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Flooding issues with Tohatsu 8 HP 2-stroke

Apr 11, 2020
151
Hunter 170 Grapevine
I have enjoyed using an older Tohatsu 2-cycle 8-horse outboard motor on my Mac 26S that is, until recently.

For most of this season (starting in March here in North Texas) the motor has started right up, never needing any choke even when "cold". Lately, I have had trouble starting it and found I had to run the starter for quite a while before it would finally catch. Once started, I had to carefully apply throttle to keep from killing it until finally I was able run the excess gas out. Lots of white smoke in the process, so quite obviously flooded.

This morning it would not start at all. I tried disconnecting the fuel line and cranking and cranking, but to no avail. I made several attempts over the course of the next 20 minutes or so. Finally I gave up and we just had our picnic lunch at the marina and went home to put the grandkids down for a nap.

When I came to take the motor off the boat (maybe 2 hours later), I decided to give it another try and it started after a fair amount of cranking, again with careful application of throttle and a big cloud of white smoke. After that it ran fine and would start back up easily. Something I did notice was that if I pumped up the pressure with the fuel line priming bulb that fuel would drip from the bottom of the fuel pump, but it's hard to say if it was leaking from the fuel pump body or from where the fuel line attaches to it.

A friendly expert at the marina suggested that in the future I just unhook the fuel line from the gas tank and let the engine run dry after use. He opined that the ethanol in regular gas wreaks havoc on the fuel line and other components when allowed to sit. I think that stands to reason, so that will be my practice going forward. I intend to replace the fuel lines, fuel pumps gaskets, and fuel pump diaphragms for good measure.

I would welcome opinions and feedback on this, as I missed really nice day for sailing toward the end of the season and wish to avoid a repeat of the experience.

Thanks!
 
Feb 10, 2004
3,508
Hunter 40.5 Warwick, RI
From your description and my experience it sounds like the float valve in the carb is not sealing and it is allowing too much fuel in the bowl. Or the float has absorbed fuel and it is letting in too much fuel. Either way a rebuild kit should fix that issue.
The fuel drip sounds like a different issue and one that could be solved by observation.
 
Jan 11, 2014
7,822
Sabre 362 113 Fair Haven, NY
White "smoke" is likely water vapor. On a 2 stroke the smoke should be blue.

One of the issues with ethanol is getting water in the fuel. It may be that you do have water in the tank which causes the white smoke which is really steam.

Older motors were not designed or built to deal with ethanol in fuel. It is best to use ethanol free fuel for older outboards and many smaller 4 cycle motors (such as lawn mowers, chain saws, outboards, etc.). @thinwater is the expert on this, perhaps he'll chime in.
 
Apr 11, 2020
151
Hunter 170 Grapevine
White "smoke" is likely water vapor. On a 2 stroke the smoke should be blue.

One of the issues with ethanol is getting water in the fuel. It may be that you do have water in the tank which causes the white smoke which is really steam.

Older motors were not designed or built to deal with ethanol in fuel. It is best to use ethanol free fuel for older outboards and many smaller 4 cycle motors (such as lawn mowers, chain saws, outboards, etc.). @thinwater is the expert on this, perhaps he'll chime in.
My "expert" mentioned the use of Trufuel, and that several people he knows use it, the added expense notwithstanding. As little fuel as this motor uses, perhaps that is an option I should pursue.
 
Apr 11, 2020
151
Hunter 170 Grapevine
Thanks for that. Apparently, Grapevine Texas is an E0 desert.
From your description and my experience it sounds like the float valve in the carb is not sealing and it is allowing too much fuel in the bowl. Or the float has absorbed fuel and it is letting in too much fuel. Either way a rebuild kit should fix that issue.
Thanks. Is there a way to tell if this is the problem (or part of it)?
 
Jan 11, 2014
7,822
Sabre 362 113 Fair Haven, NY
I just came back from rescuing a dinghy. A neighboring sailor was trying to get back to his boat that was upwind in 10+ knots. His normally reliable motor kept stalling out. The problem it seems was the vent on his gas tank (internal tank), he had left it open the day before in the rain and water had entered the tank.

If you are using an older tank that vents, water may have entered from rain, spray, or condensation. That coupled with the E10 could cause the problems you're experiencing.
 
Feb 10, 2004
3,508
Hunter 40.5 Warwick, RI
Is there a way to tell if this is the problem (or part of it)?
I have seen flooded carb bowls drip out of the air intake, but you said it was dripping from the fuel pump. Doesn't sound the same to me. But I am not familiar with your engine.
 
Apr 11, 2020
151
Hunter 170 Grapevine
I just came back from rescuing a dinghy. A neighboring sailor was trying to get back to his boat that was upwind in 10+ knots. His normally reliable motor kept stalling out. The problem it seems was the vent on his gas tank (internal tank), he had left it open the day before in the rain and water had entered the tank.

If you are using an older tank that vents, water may have entered from rain, spray, or condensation. That coupled with the E10 could cause the problems you're experiencing.
Thanks for that input, but my gas tank is protected from the elements in the lazarette.
 
Apr 11, 2020
151
Hunter 170 Grapevine
Update:
After disconnecting the fuel line and running the motor dry on Saturday, today I connected the fuel line, gave the bulb a few pumps and the motor started up, no trouble. I am beginning to think the problem lies at least to some extent with the fuel tank creating pressure that causes the carb to flood. After sailing for a few hours, it did take a several tries to get it started again - acting like it was a bit flooded. This was not a problem in the past, so something has happened over the course of the summer aside from just pressure in the fuel tank, I think. My plan is still to replace fuel lines and fuel pump diaphragms (winter project), but in the meantime I think I will install a petcock in the fuel line just upstream of the coupling at the engine. That way I can just shut it off rather than having to disconnect the fuel line.

