SX150 TXRA Overheat Alarm (2002/ 2 Stroke)

[CTJackC!]

Late last year I picked up a 2120 Parker Sport Cabin, powered with a 150 Yamaha 2 stroke (TXRA), all 2002. The boat only had 400 hours on it and it ran great during the sea trial. During the first few months of use I would occasionally get an overheat alarm (no real pattern when it would come on), I would shut the engine down and wait a few minutes and then it would fire up (no alarm) and run fine. Some trips there would be one alarm, some trips up to 4 periods of alarm. The water pump has always been pumping, and the engine runs very smooth (even when in alarm mode). My boat is at a small marina and there is engine service and they told me to keep running the boat and see if the alarm clears up with use. Happily after 2 months all the alarms stopped and I had no issues. Unfortunately, the alarms returned over the past 2 trips. Weirdly, did not get any alarms during the warmest water period in Long Island Sound. (Note, I'm in CT and fishing/boating season is fast coming to a close so I won't be running the boat much longer this year.)

In my chats with the marina, the plan is to replace the water pump, thermostats, etc. in the spring before launch. I don't have the entire service record for the engine, my marina did replace the fuel pumps and did work on the fuel system prior to launch this year.

I was pondering repowering with a new Yamaha 200 In Line 4 but with only 470 hours on the engine and a fuel curve that is not that much different than the 150 2 stroke it does appear keeping the old 2 stroke running makes more sense. The boat and engine appears to be well maintained, just not run enough. (I put 60 hours on it this year, so that is being corrected.) The engine is flushed at the end of every trip for at least 15 minutes.

Just looking for some input on next steps. Not sure if a sensor ever goes bad. I don't like putting more money in an old 2 stroke but at the same time the engine matches this boat fairly well and runs great except for the alarm issue (which I thought was behind me). I've watched the videos on pulling the heads for clear out internal blockages but I didn't want to go that far.

My last trip - 5 miles to the fishing spot - 2 alarms going to the fishing spot, shut down for a minute each time, the boat ran fine and came out of alarm mode (3500-4000 RPMS). Trip back - 4200 RPMS, no alarm at all.

Thanks- Jack

[fairdeal]

the engine runs very smooth (even when in alarm mode).

I'm weak on my 2-stroke expertise -
but I thought an overheat alarm on that engine
would drop/limit rpm to NMT 2,000

(but yes, run smooth below that...)

does your tach have a high temp warning indicator /
are you certain its an overheat alarm?

[99yam40]

what RPMs were you running each time when the alarms came in this last time?
has it always been around the same RPM?
and did it limit the RPM like fairdeal said?

did you try just idling instead of shutting down?
is there anything in the water around there that could restrict the water intake from time to time?

I my self would pull the stats and inspect the passages to see if there is a need for cleaning passages.
if the alarm is sounding during low RPM, I would also look at the PRV to make sure it is not sticking open

[CTJackC!]

The 703 Remote Control Box Manual just states to throttle down, and proceed to your nearest port at low speed, the engine does not appear to have a limiter (SAFE mode). I have not really tried to sit in neutral to see if the alarm clears. The alarm is definitely from the "control box" and it appears the only alarm related to the control box is overheat.

The alarm typically occurs at mid- 3/4 throttle. I have had an alarm very early in the season when I was motoring around 2000 RPMS between fishing spots.

So, If I pull the stats what is the procedure to inspect the passages? I did see a discussion about a iPhone accessory (camera). I've watched more than a few You Tube videos about clogged up heads and the use of small picks, etc, removing the gunk. Salt Away seems to get mixed reviews.

Thanks- Jack

[fairdeal]

The alarm is definitely from the "control box" and it appears the only alarm related to the control box is overheat

the warning horn is inside the 703, yes.
But the engine can sound that horn for overheat,
or oil tank level,
or - apparently - "oil filter clogging".

[CTJackC!]

fairdeal - thanks for the education on the alarm system. When the mechanic worked on the boat in the spring (fuel system) he also drained the entire oil tank, replaced the filter, etc. I'm somewhat of a zealot and keep the tank full but with colder weather perhaps the oil got a more vicious and perhaps another filter is needed.

