a friend of mine was having issues with his boat overheating. Turns out my pump's bearings were beginning to seize. With this find I was certain I had found the culprit.

The first outing happened with no issues. Water temp indicated 160°F when fully warmed up. Really thought I had nailed it. The next outing the alarm began to happen again but this time the alarm was happening way more often and the beeping was becoming more steady. The temp gauge was locked-in at 160°F. I isolated the alarm to the two-wire water temp sensor. With it pulled it never came back, however after long cruises or wakeboarding, after pulling back to idle, a noticeable light steam was coming from the sterndrive I have never noticed before. I assumed it was likely due to the engine exhaust being much hotter because the ignition control module could advance to max with no water temp issues ( I had it unplugged). I plugged it back in and again the alarms were happening all the time while running, not at idle, never steady for more than a second or two, again the gauge nailed at 160°. I replaced the temp sensor figuring I found the problem. This was last weekend. No alarms while wakeboarding until a turn, then it would beep two or three times, then when straightening out it would go quiet. I played around with engine trim and found with higher trim settings it would get worse. At a cruise of around 27MPH it was happening the most, sometimes steady for several seconds. I went to WOT thinking maybe something was clogged up or just needed "cleaning" out and it sorta got better, especially when I throttled back down to 3700RPM. When I pulled back to idle for a few seconds then went slightly off-idle it beeped quickly. We called it a day.

One other thing to note is that with the boat sitting in the water still, engine not running, I checked the gear oil level. The oil was frothy. I've NEVER seen this in the past. It was also leaking from the bottle cap and has made a mess of the bilge. If I had to guess the amount it would be less than 2 or 3 oz.

Today I pulled the lower unit out. My thinking has been perhaps there's an exhaust leak pressurizing the gear oil causing it to froth up, and injecting hot air bubbles in the cooling system that the temp gauge will not react fast enough to but perhaps the water temp sensor/ignition control module will and cause the alarm. Draining the oil no water was noted, only dark blue clean oil. However pulling the vent cap I noted a slight hiss, indicating either a vacuum or a slight pressure in the gear oil system. Odd. Apart from that I found no obvious defects. The water inlet pipe appeared to be seated properly and the oil passage o-ring was where it should be.

So I'm at a loss. Is it possible that the Ignition Control Module (ICM) doesn't like the MSD brand coil? I did verify that it is the proper coil for this type ignition system. DO I have a failing ICM? Lord, I hope not as those buggers are stupid expensive. Has anyone else seen anything like this? I did go through the engine wiring and verify no shorts or breaks in the engine alarm circuit. All ringouts were good. Is it possible something in the exhaust is blocked causing the water to back up? If that's the case why haven't I seen an increase in water temp at the gauge, given I have a new gauge and two-year-old sender installed? Really, that's the kicker: I know the alarm is due to a "water temp high" condition but both the new and old gauges show 160°F, even after a new thermostat, water circulating pump, and new water temp sensor.

Any guidance you all could give me into what to look for or something I've done wrong would be a HUGE help. Thanks for hanging-in this long and whatever advice you can pass along.

- Nate

 

[alldodge]

went with an MSD coil

MSD usually means great fuel economy because your getting towed in. Nothing wrong with the old coil

checked the gear oil level. The oil was frothy

Nothing wrong here other then the bottle cap valve is no longer working. Its a one way valve and allows pressure in but not out. With oil coming out means the cap valve has gone bad

A lot of words and may have missed it, but did you replace the temp switch? (one with Yellow/Black wire)

How about a serial number?

 

[natemeins]

Engine S/N: 0W688892
Sterndrive S/N: 0W894217

As far as the ignition components replaced, I was chasing why power seemed to be down. It wasn't until later I figured it was due to the ICM retarding the timing due to high temps. I figured after 10 years these things were starting to show their age and they're easy replacements. I still have the original coil and plan to put it back in before this weekend.

As far as the two-wire temp sensor, yes I've replaced it. Looking back at my old parts I kept it appears I've replaced it now three times. I now have another gauge sensor (single wire) ordered and will replace it.

So after writing the original post I ordered another pump rebuild kit, bellhousing gasket kit, and water temp gauge temp sensor, just in case. Went ahead and pulled the pump assembly and found that two vanes were pointed in the wrong direction. The others were correct per the book. Thinking they may have shifted when I pulled the housing off I pulled the impeller out to see how the vanes had taken their set. Sure enough they had been pointing the wrong way. I'm pretty anal when it comes to these things, especially when you can't verify an installation once it's installed, so that surprised me. However where I think I may have gone wrong was I reassembled the pump and installed the lower unit to the bellhousing prior to installing the entire sterndrive back onto the transom. Given the issues I had getting everything aligned, especially the drive shaft, it's entirely likely I turned the driveshaft CCW to align the splines to the engine coupler, and thereby turning a lubricated but dry impeller the wrong way and inadvertently shifting the vanes. I probably should've installed the bellhousing first before installing the lower unit. Anyway after about 30 minutes of the impeller sitting out the vanes straightened out (i.e. permanent "set" has not taken place yet) so I set the impeller properly (must've checked it half a dozen times), reinstalled the pump assembly, and reinstalled the lower unit. As my new parts will not arrive till next week I'll take it out this weekend and see how it runs.

