Logo
FULL SITE MENU

Tohatsu Carb leak

S

snookwhaler

Regular Contributor
2002 25hp Tohatsu 4 stroke. Runs beautifully, no issues in that department. BUT, I have a fuel leak on the lower carb. The engine has 3 carbs and the lower carb is leaking lots of gas out of what looks like an "accelerator pump".

Facing the carbs, there is a linkage that connects all three carbs together. On the back of the carb (on all 3 carbs) there is a rod that comes through a brass bushing. This rod is connected to the linkage on every carb. On the other 2 carbs there is a rubber boot that surrounds this rod. On the lower carb, the boot is gone or deteriorated.

Is the "boot" keeping the gas from leaking out? Or is there a problem, o-ring, etc.... inside the carb that has gone bad. I can get a pic if needed.

Any help appreciated. I can pull them off if needed. Trying to avoid that though.

Again.... This engine runs perfect otherwise.
 
Last edited:
First, your motor is an MFS25A. Year is unimportant. Yes, the carbs have plunger type accelerator pumps. Yes, all should have boots. The boots are not fuel seals. That carb is probably flooding. In any event, you need to pull the carbs if you want to change the boots. If they have not been cleaned in over a dozen years, it's probably time to pull them, clean them properly, and install new kits. The boot is:
3R3033111MRUBBER BOOT$5.67

 
pvanv said:
First, your motor is an MFS25A. Year is unimportant. Yes, the carbs have plunger type accelerator pumps. Yes, all should have boots. The boots are not fuel seals. That carb is probably flooding. In any event, you need to pull the carbs if you want to change the boots. If they have not been cleaned in over a dozen years, it's probably time to pull them, clean them properly, and install new kits. The boot is:
3R3033111MRUBBER BOOT$5.67
Click to expand...

Thanks! I really appreciate the input. Yep, that's the number on the side of the lower cowl. This boat/engine is new to me, engine is low hours and the guy I bought it from said carbs had just been gone through (this made me a little nervous). The engine ran a little rough when I got it. So, I pulled out my gauges and balanced and adjusted idle mixture on all 3. Purrs like a kitten now.

So, today I go out to remove the carbs and find a tiny washer down in the bottom of the cowl. As I was removing the drain screws for the float bowls (to drain the gas out), I found that one of the brass screws was missing a washer. Now I am thinking that this guy tried to do the carbs himself and god knows what else he screwed up now that I am finding stuff like this! I also found one of the bushings for the intake horn missing and a seal between one of the carbs and intake is missing!

So frustrated now. I'm gonna take a day or 2 off. I'll post back what I find on the bottom carb. Thanks again for the help.

I no newbie to carbs, but is there anything I should be looking for in there besides a stuck float or fuel saturated float? Also, is there an o-ring in that brass bushing?
 
Sounds like you are on the right track. Pull the carbs and see what is missing/damaged, and replace as needed. The floats are hollow plastic and very very rarely get full of gas, so the more likely problem is a bad needle tip, or a sticky float. AFAIK, no o-ring in the plunger link bushing.
 
OK.... I got them apart today. Not too horribly dirty (I've seen worse). There was definitely some kind of fuel stabilizer in there. No o-ring in that bushing the accelerator pump rod goes through. It is actually pretty loose in that bore. The only thing that keeps "atmosphere" out of the float bowl is that boot mentioned above. Getting that little rod out of the bore was like a puzzle. Took me a minute to figure it out. Just waiting on parts. Not looking forward to "syncing" them again. Kind of a PITA compared to other engines I have worked on. Other than the Aforementioned washer and bushing missing, everything else seems to be intact. Thanks again!
 
Last edited:
if that washer was missing from the drain plug on the lower carb, that might be your leak. What is the trick to removing that link rod, I need to replace the boot.
 
Back
Top