Toahtsu MFS25B suspect cooling

Hi,

I've got a Tohatsu MFS25B, I've started to get problems this season.
It started with the alarm / red light after running at cruise power for 5-10 minutes, it reduced engine speed to idle automatically.
I've having problems finding the solution to my problem, the following has been done without fixing the issue in accordance with the troubleshooting guide in the servicemanual..

- Replaced impeller, and rechecked fo correct installation.
- Replaced engine oil and filter.
- Functional checked thermostat, opened fine at correct temperature.

One thing I did notice today after eingine oil replacement, was a flow of coolingwater (cold water) flowing from an opening in the lower part, just by the two mounting bolts for the tilt with rubber dampers. See video on youtube.
Is it suppose to be like this? the cooling water check port has waterflow as normal.


Any suggestions?

edit: it's a modelyear 2012, Serial: 004788AB

Never change just the impeller; do the complete wp kit -- works better and lasts longer.
What oil are you running, and is it below the Full mark on the stick?
That is a drain, and is normal. That's the cooling water going out the exhaust.
Have your dealer connect you to a laptop and read out the ECU to see what it has to say.

pvanv said:

Never change just the impeller; do the complete wp kit -- works better and lasts longer.
What oil are you running, and is it below the Full mark on the stick?
That is a drain, and is normal. That's the cooling water going out the exhaust.
Have your dealer connect you to a laptop and read out the ECU to see what it has to say.

Click to expand...

The WP kit is at bit expensive to replace everytime I would have changed the impeller (in norway these things costs alot), all the parts seemed to be in good condition. The old impeller was quite soft, was able to see the difference in waterpressure with the new impeller.
I'm using a 10W-30 FC-W certified, synthetic blend oil, filled to the upper mark of the dipstick. Roughly.

I guess the next step will be to bring it to a dealer and have them do the diagnose of the ECU.

We had the 30 hp version of this motor (six motors, 2010-2016 model years) before we got sick of all the defects (poor cooling, cracked oil pan, head corrosion, engine mount failures). About the only good things are fuel economy and availability of the diagnostic cable to private owners.

It's easy to re-install the lower unit without a good seal between the water pump outlet and the cooling water riser tube. It's also easy to ingest crud that will block the riser tube. Once the cooling water flow diminishes, the head overheats, the paint on the head gasket flakes away, and corrosion eats through the head right by the exhaust valve, because it's where stainless is right by aluminum in salt water with plenty of heat.

To keep this motor running for all the maybe 500 hours you can get from it, check the cooling system very very carefully during service, and replace the internal anode in the block. You might consider changing the head gasket, too, before the paint flakes off it. Changing the water pump as a kit will do nothing if you don't have a good seal at the connection to the riser pipe, or if there are bits of seashell blocking the riser pipe.

We switched to the Etec. No stainless steel head gasket, and way more flow through the cooling system.

Really?
If someone is so ham-fisted that they don't re-insert the water pipe into the wp grommet, they should not be working on outboards. Period.
If an idiot then continues to run while overheated, they should not be running outboards. Period.
If the strainers are installed, it is impossible to get anything into the water system that would clog it.
No, the exhaust valves are not in salt water, so there is no electrolytic corrosion issue. If overheating, all bets are off.
The Tohatsu MFS25/30B/C also gets re-badged as Mercury motors; They don't have any such reports.

My customers have several of these motors with thousands of hours on them. All still start and run like new.
Yes, just like any outboard, the anode needs regular service. Same for the water pump, and the OP concluded that a new impeller made it pump stronger.
Just don't overheat, and you won't have head gasket damage. Why on Earth would you change a good gasket? That is just nonsense.

The ETec is a fine bit of 2-stroke engineering. Not as cool as the low-pressure TLDI. With its extreme pressures, requirements for exceptionally-expensive DFI oil, and the requirements that any ETec needs to be setup with a laptop. Of course there is the very high price as well.

This post was from August 1st, and there has not been any follow-up since August.
What kind of troll is trying to bad-mouth a product on that product's page?
Maybe better to praise the ETec on the Evinrude page.