I understand vane position is critical for proper pump operation, but would one or two vanes cause a significant enough water flow loss to cause the engine alarm to intermittently go off yet the water temp gauge to remain within spec, assuming the gauge and gauge sensor is good? With the older systems using a water temp high switch for the engine alarm, what temperature does the alarm go off?

 

[alldodge]

Thanks for the SN's
Being you have a Gen 2 drive, installing the impeller turned opposite should not have hurt or caused it not to pump correctly, unless an old impeller was used. achris has more then once that the impeller will just fix it self once the motor is started

Get a piece of clear hose and barbed fittings from the hardware store. Place the hose between the out drive and thermostat housing. Your looking for bubbles.

Also good to use clear hose going to exhaust

 

[natemeins]

Just to be clear...
Bypass the raw water hose from the transom to the inlet on the T-stat housing? I'm looking for bubbles from the raw water pump?

Maybe it doesn't matter but one thing I noticed while running on muffs yesterday was that very little if any water was exiting from the thru-hub. Maybe a fine mist at best after full warm up. Most if not all was coming from the two exhaust ports on the transom mount. It's been a while since I've run it on muffs but I seem to recall more water usually comes out of the thru-hub than what I saw.

 

[alldodge]

No, don't bypass, remove hose coming from the drive and going into the thermostat housing. Take the clear hose and attach to thermostat housing where the hose was just removed, then attach the drive hose to the other end of the clear hose.

The garden hose doesn't supply all the water the pump can move, so just seeing it in the relief ports is ok.

The test with a clear hose is to be done on the water and not on a garden hose

 

[natemeins]

Understood. Will give that a try. Thanks for the idea.

 

[Fun Times]

Next time the alarm sounds, simply try disconnecting both of the wire harnesses plugs that go into the ICM Module (Ignition Control Module) as chances are the problem lies hidden within the ICM Module as it has been recorded here on iboats a low number of times over the years that un-connecting the wire plugs has resolved an hard to find intermittent engine alarm like this especially around the 2006 year models.

It's item number 7, https://www.mercruiserparts.com/bam/subassembly/31493/12833/40

Let us know, good luck.

 

[natemeins]

Thanks for this, very interesting. Just to be clear, the thinking is that the issue resides as an intermittent internal failure of the ICM and the only fix is to replace it? That bugger ain’t cheap. Has there been an updated part that resolves the issue?

 

[Fun Times]

Thanks for this, very interesting. Just to be clear, the thinking is that the issue resides as an intermittent internal failure of the ICM and the only fix is to replace it? That bugger ain’t cheap. Has there been an updated part that resolves the issue?

The theory I mentioned is honestly more of an past iboats forum members working together over the years sort of under my theorized guidance of trying to solve Mercruiser carbureted engines mainly in and around the 2006 mark that have experienced what seemed unsolvable intermittent engine alarms like yours seems to be doing....I'm not saying unplugging the wiring harness will definitely stop your warning horn from sounding but seemingly with all other avenues nearing exhaustion, the theory to try unplugging the wiring harnesses for a minute, inspecting the wire pin terminals, maybe cleaning them if needed, ensuring the wire pins are pushed inwards and seated tightly then go for a boat ride is pretty easy and free to try.

To my knowledge no one has come back and mentioned they bought or needed to buy a new ICM to stop the warning horn overall...Only un-connecting the plugs seems to have worked thus far...Plus I'm not even sure if Mercuiser is/was aware of this possible issue or solved it silently as I don't recall seeing any published information regarding it.

Just recently there was a new topic posted that seemed to had gone sideways regarding this whole situation but I don't think you'll need to buy a new ICM.

The famous random overtemp alarm for no reason = https://forums.iboats.com/threads/the-famous-random-overtemp-alarm-for-no-reason.731494/

Does your boat have a battery switch by chance? Just to add to a continuing theory here but maybe powering the ICM down is needed internally every once in awhile to help exercise moving mechanical parts on the inside like relays have for example.

If you seemed to had a slight engine performance loss during the event, then it is known that the engine temp overheat part of the design was supposed to affect engine timing in these units...So maybe.

