Tohatsu MFS 25 won't choke

[emarshbuck]

I had to reconnect some wires out of my switch to a harness connector due to some broken/bad wiring. Everything works except the choke (motor cranks, PTT, power to the bus bar, lights, etc). I have 11 wires coming out of the main engine harness to my switch:

red
black
blue
light blue
pink
yellow
brown
green
lime green
white
red w/yellow

Any idea which of these wires controls the choke and needs to either get power fed to it or be grounded? Engine is a 2004 MFS25A. I have the wiring diagrams for these engines, but even my neighbor who had boats for 30 years can figure out which wire controls the choke.

thanks,

ed

 

[pvanv]

Blue. 12v causes the choke to close.

 

[emarshbuck]

Paul, so I need to feed power to it?

Hope Phillipe misses you....

thx

ed

 

[emarshbuck]

Paul, the blue wire that comes from the engine (along with the other wires) is feeding into my switch. The switch has power to it. When I turn the switch to on, and press in the key so as to activate the choke, nothing happens. Is there a way to test the choke? Could it be a bad switch? The switch has 6 wires coming out of it, brown, black, blue, green, and two reds. the blue wire is going in to the wiring harness back to the engine.

thanks,

ed
Hilton Head, SC

 

[pvanv]

Like any wiring test, check at the 1/2 way point, and you will know which side the trouble is on. If pressing the key delivers 12v to the solenoid, the solenoid or wire to it is bad. If not, you may have a bad key switch, or the power going to the switch may not be active. Likewise, if you put 12v on the blue wire, the choke should activate.

 

[emarshbuck]

Paul,

I exposed a bit of the blue wire and jumpered a wire from the positive battery post to the wire....should I hear the choke activating? Do I need to push in on the switch while jumping power to the blue wire? The key switch has power to it and the engine will crank, just not start and my two veteran boating neighbors suspect the choke....

thx
ed

 

[pvanv]

You should both see and hear the choke close when 12v goes to the solenoid. If not, you may need a new solenoid. Does the blue wire have 12v when you push the key? A lot of things could keep you from starting, so you may want to investigate further.

 

[emarshbuck]

YES! I just checked and it does have 12v when key is pushed in....so, that means the key switch is ok, yes? I have the parts catalog for the motor, and it says that only the EP & EF model motors have a starter solenoid. My engine is an MFS. I looked at the engine and could find nothing near the starter motor that looks anything like the parts diagram for a solenoid. I did see that the blue wire coming out of the harness goes into a wiring connector, and the same wire does not come out the other side, so I'm guessing something "magical" happens inside that connector.....7 wires go into the connector (BL GR LtGR Y BLack Br W) 6 wires come out (GR LtGR Black BR Y W). The back end harness is Cord Assembly A, pn 3R0-76110-0. How to test the choke from here?

thx again....why did I succumb to wife's desire for a boat? Although it is nice to motor around the creeks and intercoastal here watching dolphins, manatees, and real boats...:>)

ed

 

[emarshbuck]

Paul,

Breaking news ( I think). Tested voltage all the way back to the choke. It's got 12v. Took the choke out, jumpered power/ground to it, nothing moved. Tested continuity, has continuity (meter made the whistling sound.) Then, just for the heck of it, I put my thumb over the venturi hole, neighbor cranked the engine, after a couple of tries, engine started!

I'm calling my Tohatsu dealer tomorrow and giving him the same info.....

thoughts?

​ed

 

[pvanv]

The MFS25A could come in EF (tiller/electric) or EP (tiller/remote).
The 25A uses an auto-by-starter solenoid, which has nothing to do with "choke".
Odds are you need to clean all 3 carbs. The passage in the bowl that feeds the ABS is probably clogged.

 

[emarshbuck]

Paul, confirmed with my local Tohatsu shop that I have the EP type. Porcelain auto-by-start. I removed it to test it, didn't seem to make any movement when I jumpered it. I was able to get the engine running for just a second by spraining carb starter. But it would not continue to run even as I pumped the control box and could see the carb valve pins working. Tohatsu shop thinks I need to clean the carb. It is true that we did not use the boat much this year, and I didn't have any Sta-bil in the gas tank. Can anyone point me to a video or link as to how to take this carb off and clean it? My next door neighbor had boats for 30 years up on lake Michigan, and he's very mechanical about these things. I am to some extent but never cleaned a boat carb.

thx

ed

 

[pvanv]

That motor has three carburetors. The top one has the ABS solenoid. You test the solenoid by applying 12v for several minutes; it should heat and the pin should extend over time (as the motor is warming up).

