So I just bought a Mac X....

[Tomfoolery]

Have you determined that the temperature sensor is actually ok? Infrared thermometer reading at the sensor support the overheat signal?

Seems like someone mentioned the sensor earlier, but I can't remember if you've been able to verify it.

If this is the right thread, I believe the procedure for checking the temperature sensor was in one of the pages from the manual that I posted earlier. And I agree - it’s an easy thing to check, so it should be checked to verify the integrity of the sensor and to eliminate it from the pool of possible causes of the overheat alarm.

[Drifter]

I haven't checked it but the fact there's a used one in the box of parts suggests that the previous owner has already tried that route

I have an infrared temp gun, but if I trust it to be accurate is a different matter...

I'll re-read how to check

[OverEasy]

A regular old thermometer into the peestream gives a fair assessment too....

[Drifter]

Opie showed a page with a wiring diagram but I'm not sure how to actually test the sensor from that? (Edit: it does show how to test it in hot water, but read on...)

Actually looking at that image, I'm now not so sure the switch I have is actually that. Mmm. Let me go get a photo of it...

Welp! Now I'm really confused...



OK, in the tub of parts that I found buried in a compartment (weeks after getting it!) I found a switch. I'll attach a photo. I was 100% convinced it must be the temperature sensor, as there is one similar, I think, below the thermostat. Let me load the pic from my phone...



I didn't have long-nose pliers handy to pull the electrical connection thingy off but I'm pretty sure that this is the same as that below the thermostat.

HOWEVER, when I went to look at the engine just now, I realized that the thingy there, and the thingy in Opie's picture, don't look the same. Also it's below another sensor or switch directly below the thermostat (the white one is below that) so I found a 24mm socket and was able to unscrew that other sensor...



But I think that is perhaps an oil pressure sensor? Because that had engine oil, not water, come with it. Just a dribble, thankfully.

Now it gets even more confusing, because going back to Opie's manual pic, it looks like the switch should go in the empty hole, which, you know by now, is below the thermostat?



But that's just a blank hole on my engine. There's no thread, it doesn't go anywhere.

Also, the thing shown in the manual doesn't look like either of the 2 I have found/pulled out.

Seems a stupid question to ask "Perhaps this version doesn't have a temp sensor?" because the over-temp alarm is the issue, so obviously it's getting a reading from somewhere.

Perhaps that manual pic is just not clear and is pointing to something else? Can anyone else peer at their BF50A circa ancient, and see if they have a sensor there? The manual shows a thread and a torque reading, so it's not just meant to plug in a smooth hole.

[Drifter]

Uploaded another pic. Looking closely, it's clear this is a factory blanking plate.

Which is weird, because this is an early engine. I can understand blanking off a hole no longer used, but it doesn't make much sense that they'd blank off a hole they were going to use in the future?

Anyway, it does seem this engine has a temperature sensor hiding somewhere else On the other hand, I don't think it's likely that the sensor is the problem, as a faulty sensor would either sound the alarm all the time, or not sound the alarm when it should do, right?

That the alarm doesn't sound at low revs but does when pushing hard, then goes off again at lower revs, would suggest that sensor is working as designed.

Right?

[Be Free]

I'm going from memory here so I'm open to correction...

There should be two sensors on the port side of the engine. The top one is the temperature switch and should have a single yellow wire. The bottom one is the oil pressure switch and has two wires. I don't remember the colors for that one.

[Be Free]

There is only one buzzer for audible alarms but there are two switches that can set it off. The temperature switch and the oil pressure switch are both connected to it. You need to look at the lights on the remote control to see which switch is actually setting the alarm.

Neither of them are directly aware of the engine RPM but RPM can affect what they are measuring. Low RPM + bad oil pump = low oil pressure. Any RPM + bad water pump = high temp (eventually). Once the engine is over heated you are going to get an alarm regardless of RPM.

I know we've been discussing this problem for a while but are you absolutely sure that the alarm you are getting is high temp and not low oil pressure? Have you checked the lights on the remote when the alarm is on?

I don't think this applies to you but just for the sake of anyone reading this thread later you can get the alarm if the engine is tilted up too much. The engine tilt angle is sensed from an arm on the engine mount connected to a rheostat. I've also had the alarm go off if there was a problem with the ground wire between the remote control and the engine. Both of these would have the alarm go off continually. That's why I don't think it applies to you.

