'06 Merc Optimax 150, need help w/ procedure to trouble-shoot overheat

[leaky]

Hi,

I've got a pair of these w/ 800 hours and what I've learned during the last 10 years is basically do the water pumps every year, the first time you have a problem do the pump, t-stats, poppet, and check/clean the screen on the port side of the block, and that resolves most issues. Once it didn't and I found a hose that had taken a set with somewhat of a restriction, and replacing that fixed the problem...

This time the typical replacement part routine did not help and I don't see any hose routing/kinking issues.

They are saltwater engines, however never stored in the salt and always flushed, it's possible but they really should not be jammed up with salt or corrosion deposits, they show like a freshwater bass boat engine because they always live on a trailer and get rinsed.

Here's the background: Winterizing my starboard engine, which ran fine all last season, it threw an overheat alarm, registering about 200 degrees on the smartcraft gauge. Before that I had started and stopped it a few times because it was not pumping water out the telltale, but that is kinda typical (I tend to jump the gun and if I just wait another 2 seconds it starts pumping).. It did seem to be pumping a little weak, however it was also below freezing and again it's kinda typical in that sort of weather to have blockages around the telltale path, so at the time figured I'd go through the procedures but most likely it just had been 1 year on an impeller and maybe some ice was slowing the water flow.

I installed a mercury water pump kit, poppet valve, t-stats, and checked the screen (which was perfectly clean)..

Today I took it out, ran fine for 1/2 mile of no wake zone, then at 3800 RPM for a mile, then at 5000 RPM for a bit, never getting above 150 degrees and was < 100 degrees when on a plane - then I slowed down to about 2000 RPM and was surprised by the guardian system going off - overheat, but the instant I pulled back the throttle (to more of an idle) it stopped and did not return when I throttled back up - indeed the starboard engine was about 50 degrees warmer, at about 170 versus the other at 120.

I didn't see any real difference in water flow watching the telltale - one of the guys on board said he noticed the starboard was pumping less, but I"m not sure if he realized when I was actually in gear above an idle - wish I checked water pressure but I didn't.. Further testing did seem to uncover temperature-wise I'm running hotter on the starboard, possibly leading to an intermittent overheat at some RPM.

Anyway - so I'm debating where to start. I think #1 I'll check the sensors. A bad sensor would have me running around in circles like this. Based on what I found when unplugging sensors, the temp I'm reading is a reading of two sensors located in the heads, maybe if one's bad you can see this..

#2 - triple check hoses, make sure no blockage in tell-tale, replace anything suspect

#3 - run engines, compare water flow/pressure in a controlled environment (not rocking around in the ocean), use temp gun to analyze situation, maybe determine if one area is heating up and that will lead me somewhere?

Then what? Start replacing parts I already just did? Water pump kit first? Poppet first? Test my new t-stats? Or is there something else more likely to point to a cause anyone can think of?

Thanks!

Jon

[half fast]

Check to see if the plastic insert where the poppet valve seats has moved out a little . It is a black plastic circular ring pressed into the block and it must be flush with the block .They will push out and when this happens the poppet has no travel and will cause the engine to over heat due to not being able to expel the water easily . If it moved just epoxy it in. hf...

[leaky]

Check to see if the plastic insert where the poppet valve seats has moved out a little . It is a black plastic circular ring pressed into the block and it must be flush with the block .They will push out and when this happens the poppet has no travel and will cause the engine to over heat due to not being able to expel the water easily . If it moved just epoxy it in. hf...

Thanks - I will check that next.

So here's what I found upon analyzing the engines, at least on the flush.

After 3 minutes of idling both heat up to around 140'ish wherever the smartcraft gauge measures. I suspect they keep heating up to some extent at dead idle but was just trying to figure out a baseline. The starboard engine though has higher water pressure - 2.0 instead versus the port at 1.5 psi.. Holding a steady 1500 RPM in neutral, again the starboard is at 9.5 psi and the port 7. Maybe that's just the new poppet & t-stats, or maybe that's a restriction showing, not sure.