Each carb must be completely disassembled (including jets and emulsion tube nozzles, and then all non-rubber parts submerged in carb dip (available at auto parts houses) for at least 4 hours. Then a liberal spray-out of all passages with generic carb spray. Really blast it with the little red straw. Count on maybe 2 aerosol cans for the 3 carbs. Pay special attention to the passage in the bowl that feeds the accelerator pump and ABS cavity. There is a very tiny screw (I think it's a phillips size zero) that allows the accelerator pump to come apart; be careful with that, and don't lose the return spring. If you don't disturb the mixture and idle stop settings, you will probably not need to re-synchronize the carbs when reinstalling. You may or may not need three new carb kits (available from any dealer) when reassembling. You may need new base gaskets. If the bowl is corroded (with white residue that won't clean off), it is available separately.

When reassembling each carb, pay careful attention to float height. If it's off, install a new needle and float. It will be tricky getting the accelerator pump linkage and boot apart, but the carb dip may well damage the boot, so you do want to take that apart. New boots come in the carb kits, or are available separately. I always have a couple on hand in the shop.

In the future, try to only run non-ethanol fuel, 30 or fewer days old, and always, religiously, run the carbs dry at the end of the day, or drain them with the drain screws. Stabilizer helps prevent rotting of the fuel, but does not stop evaporation, and the resultant varnishing. In any event, it is wise to open the drains when storing for the off season, as the accelerator pump passage may still have fuel in it, even after you idle the fuel out of the carb.

 

[emarshbuck]

Yeah, I figured out the ABS thing talking to the Tohatsu dealer down here....I took it out, jumpered it directly to the battery, and the needle didn't seem to retract at all, though I didn't leave it on for more than a few seconds. I sprayed some carb starter fluid into the ABS hole, stuck the ABS back in, and the motor started, just for a second. Tohatsu guy recommended trying to blow some compressed air through that upper carb to maybe clear out the passage. Meanwhile, I'm searching for a reasonable price mechanic to clean all 3 carbs. I'm thinking it's not something a novice like myself (even with my neighbor's help) would want to undertake.....what do you think would be a fair price for this, parts & labor? thx

 

[pvanv]

The ABS extends as it heats; it doesn't retract. It takes a few minutes. Carb work is all time and materials. If you buy 3 carb kits ($58 per kit MSRP), then figure at least 1 or 2 labor hours. Could be more depending on how bad the passages are. We get $90 an hour, but may go to $100 next year.

 

[emarshbuck]

Paul,

I jumpered the ABS to my battery for 5 minutes....sure enough, just as you said, it extended 2cm. Went from 8-10cm from the base of the ABS. Let it cool down, put the ABS back in, motor won't start. Take it out, put my thumb over the opening, starts right up. It runs rough, and when I remove my thumb, it chokes out.

Now, when we start it with the thumb over the opening, take my thumb off and insert ABS, it keeps running, although rough. When I raise the ABS maybe 1cm, it runs smooth. I see two tiny openings where the chrome part of the ABS sits. Is the chrome part sitting too low in that chamber? My two "boat pros" recommend replacing the ABS.

thoughts?

thx

ed

 

[pvanv]

The ABS is fine. The passage in the bottom of the carb bowl is gunked up.

 

[emarshbuck]

any way to clean out that bowl w/o a total 3 carb cleaning? parts/labor here is $450.....

 

[pvanv]

Pull the carbs as a unit. Separate the top carb. Disassemble it and clean the bowl. If too bad, I can sell you a new bowl.

3R0032210M

FLOAT CHAMBER, UPPER

$53.97

 

[CamaroMan]

Hi - been

I had to reconnect some wires out of my switch to a harness connector due to some broken/bad wiring. Everything works except the choke (motor cranks, PTT, power to the bus bar, lights, etc). I have 11 wires coming out of the main engine harness to my switch:

red
black
blue
light blue
pink
yellow
brown
green
lime green
white
red w/yellow

Any idea which of these wires controls the choke and needs to either get power fed to it or be grounded? Engine is a 2004 MFS25A. I have the wiring diagrams for these engines, but even my neighbor who had boats for 30 years can figure out which wire controls the choke.

thanks,

ed

Hi, im struggling to find the pin out diagram for the nissan 25a im working on - nothing online that i can find, do u perhaps have anything to share? trying to get it to crank on a stand for testing and dont have the plug.

 

[pvanv]

Full info is of course in the Factory service manual. Where is the plug?