[Russ]

I still say take it out for a spin with new impeller and t-stat and see what happens.

Flushing it can't hurt either. Probably needs it anyway.

Is that electrical tape on the yellow wire? If so, why? Could that wire be grounding and causing the alarm? Or is the tape just to prevent chaff?

[Tomfoolery]

Have you checked the lights on the remote when the alarm is on?

And for completeness, when oil pressure normal, the green oil pressure indictor is lit. This should always be showing green when the engine is running. If it's not, the alarm will sound.

The high temperature light, which is right next to the oil pressure light on the remote console, does not light unless the temperature is excessive and the audible alarm is making noise.

My manual shows a yellow conductor to the temperature switch, and a single red conductor to the oil pressure switch. The OP's photo does appear to show two wires to the oil pressure switch. I'd have to go to the boat and pop the hood to see what mine looks like.

[Drifter]

I haven't seen or noticed any lights on my controller?

I know the previous owner claimed the overheating alarm would come on at high revs, which he said was due to his fitting a 4 blade prop and he didn't change it as he was happy to go slow.

So I changed the prop back to the original 3 blade - but at high revs, get an alarm, which cut the revs down to idle. I'd guess if anything, a low oil pressure alarm would kill the engine entirely, rather than let it idle without oil?

So yeah, I'm sort of presuming it's a temperature alarm - and the pile of thermostats and impellers suggests the seller knew it was not the propeller - or maybe not. Maybe that was the original owner and the last owner just didn't do any servicing? He was kind enough to put those spares in the boat anyway.

I have heard of lights with the Honda. I'll take another look and see if I have any... OK, found a pic I took early on; i'm guessing the top one is the temperature light?

I get the impression someone has changed the angle of my controller, as it seems very low. If you're standing up you have to bend right down (or sit down) to use reverse. And while standing up I would not really be able to see those lights at that angle. Indeed I didn't notice any light when the alarm went off. I didn't know I had any!

I'll take a look tomorrow, see if the green light comes on when it's running.

This pedestal is looking better than it did but I do want to tidy it up and make it prettier. Perhaps find a rubber to replace that gloopy stuff. I don't mind the gloop inside a rubber but it looks pretty awful

[Tomfoolery]

Most of those Honda remotes are mounted that way, with the thumb button for tilt/trim on the outside. It's pretty poor, but it's the easy way to mount it. I flipped my handle to the inside and mounted the remote on stand-offs, and rotated it so it's 'level' and I can see the lights, but that's another thread.



I shoulda reduced the pic before putting the red oval around the lights - can't hardly see it.

[Tomfoolery]

Drifter, let's ask Tomfoolery to reinstate his photos in his old link here

viewtopic.php?t=23259

The springs are for the tilt lock.

Photos have been updated.

[Be Free]

My remote was mounted with the key on the bottom, 90 degrees from the way Honda intended it. I modified it to be horizontal but never liked the way the cables had to be run in that position so I put it back.

Drifter, those are the lights I'm talking about.

For "extra completeness" the over-rev alarm sounds just like the overheat alarm but does not turn on any lights. Since he's never checked the light it is possible that it's been an over-rev alarm due to being under-propped or perhaps a spun hub.

[Drifter]

No major developments today, but I did start the old lady up, and...

...

I was thinking "Well that could be a problem, as there's no green light" but yeah, if you really twist your neck around and peer closely, it's there.

Oil pressure is a GO!

Weird thing. Decided to remove the grab handle from the top of the engine hood, sand it a bit and spray it gray. Did so - but while getting at the bolts underneath, spotted this...

Is that a date, in English (Arabic) lettering?






And some Borneo caterpillar thingies? For local interest.


A3-03-04

Or maybe H3--03-04?

If that's the year 2004, and the engine is original to the 1996, then that's 10 years later. The date of a major overhaul?

I doubt anyone would write in such big letters if just the date of a service? Or is it even a date?

[Be Free]

Great news on the oil pressure.

Turn the key on and short the wire going to the temperature sensor to the block. See if the over temperature light and alarm comes on. You should get a red light on the remote and a steady alarm. That will tell you if the bulb is good.

Were you able to get the alarm to sound when you were running it in the tank earlier or only when you were on the water?