Oh and by the way, if this was a aircraft mechanic website, I would simply say try buying a new ICM:wof: because there ain't no stopping to go try something like this real quick.

Hope this helps somehow, good luck.

 

[natemeins]

This helps a lot, thanks. Will dig into the thread you linked. The fact I can get it to stop by simply unplugging the 2-wire temp sensor tells me it's related but I certainly want to make that a last resort option.

don't know if the defect I found with the raw water pump impeller will solve my issue (one can hope), but the way it acts it feels electronic, leading me to believe it's going to be the ICM. I seem to recall while I was doing wire ringouts and chasing I had both those connectors off and did a good inspection. Oftentimes on aircraft intermittent squawks are due to light corrosion buildup on connector contacts or a pin pushed slightly and can be resolved by just unplugging and reconnecting the connector. But it certainly doesn't hurt to look again more closely.

Yes, I do have a battery cutoff switch, doesn't hurt to try.

I'll get it out Sunday and will do some more troubleshooting. Will certainly let y'all know what I find.

Thanks again for the info and advice, everyone!

*edit* - Wow, I feel like a real buffoon starting a new thread when the link posted above links to other threads of the near identical issue I'm having. I too must work on my search skills.
Thanks again, Fun Times. Looking forward to this weekend and give the unplug/plug of the ICM a try!

 

[natemeins]

Was thinking about this last night, has anyone tried using dielectric grease on the engine connectors, specifically the ICM, as a corrosion/moisture inhibitor and increase continuity? I use it a lot on wiring and bulb connectors for trailers and motorcycles. Is there a risk of shorting the unit by doing this? Can't shake the idea that reseating the connectors and pins is doing nothing but just cleaning the contacts. The bilge is a moist environment and the ICM sitting right on top of the exhaust means it gets tons of hot moist air and then bakes, begging for the electronic smoke to be let out. Perhaps even adding a heat barrier between the ICM and exhaust might help?

 

[Fun Times]

Was thinking about this last night, has anyone tried using dielectric grease on the engine connectors, specifically the ICM, as a corrosion/moisture inhibitor and increase continuity? I use it a lot on wiring and bulb connectors for trailers and motorcycles. Is there a risk of shorting the unit by doing this? Can't shake the idea that reseating the connectors and pins is doing nothing but just cleaning the contacts. The bilge is a moist environment and the ICM sitting right on top of the exhaust means it gets tons of hot moist air and then bakes, begging for the electronic smoke to be let out. Perhaps even adding a heat barrier between the ICM and exhaust might help?

Now try not to go losing to much sleep just yet over this one as you still have to try option #1 to see if the theorized process helps your situation for either a shot or long time period or even at all.

Some exhaust risers run warm while others run cool...Check your temps a few times on your next trip out and judge from there.

 

[natemeins]

Well I committed the cardinal rule of troubleshooting and shotgunned a couple things before testing: in addition to finding the impeller vanes misaligned I pulled the ICM connectors, did some visual inspections, bent the wiring a bit at the connectors and pushed them in to “reseat” the pins for good measure and reconnected AND I put the original temp sensor back on. Doing some resistance checks with all the temp sensors I found that the original had a higher resistance value for a given temperature overall, usually around 100 ohms, compared to the other two. With these sensors resistance is inversely proportional to temperature so if it meant the alarm would need a bit more temp to lower the resistance value to sound The alarm then it was worth trying.

Sunday we did one short hop to our fav anchor spot and of course no alarm, didn’t expect it to. Later we loaded all the ballast up and cruised at around 24mph (3300-3400 rpm) to our fav channel for wakeboarding, (about 15-20 minutes) followed by about 2 hours worth of laps wakeboarding. We worked the engine pretty good.
No alarm.
Not a sound. Engine seemed happy and was making great power.

So what fixed it? Don’t know, thanks to shotgun troubleshooting. Although I still think in my case it was the impeller, it was probably just as Fun Times has been preaching and the ICM connector reseat did the trick. Can’t thank you enough! Now we’ll see if we hear from it the rest of the season.

 

[Fun Times]

natemeins , Good to hear the problem seems to have disappeared for you...Hope it remains and please update the thread should it come back (Or it don't) and maybe if at all possible keep track of the general engine hours, time used etc. as it would be interesting to really know further details as time goes by as like mentioned to my knowledge this is more of an iboats solution vs anything else like servicing dealers out there, etc..

Also I can only assume in theory that (especially since you have one) 'Physically using the battery switch on carbureted engines (especially around the 2006 year mark) when not in use can only help lower the chances of the warning horn from sounding off.:encouragement:

Thanks and good luck.:thumb: