Overheating Outboard

[tryhard]

Morning all,

New member looking for input from experiened Outboard users.

I have a Suzuki DT85 mid 80's I think, that's just been serviced.

On the river on Sunday did a 10 minute run mostly at WOT - engine ran fine.

Fished for about 2 hours, then on the run home after about 5 minutes at WOT Over temp alarm sounds and engine stalls.

I left the leg in the water and peered over to see if there was any rubbish around the leg, there was none, and the telltale was pumping plenty of water before she died.

given that before going on the water I ran the motor on the ear muffs for about 15 minutes with no probs, i suspect something like a faulty thermostat.

Anyone had similar problems and is it wise to run an outboard without a thermostat ?

Any input greatly appreciated

thanks

[chrisg]

tryhard

thermostat is certainly the first place to look. you can run the motor temporarily without it...the motor won't reach temp in theory so if you still get overheat it indicates something deeper. Check theres no shell grit or something jamming it. How long ago was it serviced...you or a mechanic? If very recent I would be taking it back.

Cheers

Chris

[tryhard]

tryhard

thermostat is certainly the first place to look. you can run the motor temporarily without it...the motor won't reach temp in theory so if you still get overheat it indicates something deeper. Check theres no shell grit or something jamming it. How long ago was it serviced...you or a mechanic? If very recent I would be taking it back.

Cheers

Chris

Chrisg,

the motor was serviced about a month ago by an authorised sevice centre.

I have spoken to them since the incident and they said it could be a number of different things such as blocked (corroded ) galleries, failed thermostat or failed exhaust gaskets.

I would take it back, but at this time of year, I have no show, and I want to use it over Christmas, so I've ordered a new T/stat any way at least thats the 1st step in identifying the problem, and something that I can do over the break.

thanks

[njsconst]

Morning all,

New member looking for input from experiened Outboard users.

I have a Suzuki DT85 mid 80's I think, that's just been serviced.

On the river on Sunday did a 10 minute run mostly at WOT - engine ran fine.

Fished for about 2 hours, then on the run home after about 5 minutes at WOT Over temp alarm sounds and engine stalls.

I left the leg in the water and peered over to see if there was any rubbish around the leg, there was none, and the telltale was pumping plenty of water before she died.

given that before going on the water I ran the motor on the ear muffs for about 15 minutes with no probs, i suspect something like a faulty thermostat.

Anyone had similar problems and is it wise to run an outboard without a thermostat ?

Any input greatly appreciated

thanks

Tryhard,

I had what sounds like an identical problem with my outboard a few years back now.

I will bet my left nut that it is a block head. You get a build up of salt over the years in the top of the head that flushing just doesn't seem to clear out. No fault of yours, I always flushed my motor for ten minutes after every use and it still got me.

The build up of salt prevents cool water getting right up into the top of the head to pull the heat off. You can run your motor at normal operating range without any probs, but as soon as you go full full throttle or push it a bit...... it will overheat every time.

What it did to fix it was firstly change the thermostats, they are very cheap ($30 pair) and don't run your motor without them! Change the water pump impellor, also very cheap ($40). That will elliminate the two most common casues of overheating. Even though there is water coming out of your tell tail that does not mean your water pump is OK. The only way to guarentee that your water pump is OK, is to pull it apart and inspect the impellor. It is not as hard as it sounds, you drop the leg off and the impellor is on the lower half of the leg under a small housing held tight by 4 nuts. If the impellor has de-laminated from the plastic sleeve

the impellor will still spin and pump water out of the tell tail. But it will not be spinning at the same rate as the drive shaft, therefore the water pressure will be alot less and not pumping cool water right up to the top of the head where it is needed.

Once you elliminate the thermostats & impellor, it will confirm that your problem is a build up of salt in the top of the head. This is fixed by simply pulling the head off, clean out the build up and then replacingit. Depending on the extent of the build up the head may need to be sand blasted. To do this job you need to replace gaskets and torque all the nuts to the right setting. A job left for the experts.

Good luck.

Nathan

[tryhard]

Nathan,

thanks for your input.

Just so you know, the impeller was replaced in the last service (the service guy indicated that it was not in that bad a condition - I wanted it replaced to be certain.

You refered to T/stats plural - am I missing something here ?

If the head is choked up, is it possible to back flush ?

or, is there a product that I can run through the system to break down some of the build up ?

I am not keen to pull the head at this stage because I want to nurse it through Chrissy so I can take the kids out & maybe try to catch a fish.

With my luck I reckon I could break a handfull of bolts which would really add to my Christmas spirit, particularly as I wont be able to get any parts, or any one to work on it until some time in mid to late January!!

[jjsydney]

Hi Mate

I use a salt away product wihch helps to dissolve the salt that builds up int eh gallerys, not sure how well it will work if they r seriously choked up but I have found that it has keep the gerneral salt build up all over the boat riht down.

Jon