Help please - New Yamaha F2.5 overheated and completely wrecked

[JasonSSD]

I'm hoping someone might be able to suggest reasons for this new engine overheating.

Bought new from dealer in 2022, run for 7 hrs ok. Then serviced by dealer last winter (to preserve warranty etc) and 1st trip out this year run for approx 45 mins before stopping - permanently!

Coolant water was running when started & visible during the 45mins of use. No weed or plastic bag etc was found when engine stopped. Water pump & tubes / pipes were all completely clear when checked later by dealer. However engine had clearly massively overheated - melting the yellow dipstick, thermostat, electrical wiring and more. Total right off.

From the outset (before even opening the engine up) the dealer was making out it must be a weed / bag blockage. They looked less confident when internals proved to be clear. They sent photos & commentary to the official Yamaha tech advice line, who after asking a few questions have simply stated since there's no blockage and the dealer can't explain the overheating then it's not covered by warranty & not their problem. Seems like a classic "catch 22" to me - no blockage = deny liability, yet if there had been a blockage it definitely wouldn't have been covered!

I suppose what I'm really asking is:
1. Does anyone out there know of any other possible explanations / reasons why the engine would have overheated so catastrophically? (apparently the water pump & impellor were fine).
2. Shouldn't the engine have stopped (triggered by the thermostat?) well before such high temps were reached to do so much damage?
3. Is it reasonable for me to expect Yamaha's warranty to cover this, or for them to at least show good will?

Just for context - I've been using outboards of various sizes (mostly Yamaha) for 40+ yrs and whilst I've experienced weed / rope / debris wraps on occasions I've never seen anything like this, and certainly not written off an engine.

Any and all comments / suggestions would be very welcome.
Thanks, Jason

[neil.mccrirrick]

Is there oil in it? Check the oil filter for metal/contamination

[JasonSSD]

Originally Posted by neil.mccrirrick

Is there oil in it? Check the oil filter for metal/contamination

Hi Neil, yes there was oil in it - however this (and I believe fuel) were clearly leaking from it soon after it stopped. I can head into the dealer tomorrow and check the oil filter (it's there for them to do "further examinations")
Many thanks for the suggestion

[Pikey Dave]

Does the engine have any built in overheat protection? If so, it’s clearly failed & therefore should be a warranty job, irrespective of how the overheat occurred.

[chipko]

Ouch! That’s unfortunate.
If strongly pumping water at the time and oil level all okay, then had the thermostat stuck closed? Assume dealer would have inspected that as a potential culprit. Not a service or inspection item at those hours, unless gunged up with salt deposits, so no warranty get out.
PS No oil filters on these splash lubrication motors as far as I recall.

[Poly]

Could it actually have had a small fire? To get hot enough to melt all that before you noticed it had to get from running warm to massively overheated very quickly.

I'd want to sent it to Yamaha themselves to inspect (and if I worked at Yam I'd want to know what caused it). I wouldn't want the dealer that did the service doing the inspection as it is not in their interest to find any fault with the service.

Once you have an official response from Yamaha themselves seeing it - you'll be in a position to consider a small claims action against the dealer that sold it to you for it not being fit for purpose. I can't see a downside to pursuing that if you are 100% sure you used it right and there was no external obstruction etc. Costs are not crazy if court decide against you - but good chance that presented with a claim a dealer will settle or persuade Yamaha to do a deal on a replacement.

[beamishken]

It wouldnt be the first time someone picked up a plastic bag which blocked the cooling water intake which subsequently fell off once the engine stopped & drifted way before being noticed.
Otoh thats one serious overheat & you'd expect some piston & bore damage to create that much heat you'd also expect it to have been close to or to have actually seized which would have done internal damage. My other thought is too much oil in the crankcase of small engines can cause heating as the extra resistance of the oil causes the engine to work too hard & the oil retains the heat which could be the case here

[Davie]

I have seen this twice. Both times the passage between the 6 intake holes and the waterpump was half blocked. You get a tell tale and enough water that the waterpump does not burn but not enough flow to cool the engine. Did the throttle jam because the cables melted???

I will find pics

[Daibheid]

Originally Posted by beamishken

It wouldnt be the first time someone picked up a plastic bag which blocked the cooling water intake which subsequently fell off once the engine stopped & drifted way before being noticed.

I think this is the likely problem, a plastic bag or piece of weed of only a few square inches is all it takes to completely seal off the water intake. It could have stayed in place due to either/ or the pump suction or being draped each side of the lower unit and held there by forward motion. Once the engine quit, both forces disappeared along with the blockage and the engine being raised would have further tended to dislodge that kind of blockage.
The engine should have an overheat/low oil warning but these are often hard to see or hear, especially on small engines.
Sadly I think it's just real bad luck.

[JasonSSD]

Many thanks for everyone's comments and suggestions, much appreciated.

[Trello]

Originally Posted by Davie

I have seen this twice. Both times the passage between the 6 intake holes and the waterpump was half blocked. You get a tell tale and enough water that the waterpump does not burn but not enough flow to cool the engine. Did the throttle jam because the cables melted???



I will find pics

I read this and it didn't make sense to me: surely it would make sense to have the water coming out at the tell tale to be DISTAL to the flow around the cylinder - in which case if there was a reduced flow around the cylinder, it would show up (if you were looking for it) as an impaired tell tale flow.
But I've just looked at the diagram for my own (Suzuki) cooling circuit, and, sure enough, you could get a strong tell tale with no flow to the cylinder.
Why would it be designed like that? There must be a good reason...