Tohatsu 8 hp help

[hhboat]

1st time poster here. I am in a bind after a very rocky start to my season, and there seem to be some knowledgable folks in this forum.
Any help or ideas appreciated.

Tohatsu help.

The Saga that is my sailing season continues.

3 year old Tohatsu 8 hp. Ran fine in a tank at my house pre-season. I transported it to the coast in the correct position.

Still starts easily and runs perfectly smoothly, now that the boat is in the water. Had I not opened the throttle while on the mooring, I would have never suspected a problem.
Give it a minute amount of throttle, and it responds appropriately, with a slight increase in idle. Give it any more, even very gently, and it dies.

My first thought was air starved/ bad air filter. Or, less likely, not able to draw enough fuel because of a kinked hose, fuel filter, etc. I no longer think that because:

• I disconnected the tube running from the filter to the carb- no change.
• I briefly disconnected the fuel line between the carb and the filter, allowing it to run on what was in the fuel line for a bit- no change.
• And, if I pull the choke all the way out, it runs like it is nearly WOT. RPMs will increase slightly if I am full choke and give it some throttle.

All of the external linkage seems to operate smoothly.

My next thought is to pull the air filter, and to spray carb/choke cleaner directly into the carb, in the hope that there is some internal linkage sticking.

Anybody out there have any other thoughts?

 

[JB]

Re: Tohatsu 8 hp help

Howdy, hhboat.

:welcome:

Need a model number. 2 stroke or 4 stroke?

Sure sounds like plugged up high speed circuit in the carb.

 

[nyx2k]

Re: Tohatsu 8 hp help

i agree, gunged up jet in high speed circuit is likely cause and not restricted air flow

 

[hhboat]

Re: Tohatsu 8 hp help

i agree, gunged up jet in high speed circuit is likely cause and not restricted air flow

BTW- it is a 2010ish 4 stroke, pretty sure MFS8A3EFL.

Any easy fixes- sprays, additives, what have you, worth trying?

If not, would I need to disassemble the carb completely, or might I be able to access the jet, and clean it with a wire?

BTW- thanks. for the quick responses. A frustrating season:

? Season 1- Bought boat with Yamaha. Ran a little rough.
? Season 2- Brought motor to shop, carb clean, ran great.
? Boat sat for a couple weeks, would not start at all.
? Brought carb to second shop. They cleaned the carb. Re-installed carb on last day of season to pull boat. Started and ran beautifully, but spit gas out of the bottom.
? Left carb at shop on my way home for the season. They replaced the accelerator pump diaphragm, which was leaking.
? Season 3- picked up carb, re-installed. Motor started and ran beautifully, but spit gas out the bottom of carb.
? Shop is reputable, but 1.5 hrs from house. 2 round trips = 6 hours driving time. Opted to have fixed locally.
? Re-installed carb. Motor ran perfect. Tested in a barrel, ran well at all speeds. Repeatedly.
? Went to launch boat, blew a brake line in truck.. Very lucky I did not launch the truck. Or crash on the highway.
? Returned a few days later when marina said they could launch me, as my truck is not fixed. Marina was too busy to launch me.
? Returned a few days later to sail. Motor does not work at all.
? Took Tohatsu, which had been fogged and stored properly, then tested multiple times at home. Transported it properly to marina, and enlisted their help to swap, as boat is on a mooring, and I have no truck yet. Tohatsu runs as described in my first post.

 

[JB]

Re: Tohatsu 8 hp help

A correct overhaul of the carb does require complete dismantling. Give particular attention to the orifices that pass fuel into the airstream in the bottom of the throat.

 

[pvanv]

Re: Tohatsu 8 hp help

1. There isn't any air filter.
2. Sounds like you have fairly severe varnishing in the carb passages.
3. Verify that you are about 1/2 to 3/4 on the oil dipstick. Not a drop over full.

You will want to remove the carb, completely disassemble it -- including jets and emulsion tube nozzle, and soak it for 4 hours in real carb dip, followed by a liberal spray-out of all passages with generic carb spray. Then do a careful reassembly, paying attention to float height. Never ever use any sharp wires, etc to attempt to clear varnishing. Failing that, you may need a new carb.

You can also install the 9.8 carb to increase your power.

In the future, always, religiously, run the carb out at the end of each and every day (by disconnecting the fuel hose quick-connector at the motor.)