2003 Tohatsu 18Hp four stroke MFS1882

[rcb130]

I forgot to ask: Is there a pressure and vacuum test for the fuel pump? If so, what are the specs?

 

[rcb130]

what should I expect on DVA? I am reading 94 while running then as the motor starts to stumble it begins dropping off.

 

[pvanv]

Paul,
I did not mean to allude that changing the coil affected the ABS. It just happened that I tested ABS voltage after changing the coil.I test the rectifier with a digital "true rms"multimeter and get flakey readings. I test with an analog and it tests ok. When I have the motor running and probe the yellow leads at the ABS I do not get 12 volts DC, but millivolts. Applying 12 volts to the ABS does cause the needle to slowly extend. Motor appears to be charging battery.

Because the ABS loads the circuit, you will likely not see 12v while running, if the ABS is connected. If you unplug it to test, you should see 12v with a good analog meter. Of course, as the ABS cools during the test, the idle section of the carb will richen, so be brief when testing.

 

[pvanv]

I forgot to ask: Is there a pressure and vacuum test for the fuel pump? If so, what are the specs?

Fuel pressure should be at least 1 psi; vacuum should be adequate to lift fuel 3 feet from a tank.

 

[pvanv]

what should I expect on DVA? I am reading 94 while running then as the motor starts to stumble it begins dropping off.

94 DVA going into the ignition coil is good. The dropoff could be either because the motor is slowing down, or because a part is failing -- causing the slow-down. Since you have tried a different coil with the same results, if there is failing ignition, look at the exciter, trigger, and CD when they are hot.

 

[rcb130]

I may have found the problem. As you originally thought it appears to be fuel delivery problem. I disconnected the fuel line feeding the carb and cranked the motor. strong spurts of fuel. I tried blowing into the fuel line to the carb after removing the carb bowl drain screw and only a small amount of fuel drained out. I could not blow thru the carb into the fuel bowl. Removed carb again and blew a half can of carb cleaner thru the needle valve seat. The engine will now run without stalling out. Is the needle valve seat removable for cleaning or replacement? If so, how do I get it out? I do not see a replacement listed for the seat.

 

[pvanv]

The seat is pressed integral with the casting, but you can get just the needle.

3R3032390M

FLOAT VALVE

$10.72

Typically either the rubber tip got sticky, or some oxidation of the aluminum of the needle causes it to not slide freely.

 

[rcb130]

when I check the alternator coil do I check the yellow and white at the rectifier or at the cd connector?

 

[pvanv]

when I check the alternator coil do I check the yellow and white at the rectifier or at the cd connector?

Yellow and white is the tach hookup location. If testing for charging, I would check the feed to the rectifier, and run the ohm tests on the rectifier. If testing the power to the ABS, remember that one of the yellow ABS wires is actually connected to a black ground wire; the other one comes from the CD module. See the wiring diagram in your owner's manual.

 

[rcb130]

If I check the alternator coil resistance which I think I am doing at the cd module connector between the yellow and white wires I get an "open" condition. Are these not the wires from the alternator coil?

 

[pvanv]

The alternator has several coils. Of the white/yellow tach pair, white is ground. What service manual are you using?

 

[rcb130]

Tohatsu outboard service manual 4 stroke cycle 9.9-15 PN003-21041-0. Page 122 gives resistance for alternator coil between Yel and Wht as 0.21-0.41.

 

[pvanv]

Yes, that's the correct value for the yel/wht pair going into the rectifier/regulator.
You must use a good-quality ANALOG ohmmeter.
The wh/yel from the CD feed the tach, with white as signal ground.

 

[rcb130]

I pulled the carb again and removed the float valve needle. I took some 1200 grit paper to the shoulders on four sides of the needle, sprayed it real good with carb cleaner and put the rest of the can of carb cleaner thru the needle valve seat. Reassembled carb, replaced plugs as I believe they were the originals. Gave one shot with the fast idle lever, hit the key and it was running. I believe the needle valve was sticking as the motor would run for about 3-4 minutes and start to stumble but would pick up the rpms as the float valve opened. It no longer does that. Waiting for the owner to listen to it and see if he is happy. Paul,Thanks for all the help and advice you gave. It is greatly appreciated.