[ducksniper]

Hello all. I know there are some folks are here far more knowledgeable than I.

I have a 25 HP four stroke Tohatsu 2004 outboard. When running for an extended period at a slow speed interspersed with idling (setting and checking limb lines), it will choke down and cut off. Once it does, it will not crank for probably 10-15 minutes. It fired up Saturday within seconds so the motor is good to go. After the 10-15 minute period, it cranks with no problem.

Possibly shuts down when running too hot? I'm getting water discharge so I question that is the case. Water pump was replaced about a year ago.

Any thoughts on what's going on and what I can do about it? Thanks in advance.

 

[mikeski]

A couple things are....

Vapor lock in the fuel system
Ignition coil is failing and works when cold but then starts to fail when hot.
Other ignition parts.

You can try to spray some starter fluid in the intake when it will not start. If it tries then it's probably fuel if it still does the same thing it's an ignition part.

mikeski

 

[sundrop]

"Other" end of the coin might be a sticky injector or bad sensor. Might be over fueling and loading it up choking it out. After it its and dries out it cranks.

 

[mikeski]

Sundrop is correct. I have not seen the inside of a 4 stroke outboard enough to know all the tech they have in there.

In a car there are a couple of sensors. There is the crank and cam position sensors that could be going bad. If it can't tell the position of either it will not start.

Are there coil packs on that like my two stroke? Or is it a standalone coil?

You can go to a computer shop or maybe Radio Shack until it shuts down and pick up a can of cold spray.

When it fails troubleshooting can be to

Take out a plug and see if the plug is wet with gas.

Spray each sensor one at a time with the cold spray and see if that fixes it.

mikeski

 

[NeuseRvrRat]

As stated above, my two guesses would be either a coil that fails once it warms up or something hanging up with the fuel system and flooding it.

 

[Brian the boat guy]

Is it a carbureted unit or fuel injected? What year?

 

[sundrop]

Its also possible it is sucking or pinching an old fuel line when it heats up. I think 2004 was injected right? But Tohatsu uses a lower pressure injection system unlike other manufacturers, Supposed to save fuel by better atomization of less fuel. .

 

[Brian the boat guy]

The reason I was asking year had to do with the fuel line. Good catch sundrop. But also too had to do with the pre-ethanol lines we had. If you have a 2008 or prior line I'd suggest seeing your nearest dealer with regards to new lines. If you have blue colored print in your lines they are the newer technology. Red print or something else....you may be susceptible to interior breakdown which means for lack of a better term "fuel line chunks" in your gas going into your injectors.
Also too, loss of juice (gas) to the engine could be attributed to something as simple as a $20-25 fuel bulb that's cracked or has a small hole allowing air in. Try changing that out.
For the least expensive route try a little Lucas Oil ethanol treatment and some injector cleaner. Great stuff, low cost.