In terms of the overheat alarm - other than the alarm from the control box what is the typical alarm on the tach? I have not notices any red lights etc. The boat has the original gauges, etc.

I might try to run it on this Friday and then pull it for the year after that.

Thanks - Jack

[99yam40]

need to know what gauges you have,
but I would think there should be a light close to the oil or overheat symbol that should light up while the problem is active.

need to test the system to make sure it all works as it should
both low oil and overheat should limit RPM
the oil filter would limit oil flow to the oil tank on motor, so you could pull the cowling and look to see if that was low, but need to shut off the key immediately when the alarm sounds to check it , other wise when you slow down it could be still trying to fill.

as far as the stats inspection, if you see a bunch of junk in the hole once you pull the stats, you can bet there is junk everywhere else inside too.
that does not a clean area behind the stats also means the rest is clear, but just something to look at

[zenoahphobic]

Sounds very much siren is overheat warning.
Coming and going tends to confirm alarm at least working properly.
The alarm going at low speed could indicate overheating because the water pump is not able to supply enough water. That could be worn out pump, or some obstruction like blocked passages or thermostat(s) not opening as they should.
Now alarm going away after idle suggests water pump able to increase water flow in spite of obstruction, if there was any!
As the alarm goes on at much higher revs suggests either the water pump is not outputting all it should, or the obstructions are severe enough to affect sufficient flow.

So although there maybe blocked passages, the first would be to suspect the pump (they have a maintenance requirement).
Second would be to check thermostats (actually condition of passages around and behind, and testing whether opening properly in separate hot water container).
This is just in the order of probability, but both should be done regularly anyway.

[CTJackC!]

Great advise. My mechanic (at the marina) believes its likely just the water pump but it will be easy enough to take a peak behind the thermostats to check for blockages. I was somewhat ready to put money into a new engine but the fuel use difference between the 2 stroke and the 4 stroke does looks fairly minor. According to the literature the old 2 stroke gets 3.0 MPG at my optimum speed and the new In Line 4 gets 3.7 MPG. This is the first used boat i have purchased, I'm fairly religious at following maintenance schedules and the really sad part of this entire "story" is that the original owner had a heart attack and passed away in the spring. He helped me out in understanding what service he had done on the boat late last year when I discovered fuel system issues, which were a bit more extensive than I expected. I'll report back after some additional maintenance is completed.

Prior to this Yamaha I had 4 Evinrudes (all purchased new with adherence to maintenance schedules), and before that a mix of Mercury and Johnsons. Towed in twice (Evinrude). I've spent a great deal of time on boats with Yamahas (no tows on those boats).

An early Happy Thanksgiving to all.

Jack

[zenoahphobic]

I tend to think keeping a two stroke as long as you can. Their maintenance is less, they are relatively easy to fix. And it is sometimes argued, depending on the application, that they have more startup grunt.
Keep it unless you really want better economy, less noise and smell. Or you want a shiny new engine.
I 'll probably keep mine until I am arrested and forced off the water!

[CTJackC!]

zenoahphobic - very funny. Actually when I went for the sea trail there was small group of family members that fish Parkers and I was somewhat surprised with that it had a 2 stroke - they shared your viewpoint. Basic comment was you need the power from the 2 stroke to get the heavy Parker up and running. I actually love the engine, just need to get the alarm issues cleared up. I thought they were gone but at least they came back now versus the spring launch. Jack

[99yam40]

if you cannot do it yourself ,

at least have the mechanic test the alarm system while you are there to look at the gauges to see how they indicate what the alarm is that is setting off the buzzer.

draining the motor oil tank and then turning on the key should get that tested.
I think jumping one or both(at different times) overheat temp switches should cause the over heat to indicate.

at least then you will know what to look for

[99yam40]

where did the delet button go

[pstephens46]

To delete entire post? Don’t see it.

I think there is a time limit to delete text. Posts apparently cannot be deleted.