Someone at the MacGregor forum just shared this with me. Interesting...
 
Jan 11, 2014
7,822
Sabre 362 113 Fair Haven, NY
The tank for my dinghy OB is a sealed tank with the pressure valve. The sealed tanks will develop a lot of pressure due to sitting in the sun or just temperature differences.

Adding a valve to your hose might be the best solution or just replace the hose with a new one that has the valve. Do you have a ventless tank?
 
Apr 11, 2020
151
Hunter 170 Grapevine
Well, the tank has a "vent" knob on the cap, but it is useless. The only way to relieve pressure in the tank is to loosen the cap.

I think it is ironic when you realize that the purpose for these non-venting tanks is to reduce the amount of hydrocarbons released into the atmosphere, but the system is such that it requires the replacement of pretty much everything between the gas tank and the motor with the addition of a valve that is made from plastic. Wonder what the total carbon footprint of that is in comparison to the fumes from the old systems.
 
Jan 11, 2014
7,822
Sabre 362 113 Fair Haven, NY
S
Well, the tank has a "vent" knob on the cap, but it is useless. The only way to relieve pressure in the tank is to loosen the cap.
This may be the issue. Have you noticed correlation at between time of day or temperature? As the day cheats up the pressure may increase forcing more fuel into the carb causing the flooding.
 
Apr 11, 2020
151
Hunter 170 Grapevine
Well, I had the boat out this evening and noticed that smoke exiting the engine cover. It abated after a few minutes. I am convinced that fuel is leaking inside the engine cover. My suspicion is that fuel lines and perhaps portions of the fuel pump have been damaged by the ethanol fuel and pressure from the "improved" fuel tank. I have ordered a petcock so I don't have to disconnect the motor from the fuel line, but may end up throwing down for a fuel demand valve to avoid having to release pressure from the gas tank every time I use the boat. I still intend to replace fuel lines and fuel pump diaphragms.
 
May 24, 2004
6,788
CC 30 South Florida
Check prices of rebuild kits vs. a new carburetor, sometimes the kits don't do it and the price differential may not be worth the cleaning hassle and continued operating problems.
 
Apr 11, 2020
151
Hunter 170 Grapevine
Check prices of rebuild kits vs. a new carburetor, sometimes the kits don't do it and the price differential may not be worth the cleaning hassle and continued operating problems.
Thanks for that. I will definitely explore new carb prices if my "easy" fixes don't cut it. I'm definitely not into spending a whole day to save $100, then hoping I did it right!
 
Apr 8, 2010
1,620
Ericson Yachts Olson 34 28400 Portland OR
Maybe not part of the current problem, but you might want to replace the hose from your tank to the engine. A good friend of mine started having starting problems and running problems with his mid-70's Honda. This was back in the 90's.

After a bit of trouble shooting it turned out that the original fuel tank hose was starting to shed rubber bits from the liner layer and this was clogging up the carb.
New hose and squeeze bulb totally fixed the problem (he may have rebuilt the carb, but I do not remember that detail now.).
 
Apr 11, 2020
151
Hunter 170 Grapevine
Interesting! Yes, my bulb and hose are old. I bought a new hose and bulb from Academy (Marine Raider brand) and it was a POS, had to practically stand on the bulb to get it to pump, so I just keep using the old one. I regularly check the fuel filter, and am seeing nothing there, but it's good to know other's experiences.
 
Mar 26, 2011
2,935
Corsair F-24 MK I Deale, MD
Normally you do not need to rebuild the carb, only clean the needle valve seat with carb cleaner. Just pull the carb and do it. Skip the kit. 15 minutes.

No-vented portable gas tanks require a demand valve in the supply line. Kind of a back-up to the carb valve. Any boat store has them, no problem.

Do ...
  • Keep the vent closed when not actively running. This keeps the water out of the e-10.
  • Use an effective anti-corrosion additive. It is often aluminum corrosion gel from the aluminum carb that causes the plugging and valve leaks. Biobor EB, Stabil 360, and Merc Stro-N-Start have tested well. Most are snake oil.
  • Run the engine frequently. I start every gas motor I own, including seasonal lawn equipment, every few months. Makes all the difference.
E10 is not all that bad, you just have to follow the rules. E10 rules. (My career was refinery engineering)
 
Apr 11, 2020
151
Hunter 170 Grapevine
Normally you do not need to rebuild the carb, only clean the needle valve seat with carb cleaner. Just pull the carb and do it. Skip the kit. 15 minutes.

No-vented portable gas tanks require a demand valve in the supply line. Kind of a back-up to the carb valve. Any boat store has them, no problem.

Do ...
  • Keep the vent closed when not actively running. This keeps the water out of the e-10.
  • Use an effective anti-corrosion additive. It is often aluminum corrosion gel from the aluminum carb that causes the plugging and valve leaks. Biobor EB, Stabil 360, and Merc Stro-N-Start have tested well. Most are snake oil.
  • Run the engine frequently. I start every gas motor I own, including seasonal lawn equipment, every few months. Makes all the difference.
E10 is not all that bad, you just have to follow the rules. E10 rules. (My career was refinery engineering)
Well, there's an authoritative source if ever there was one!

Vent closed when running. Check. Recent fuel leak into the lazarette has me schooled on that one.
Run the engine frequently. Check. The guys at the marina say I am out there more than the ducks.

I have a few gas additives on my garage shelf. Would either of these serve as an anti-corrosive?
-Mercury Quickare
-Sea Foam

Thanks!