Tohatsu 70 TLDI Temp Alarm

[JAGwriter]

Tohatsu 70 TLDI
Temp alarm after a ten-minute high-speed run yesterday.
Flow alarm first (mid RPM limited), then temp alarm (Trolling RPM only).
Does that every time now, about a minute after start.
I pulled the cover and the block temp didn?t feel that hot.
Cooling water flow is normal, but it feels cool, which leads me to guess that cooling water is not flowing through the block.
But I thought the pee-stream output was at the end of the cooling water flow and indicated the water pump was operating normally.

 

[pvanv]

Re: Tohatsu 70 TLDI Temp Alarm

Nope. The telltale only shows that the system is pressurized.

 

[JAGwriter]

Re: Tohatsu 70 TLDI Temp Alarm

Nope. The telltale only shows that the system is pressurized.

Thanks Paul. That wasn't the answer I expected.
Since the water pump is working, the cooling water path through the block is apparently clogged up.
Do Tohatsu's have a thermostat, which could be stuck closed?
If not, I've got to figure out how to find the piece of crap that caused the blockage.
But first, I think I should get a repair manual.
Do you know if the Nissan/Tohatsu manual that iboats sells is a good choice?

 

[pvanv]

Re: Tohatsu 70 TLDI Temp Alarm

If an old impeller lost a vane, that could be jammed in the block somewhere... or a bit o' junk or salt/silt might have made its way in. Yes, these are thermostat-controlled cooling systems. If it were to fail (not often), he stat would usually fail open, causing you to run too cool. The stat is at the top of the cylinder head. You can use an IR thermometer from the hardware store or cooking wares shop to read temps around the block.

I never recommend aftermarket manuals for any brand. They tend to be too general, and cover lots and lots of models. For a Factory service manual that is specific to your motor, you need to get a real Tohatsu/Nissan manual from your dealer. Do you have an MD70B?

The TLDI has a lot of data that gets stored in the ECU. Using the manual as a guide, you can put the motor in diagnostic mode, and read out the memories, in addition to a lot of other information. Your issue could be a simple as a blockage, or for that matter, could be a faulty temperature sensor... or it could be something else. The onboard diagnostics can help you a lot, and you will want the manual to guide you through the procedures.

 

[JAGwriter]

Re: Tohatsu 70 TLDI Temp Alarm

If an old impeller lost a vane, that could be jammed in the block somewhere... or a bit o' junk or salt/silt might have made its way in. Yes, these are thermostat-controlled cooling systems. If it were to fail (not often), he stat would usually fail open, causing you to run too cool. The stat is at the top of the cylinder head. You can use an IR thermometer from the hardware store or cooking wares shop to read temps around the block.

I never recommend aftermarket manuals for any brand. They tend to be too general, and cover lots and lots of models. For a Factory service manual that is specific to your motor, you need to get a real Tohatsu/Nissan manual from your dealer. Do you have an MD70B?

The TLDI has a lot of data that gets stored in the ECU. Using the manual as a guide, you can put the motor in diagnostic mode, and read out the memories, in addition to a lot of other information. Your issue could be a simple as a blockage, or for that matter, could be a faulty temperature sensor... or it could be something else. The onboard diagnostics can help you a lot, and you will want the manual to guide you through the procedures.

Yes, I have a 2007 MD70B, and this is the first problem I've had with it. I run it in salt water a lot, but always flush it with a hose using a clamp-on rig, usually right away but always within 24 hrs. The 'telltale' always got too warm to comfortably touch for very long until this temp alarm started, now it's not even slightly warm.

Thanks for confirming my doubts about aftermarket manuals. I always get factory shop manuals for my vehicles.

I really appreciate your help and advice.