Overheat alarm HPDI

[CaptainJim]

we trolled on friday pulling stretch 30s and the motor basically idling all day in and out of gear.

towards the end of the trip my overheat alarm went off on my HPDI, so we shut it down and tried to diagnose the problem... the heads didnt seem hot, and the telltale was still pissing, starting to think my sensor or thermostat is bad.

we let the motor cool off, and we raised the motor and unscrewed the screen to see if it was blocked, it wasnt. We then started it, the alarm was gone, then we ran the motor at cruise and the telltale was still peeing like a firehose...

not sure if my waterpump isnt putting out enough at idle, or if my thermostat or sensor is shot, or if I sucked some snot into the motor while trolling (we were running through weedlines most of the morning, however the intake wasnt blocked when the alarm went off)


anyone have any ideas? My telltake pees at idle, and really has GREAT pressure at 4000rpm cruise...the alarm never came back...Could idling all day cause this?

 

[ReelyNauti]

Last year my buddies did the same thing , im not sure it will help but it turned out to be a corroded wire on the thermo... when it got hot the corrosion on the connection/wire set the alarm off !!!... new connector and wire and a new sensor did the trick
good luck

 

[CaptainJim]

im starting to lean towards i picked up some snot in the motor... i'm going to keep an eye on it.

so far i've narrowed it down to:

1) weak water pump (second most likely, water pump has only 1 full season on it, so i hope it isnt this)

2) stuck poppet valve (least likely)

3) malfunctioning overheat sensor (likely)

4) snot/debris in the water (most likely)



i took a picture of my motor at idle neutral in the slip tonight...i dont think the water pump is weak at idle, since the telltale seems to be pushing at an acceptable pressure.

 

[CaptainJim]

still working on this issue.

replaced the thermostats last week (they were like rocks, even despite my religious flushing)

engine overheat alarms at idle in the slip after 5 minutes, even with the new thermos, and i can feel them opening and closing.

i'm hauling out tomorrow mornign and doing the water pump myself... i have a mechanic whos going to show me the ropes in exchange for a fishing trip.

i was on a buddies boat with twin 150 HPDIs and his water pumps at idle are pushing at least 2x the pressure through the telltale, i beleive my water pump is shot after one season.

 

[CaptainJim]

Pulled the lower unit with a buddy with ob mechanical experience, the impeller was in good shape, however the wear plate was a little grooved. Thank goodness I bought the rebuild kit and the two locking collars, replaced everything including the collars which were destroyed during dissassembly.

The new water pump kit peed a LOT harder. It seems my mechanic didn't install the whole kit last winter like I asked, only the impeller. The grooved wear plate caused low water pressure at idle.

The water pump process was so easy that I won't be paying someone else to do it for me ever again....one parker dealer quoted me 2.5 hrs labor at 125$ an hour. For something two morons did in a parking lot in 45 minutes.

 

[CaptainJim]

Genuine Yamaha. Was in 90% condition.

 

[Megabyte]

My experience may not apply as my motor is an OX66, not an HPDI.

First trip out fishing after buying the boat in 2003 and I was trolling down-Bay with the current at idle. After about 20 minutes, my overheat alarm went off.

Killed the motor and raised it to make sure I hadn't picked up a plastic bag... nothing there.
Since the boat had just been to the dealer to have the motor serviced, I called the service manager.

Service manager asked how many RPM's I was turning when the overheat alarmed (600rpm). He told me that big-block Yamahas don't pump enough water at that rpm to keep themselves cool for 20 minutes, and that they generally set the idle at 700, with the tach just flashing at 800. He told me to raise my engine rpm's to 800 and let him know if I had any more issues.

We trolled another 6 hours that day and the alarm never went off.

The next year when I had the motor serviced, the alarm went off on the technician when they had the boat sitting in the 'service pool'.
They discovered that (apparently) the previous owner had never flushed the motor, and she had a LOT of salt build-up in her.
The dealer actually removed the heads and dug most of the salt out. The rest was dealt with using a heavy Salt-Away treatment.

As you discovered, it is not uncommon for a motor technician to only replace the impeller, if that is what you tell him. I was told that when making the request to always say "replace the water pump" so you get the whole kit.
Poppits and t-stats should be replaced at the same time as the water pump.

Ever since those early 'teething years', I've never again had an overheat issue. Water pump, poppits, and t-stats are replaced every 2 to 3 years (depending on hours of use) and the motor gets flushed with fresh water for about 20 minutes after every trip.

In addition, I'll give the motor a salt-away treatment as PM once or twice a season. It's just good insurance.
The motor runs stronger now than when I bought her (fuel treated with Ringfree, StarTron, and StaBil at every fill-up), and no overheats in the past 5 years with the above maintenance cycle.

Hope this helps.

 

[CaptainJim]

i'm going to do a de-salt on the system...is there a method and product you recommend kevin?

when i pulled the t-stats out the inside of the heads looked GOOD but had a little salt crust on them... not bad but a LITTLE....

motor ran great yesterday, lots of idling and no alarms.

funny the wear plate only had a TINY groove in it, i guess that was enough to reduce my low rpm water pressure

 

[CaptainJim]

Service manager asked how many RPM's I was turning when the overheat alarmed (600rpm). He told me that big-block Yamahas don't pump enough water at that rpm to keep themselves cool for 20 minutes, and that they generally set the idle at 700, with the tach just flashing at 800. He told me to raise my engine rpm's to 800 and let him know if I had any more issues.

my motor idles at 700 flashing 800 in neutral, but in gear idle is 600 flat...hrm. either way it overheated just sitting at idle before the new water pump,.

 

[Megabyte]

i'm going to do a de-salt on the system...is there a method and product you recommend kevin?

I used the Salt Away kit and just followed the directions you see below.
Once you introduce the Salt Away product into the motor, I would let it sit overnight.
Since this is the first time for your motor, I'd keep the kit on board and give it two or three applications over a period of time. After that, fresh water flushes should be fine.
I only use the Salt Away product a couple of times a season now, just to be on the safe side. The rest of the time, I just do a freshwater flush.

http://www.saltawayproducts.com/EngineFlushPage.htm

Instructions – Using Flush Port Fitting

1. Remove 4-ounce cup of Mixing Unit and fill with Salt-Away. Be careful not to lose O-ring.

2. Replace cup. Always make sure the O-ring is seated on the groove on top of the cup before replacing.

3. Connect garden hose to back of Salt-Away Mixing Unit. Mixing Unit is in 'off' position.

4. Connect front end of Mixing Unit to a quick-connect device, or a short piece of hose. Attach the quick-connect device or hose to the port connection. (Some port openings are recessed too deeply to accept the Mixing Unit directly.)

5. Turn on water. Mixing Unit has been tested to withstand water pressure up to 60 psi. Higher pressure may cause the unit to malfunction.

6. Turn Salt-Away Mixing Unit to 'Salt-Away' (ON) position. This position mixes Salt-Away and water to the correct ratio for removing salt. Water pressure from the hose easily flushes this mixture through the engine.

7. Watch for the Salt-Away foaming action to exit the exhaust.

8. Turn Mixing Unit valve to the 'off' position after Salt-Away foaming action has appeared, about 20-30 seconds, while Salt-Away is still present throughout the cooling system. It is ok to flush for up to 1 minute. Flushing for more than 1 minute is unnecessary, and the product is being wasted.

9. Remove equipment from the flushing port and close port.

10. Do not rinse Salt-Away out of engine with fresh water. Leave inside so that its corrosion inhibitors can protect the metal from rusting and corroding, and so that the salt removing agent can begin to break down salt build-up. See instructions for removing salt build-up.