Shooting the heads with a temp gun only shows all 4 are consistent, with both engines starboard head (the higher side) 5 degrees or so warmer.. Checking resistance across the temp sensor leads same on all, seems to be about 7k ohms at todays temp then goes to around 2.8k at 135 degrees by my temp gun. No particular area heats up.

Water flow wise the starboard (overheating) engine seems to be doing just fine as well, nothing I uncover there.

Pulled the t-stats and checked them against an old set and all 4 opened right about the same time - by my (cooking) gauge it was at 150 degrees.

I did find that I had the t-stat gaskets in backwards, which may cause some slight restriction, I wish that was it, but more likely is a negligible difference.

One hose I see I might be able to gain a little flow by replacing it, not kinked but maybe a little deformed, again more likely negligible but will replace.

Removed poppet - looks fine but will check that seat.

Picked up a water pump kit, although everything seems just fine for lack of a better idea will likely replace it and check the tube for potential restrictions.

Very little uncovered, not sure where to go next.

Jon

[leaky]

Well no idea what I fixed but I fixed it. As usual is a mystery, fixed a few tiny things out of order, replaced already newly replaced parts, engine runs colder than the other now..

Flipped the thermostat gaskets around, which are not exactly much different one way or the other but there is a little 1/16 inch lip I had backwards..

Replaced a couple hoses that were fine but maybe had a little dimple in them from being in cramped routing over time.

Removed my (new) poppet valve, checked it, looked great, replaced the seat and poppet anyway.

Found an opening in the wire for one temp sensor, taped over it, was not grounding out from any way I could tell, but I guess was possible.

Removed my (new) water pump, one thing that was odd here is the rubber seal that mates the tube going up to the powerhead w/ the pump body came off stuck to the tube and not in the water pump body.. *maybe* somehow was not well adhered to the pump body and was leaking somehow, kinda doubt it, but was odd as they do not usually come apart that way. Replaced assembly, this time I used permatex 2B on the gaskets because someone at some point was saying a little leak in those gaskets can allow air into the system and cause overheats, figured won't hurt until I got to replace it again later.

Gouped the hell out of the separator between exhaust & water pump w/ ultra black, trying to prevent any chance of exhaust gas into the pump.

Plenty of water pressure and runs nice and cold now - wish I knew what I fixed that did it, oh well!

Jon

[mn808gade]

only way is change ONLY one thing at a time.but hard to do,guessing it was grommet .was it on the END of the tube??-th

[XstreamVking]

One crazy thing about the opti's, the temp reading on the smartcraft is the compressor temp. Overheat uses the head sensors and/or the compressor temps to activate.....I installed a separate sensor and gauge to monitor head temps..

[leaky]

only way is change ONLY one thing at a time.but hard to do,guessing it was grommet .was it on the END of the tube??-th

Yes it came off stuck to the end of the tube and not in the pump body. I guess it could happen but never have seen it work that way before, which makes me think there was something different.

Now I didn't see any change in water pressure upon making these changes but temperature wise it was a notable difference.

[leaky]

One crazy thing about the opti's, the temp reading on the smartcraft is the compressor temp. Overheat uses the head sensors and/or the compressor temps to activate.....I installed a separate sensor and gauge to monitor head temps..

Hmmm.. From unplugging the sensors to me it seemed the temperature is some reading using both of the heads, ie when either are unplugged I get no temp reading (and an error), but I only get an error if I unplug the air compressor one, which actually has 4 wires (one that is grounded and one I don't know) versus the 2 wires on the head sensors. I didn't go as far as to figure out what each wire does but I assume the temp sensor on the air compressor provides a direct signal for an alarm.

At the time when I got my smartcraft gauges, I got the higher end gauges but did not spring for the square navigation-style readout, maybe those are better, but I think I was told my gauges did everything the screen did just not some navigational tools I didn't care to have mixed into my engines..

Whatever the case the whole setup is kinda hokey but would be much better with a couple tweaks to the design, I hope they realized this and improved it over time. The temperature area is ridiculous - 3 sensors and one readout, then even when it alarms (can read 90 degrees temp and alarm at the same time) it doesn't tell you which. Same for most of the other errors, ie ignition fault, injector fault, the computer knows, the gauge could tell you, but they designed it out. Granted armed with that little info I've found things like a spark plug boot not fully seated and a bad air injector, but it'd be a lot better (for the $$ they charge) if it just told you which, ie air injector #3 fault.

