o/heating on 115 Yamaha

[redbloke1956]

Hi to all, was wondering if any one could tell me if stale fuel....5-6 months old could cause overheating warning buzzer to sound on a near new 115 Yamaha two stroke?
Thanks
Redman

[wessel]

Have you checked out your cooling system?
In what conditions was the boat stored i.e. under covers or did the engine receive direct sunlight ?

In Aus you guys have bugs that have this tendency to crawl in everywhere and make nests where they can. (My first night in Australia a couple of years back I sat down on a huntsman's spiders nest that was just hatching. I had hundreds of little spiders all over me:o)

Secondly, when did you last change the impeller? If it has stood for a while and you dry started it before putting on the muffs or in to the water, then there is a good chance you may have damaged some of the vanes on the impeller.

But the fuel itself should not cause the engine to overheat.

Wessel

[Noelm]

yep, the chance of stale fuel causing an overheat is pretty remote I would say, more likely water pump dead/fried/broken from no use

[redbloke1956]

Hi Wessel , thanks for the reply...cooling system should be good, motor only done about 40 hrs...plenty of water from telltale, was running with muffs on, never done a dry start/run, motor almost always covered by the oversize boat cover, BUT ....had trouble (couldn't) trying to fill half full tank at servo half hour later...tank has two vents but would not take fuel.....maybe a vapour lock somehow?

[flotsom]

fuel will not cause overheat alarm, i have seen so many motors overheat on flushers, even when the owner says that there was plenty of water pressure and tell tail was good, take to boat ramp, run in the water even without taking boat of trailer and see if problem is the same.

[Kerry]

No

[Chimo]

Hi Redbloke 1956

I had an overheating problem too in a V4 that occurred, I think from new, and I only just fixed after getting sick and tired of it happening.

Mine was predictable, I could make the buzzer go off when ever I wanted and I could avoid it just by the way I drove the boat.

Your 115 is a V 4 too isn't it.
When does you buzzer go off
Have you felt the heads when it happens
Is one hotter the the other
If you swap the thermostats does the same thing happen presumably in the same head

PM if you want to hear the full story of mine and maybe what could be an issue to look at.

Cheers

Chimo

[HarryO]

G'Day Redman.

What model izzit?

Chimos on the money. Check your thermostats first.

On the leg, at the rearmost part of the casing right
above the cav plate there is a set of vents...

Start the engine, get it up to operating temp, (if you can)
and observe if any water is exiting from these vents.

Lift the revs to 1500-2000 rpm for 10 seconds or so and
observe it again. repeat...

If you cant see any water coming from these vents,
then your poppet valve is sticking...

Common cause of overheat alarms sounding when all else
appears operational...

[Kerry]

This should not be a thermo problem with a "near new" 115? How new is "near new" but sounds like it needs to go back to the dealer and tell them to make it right!

[HarryO]

The overheat alarms are situated right next to the
thermostats at the top of each head.

It doesn't take much to set em off.

A stick / faulty thermostat will do every time.

Harry.

[Kerry]

Harry, Yes but just how "near new" is this engine? Thermostats, head gaskets, water jackets, valley cover gaskets and associated galleries would be the obvious choice after a few years. Bung heat sensor? These can easily be checked in a pot of water. #

Similar with thermostats in a pot of water BUT how old is this engine first?

[Chimo]

Hi Red

Youve not answered my questions but heres a few more for you

When you tested the first stage operation of your thermostats by pouring boiling water over them while they were in a container did they open ok
No then you might have found something BUT

IF Yes they heres the next important thing to consider.

Do the thermostats function correctly in their second stage operation
???

This is the tricky bit ::) :( So you need to be on board to sort this out ;)

I'm off for a coffee now so later :P

Cheers

Chimo

[HarryO]

Hi all..

The heat sensor (alarms) are a simple
canister with the internal contact to earth
insulated in wax...

As it gets hot, the wax melts, and contact is established.

They can only handle so much heat so often, and they'll need
replacing.

And they're NOT CHEAP.

As Chimo said, while the engine is warming up,
place both of your hands on the heads near the top.

They shound not get so hot so you can't keep your hands
on them.

If the alarms go off, you can pop the alarms out
while you are diagnosing....
don't let the engine run too long like this in case there are
more sinister problems lurking.

What year / model is this?

[redbloke1956]

Hi again to all, sorry about late response, am having computer dramas now...one of those weeks >:(.
Thanks to all that responded...bit more info then...the motor is only about 12 months old and has done about 40 or 50 hrs....(moved house...new partner etc so little use till now)..hasn't seen water in about 5 months either.
The boat and motor are normally under a tarp type cover also.

I turned off the motor as soon as alarm started, waited for a while and restarted it...sounded like it was running on 3 cylinders so turned it off straight away.

[Spaniard_King]

get it to a dealer ASAP, sounds a bit terminal.

BTW I bought an ifrared temperature gun for these problems, makes OH problems ever so easy

Garry

[Chimo]

Hi Redblke 1956

I too think like Gary that the dealer needs to get involved asap

The running on 3 cyclinder thing could however have been the motor rev limiter working to keep you from loading it up and doing any damage.

I had a similar thing with mine which had a similar problem more or less from new that the dealers never resolved but with some input from a few techs both here and in the US I finally sorted it out.

Have you checked the thermostats in a saucepan of hot water. You can pour boiling water on to them or you can slowly heat the saucepan with both thermostats in the pan and watch what happens.

As I said earlier, if they both open that resolves part of the thermstat issue.

If the second stage of cooling water flow of you motor is as I think it may be; then the entire thermostat needs to be able to move to provide the primary cooling water flow at hot / high speed operation.

If they, both thermostats, don't operate in unison re water flow there is likely to be a very good flow on one side and a defficient / low flow on the other. This can lead to a significant overheat on the one side that will cause the rev limiter to make your motor seem like its running on 3 cyclinders and even if you try you can't get it to rev; this is as its supposed to be.

You probably have not run the motor but if the termostats work ok when tested its possible to get an idea of the likleyhood of your problem being what I'm guessing while the thermostats are out of their housings.

If your going to take the housings off there is likely to be two spots to use a spanner, one large one small, go the large even with a big shifter as your a lot less likely to break the thermostat cover if you gently work it with the bigger grip on it.

If you go the dealer route before doing any of this PM me and I can suggest to you what to look for when the thermostats are out.

Either way please let us know what you find out.

Cheers

Chimo