Overheating Alarm Problem

[stwaxy01]

First time on site. Hoping I can get some help. Thanks in advance.

I have a 2001 Yamaha C40TLRZ Outboard. Salt water use. Freshwater flushed every time. Non-ethanol gas.

Had throttle fully open. A 150 yards from slip I throttled down to close to an idle. About 50 yards or so later the buzzer sounded (steady buzz – beeeeeeeeeeeeeeeep). Engine ran fine but no stream from tell-tale(?). Let sit for a day. When I turned key once (not to start but just to get electric on) the alarm sounds immediately and doesn’t stop. A day later, same thing so thinking engine can't be overheated still. I drove the boat about a 100 yards from slip to ramp to get it out of the water (idle speed). Alarm sounded the whole time. The engine started shake about half way and continued. Still no stream from the tell-tale.

Bought/installed water pump/impeller kit as well as the exterior pump housing/cover (black plastic piece). Drained and replaced the lower unit oil. Hooked muffs up and engine was peeing strong but the buzzer continued to sound (even when I just turn the key one turn) and the outboard continued to shake.

I’ve read about 100 threads on this but not sure where to start, Poppit(?), thermostat, bad sensor, something else? One thing to note is that I never did take it back up to full throttle after the buzzer went off so not sure if it would go off or not once I did.

[stwaxy01]

To close the loop on this post, I pulled both sensors. One of the wires on one of the sensors was melted down to the wire (about 1/16" of wire exposed). In the short term, I used electric tape to cover the area and plugged them both back in. Alarm no longer sounded when I turned the key and engine no longer shook vigorously.

The solution was either pulling the sensors out which may have reset them and/or covering the exposed wire on the one lead to the one sensor.

[99yam40]

that is a strange problem as those wires should not ever see enough current to melt the insulation

[cpostis]

To close the loop on this post, I pulled both sensors. One of the wires on one of the sensors was melted down to the wire (about 1/16" of wire exposed). In the short term, I used electric tape to cover the area and plugged them both back in. Alarm no longer sounded when I turned the key and engine no longer shook vigorously.

The solution was either pulling the sensors out which may have reset them and/or covering the exposed wire on the one lead to the one sensor.

Stwaxy:
When you said "wires on one of the sensors was melted down", could it be from rubbing on the cylinder head? I don't believe you would ever have enough current to melt the wire? Is the wire pliable or stiff where the insulation is missing around the wire. 1/16" not much, I would probably just cover the area with adhesive heat shrink if the wire is still pliable.
Guys, I believe Stwaxy has everything connected and operating as should be, correct Stwaxy?

[stwaxy01]

Thanks for the follow up thoughts. Probably a bad choice of words (and from an inexperienced eye). Rubbed or cut away is a better description than melted. I didn't see any melted sheathing, just a small missing piece that looked like it may have been up against the head. The wires were still pliable.

Yes, as far as it seems to me, the overheat issue is resolved - no more alarm, tell tale is shooting water, engine doesn't appear overheated and not shaking vigorously anymore.

While triggered by overheating from a broken water pump, I assumed that since the alarm continued to sound even with engine off that it was an electric issue. And, I assumed taking them out and putting them back in served as a reset of sorts.

It may be worth me testing the sensors (or replacing them) to ensure they are functioning properly.

[zenoahphobic]

Thanks for the follow up thoughts. Probably a bad choice of words (and from an inexperienced eye). Rubbed or cut away is a better description than melted. I didn't see any melted sheathing, just a small missing piece that looked like it may have been up against the head. The wires were still pliable.

Yes, as far as it seems to me, the overheat issue is resolved - no more alarm, tell tale is shooting water, engine doesn't appear overheated and not shaking vigorously anymore.

While triggered by overheating from a broken water pump, I assumed that since the alarm continued to sound even with engine off that it was an electric issue. And, I assumed taking them out and putting them back in served as a reset of sorts.

It may be worth me testing the sensors (or replacing them) to ensure they are functioning properly.

You say "not shaking vigorously anymore". I was worried when in your first post that you continued to run the engine, no tell tale and "it started to shake about half way". Well that shaking could well have been the engine seizing up and persisting running the engine will no doubt cause internal damage.
So regardless, remember this history if you don't investigate if you have damaged it now, when some breakdown occurs in the future.

[TownsendsFJR1300]

Sounds like two issues.

First the WP or a clog in the water lines)
Second, your overheat alarm wire simply grounded out to the engine, shorting it (basically completing the circuit as if it was overheating constantly)..

The shaking, dunno, maybe it was super hot, spark plug pre-ignition, etc.

Sounds like your probably good to go.


Did your impeller come out as one piece or did it shred up?

Small, shredded pieces can clog up the pisser...

[stwaxy01]

That sounds like it Townsends.

The impeller was largely intact but the rubber part broke away from the plastic piece inside so it wasn't spinning at all. Separately and coincidentally, the short in the alarm kept the alarm on. For the shaking, I had read that the engine will do that when the alarm is on as a way to get you to turn it off so further damage won't be caused. Once I reset the alarm, the shaking stopped.

[TownsendsFJR1300]

That sounds like it Townsends.

The impeller was largely intact but the rubber part broke away from the plastic piece inside so it wasn't spinning at all. Separately and coincidentally, the short in the alarm kept the alarm on. For the shaking, I had read that the engine will do that when the alarm is on as a way to get you to turn it off so further damage won't be caused. Once I reset the alarm, the shaking stopped.

Never heard of that before(the WP separating as such, nor the shaking from the alarm)!!!

Your actually lucky it didn't send little rubber parts and clog up the cooling system (Major PIA)...

Great info, tks for posting..

[rodbolt17]

not the first hub separation I ever saw.
yes the motor will shake like a dog passing peach pits when RPM reduction is set.

[99yam40]

I thought that some of the small motors retarded timing instead of miss firing spark plugs in RPM reduction.

am I wrong with this?

[99yam40]

Never heard of that before(the WP separating as such

I have only seen one that did that, but it was one that had not been replaced for many years.

Most just shed pieces of vanes

[TownsendsFJR1300]

I have only seen one that did that, but it was one that had not been replaced for many years.

Most just shed pieces of vanes

Yep, that's what I've read here..

Years ago, for S&G's, after replacing my WP impeller(or course it's much thicker), I tried cutting / hacking up a vein, just to see how well it held up (and it did have a "set" in it)...

That SOB was TOUGH!!, Short of taking a really good good set of cutters to it, or busting your tail with a sharp razor blade, that thing was NOT coming apart.

I guess the smaller ones aren't nearly as robust or maybe run dry more often.. But the larger ones, if one comes apart, jeez, don't know how you'd do it...

[pstephens46]

not the first hub separation I ever saw.
yes the motor will shake like a dog passing peach pits when RPM reduction is set.

Never heard that one before!

[zenoahphobic]

Never heard that one before!

I presume that's the dog trying to pass the large seed. Video please!