The GPH readout is great, having the engines trying to calculate how much fuel they have left in the tank, the screen flashing over to trim level after you make a little adjustment, etc.. etc.. is all just useless for me.

I've also got the digital speedo, which I would skip if I ever did this again because I've got no use for the speedo so the only thing you get out of it is another small screen that gives you similar info as the tachs, it does have an engine sync gauge but not very helpful versus just listening.

Oh and the wiring, most people never notice this but with the smartcraft hub, harnesses, and speedo and twin engines, it actually parallels the engines electrical system through the smartcraft wiring. They have you remove a fuse on one engine to attempt to prevent damage, but basically if you were to only connect one engine to a battery and attempt to trim the other engine, it backfeeds power through the smartcraft system to feed the trim pump on the engine that has no battery connected (and will actuate the pump but very slowly, eventually popping a fuse). Then when cranking an engine and the voltage drops a bit, for instance, you are always drawing a little through that same path. There is some simple problem present in their hub/gauge logic, it just isn't very well thought through.

If I ever did it again I'd probably do the setup myself then just let the dealer prep them before starting, but whatever the case would have them configured as 2 standalone engines, unaware of eachother with no shared wiring/hubs/harnesses.

Jon

[XstreamVking]

It all goes thru the computer. I have the system tach, and only use it to read the gph, volts, h2o psi and oil tank level. Shut everything else off with the menu. Still have the old analog gauge stuff installed too. My compressor runs 125, the cylinder head temp(using old style sender on star head) reads about 140...

[leaky]

It all goes thru the computer. I have the system tach, and only use it to read the gph, volts, h2o psi and oil tank level. Shut everything else off with the menu. Still have the old analog gauge stuff installed too. My compressor runs 125, the cylinder head temp(using old style sender on star head) reads about 140...

You must run at a fairly high RPM most of the time, I only see those sorts of temps (gun or by gauge) when < 1500 RPM, or by the gauge if I'm running > 4500. I cruise at 3200-4000 RPM (depending on if I'm in a rush and sea state) and at that point the engines are cold cold cold, last trip out was reading 87 degrees F in that RPM ballpark.

I gotta look at the manual again and figure out how to shut off all the other stuff. The first thing I have to do every time I turn the keys is hit mode to clear the error w/ fuel level (disconnected) and trim (disconnected trim sensors).

At the time when I had the engines installed I had 4 temp gauges, 2 water pressure, and 2 engine volt gauges on the dash, as well as tach and fuel level.

The shop that did the install told me "you can't run analog gauges with these engines", I just kinda took their word for it and that was a mistake. In reality they didn't want to think about how to do it and only wanted to plug in Mercury harnesses/gauges and/or were stupid. Shortly after I learned even an analog tach can be used.

Currently building a new boat that's getting a Merc MPI big block, definitely going to spend some time thinking through the gauge strategy - will have smartcraft to get the GPH and warnings, but will likely do what you did and add my own temp sensors if it's the same case w/ the inboard.

Jon

[XstreamVking]

Such a thing as too cold. Most smart craft readings are in the 120-135 range. THe 140 on mine is a head temp not a water temp. Compressor is water temp.

[leaky]

Such a thing as too cold. Most smart craft readings are in the 120-135 range. THe 140 on mine is a head temp not a water temp. Compressor is water temp.

What water temp you usually boating in? That and RPM is probably the biggest factor I see that changes temp - we are 50-55 F right now.
At low RPM going through the no wake I see more like 150, but once I throttle up, goes way down.

Basically w/ Opti's (my understanding) under power > 2000 RPM the poppet valve opens based on pressure, once that's open you could stick a plug in the t-stats and it wouldn't make a difference, water just blasts through the heads at sea temp.

Jon

[XstreamVking]

In fl we have 80's for water temp. I have 3 opti's and the temps stay fairly consistent whether on plane or at idle on the smart craft Gauges.