Tohatsu M18C2 information.

MTboatguy

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Just thought I would let everybody know, if you are rebuilding the fuel pump on this motor and also need carb parts, I found a place that has virtually everything for these carbs. also, be very careful, if you are putting the fuel pump back on while the carb is still on the motor, you have to hold 5 gaskets, 4 screws and monkey around getting the fuel line hooked back up to the bottom of the fuel pump, not easy for a guy with fat fingers to do. I finally ended up putting a piece of blue painters tape across the screw heads and taped to the side of the fuel pump body, this held the screws in all the way, and you hang the gaskets in the right order on the screws, then carefully match up to the screw holes in the carb, peel the tape back carefully on one screw head at a time and get it started in the carb, then pull the tape completely off and firm them up. Took me a little while to figure that one out!
 

Sea Rider

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What a huge difference between C2 and D2 carb pumps. On latter just 3, front gasket, middle diaphragm and rear cover gasket. Better is to change those with carb removed from intake as there's limited hand space to work properly.

Happy Boating
 

MTboatguy

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What is odd on these fuel pumps is in looking at the original service manual, it shows the outer cover, then Pump cushion diaphragm, fiber pump cover gasket, then pump body, fuel pump diaphragm, then two pump body gaskets. In some of the other diagrams I have seen is shows the fuel pump diaphragm between the 2 pump body gaskets. So I guess, I will have to try it and see which way it works, right now, I have it as the factory service manual shows.

This diagram at maxrules, shows the fuel pump diaphragm between the pump body gaskets.

http://www.maxrules.com/graphics/TOA/mtm_C8_kit_parts.jpg
 
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Sea Rider

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The C2 carb model is quite different than the new D2 carb, that's why the huge internal parts difference. Now much simplier.

D2 square housing operates with 2 internal reed valves, does C2 same ? If so remove both housing side gaskets should work fine.

Happy Boating
 
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MTboatguy

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Yes, the C2 has the check valves in it. I put it all together today, got the filter housing working correctly, fire it up and it ran for about 1 minute, sounded good, then quit and would not start again. So I pulled the carb off it and will open it up in the AM to check and clean everything, this one has me really scratching my head, it ran great a couple of weeks ago, then nothing, nada, won't keep running, new plugs, good fire. Etc. so hopefully I will be able to get things cleaned up and get it fired again, I am about ready to give up on the tohatsu.

Another thing, it ran for about a minute and the amount of black in the test tank was amazing, I poured it out and have a large black stain on the grass, my wife is ready to shoot me!
 

Sea Rider

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MT,

Sorry to read you're having huge issues with that nice and docile horse. If complete fuel system, tank, hose, fuel pump carb are in good working order probably is not a fuel related issue, could be an electrical one, a component overheats and engine drops dead untill cools down and starts up again in on/off cycles. Other culprits that matches those symptons are head gasket is shot or worn fuel connector small o'rings.

Happy Boating
 

MTboatguy

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Well I did tear it apart and cleaned it up, it was pretty dirty inside, the bottom of the bowl was covered with a copper colored dust, enough so, that the drain screw at the bottom of the bowl was not clear. The float needle is still in great shape, but I had to use a pair of tweezers to pull it out of the jet, so I cleaned all of that up, there was gunk in the jet that was sticky, used a small copper wire(Bread Bag Tie) to make sure the passages were clear and cleaned up. I will be putting brand new fuel line together tomorrow, and try to fire again and hope it runs. Unfortunately, I was not able to find a new engine side fuel fitting, but in checking it the o-rings seem fine. Compression is great on this motor, I already checked that. So if things don't work out in the AM, it can only be one thing, electrical.
 

Sea Rider

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If having all described carb issues you should run bowl dry after each outing specially if engine will not work for long time periods. You'll be amazed on problems that worn fuel connector o'rings can provide. When old o'rings become hardened over time and use, won't seal well against fuel male connectors, air will enter through line, carb and engine will start missing, worse when giving juice. The slight or worse miss will depend entirely on how worn those small o'rings are, a new fuel line cures the sick but can be costly.

If wanting a cheap cure remove both o'rings with a thin needle, go to a car shop and buy same diam new, replace and voil?. It's an out of this world crime that those small o'ring which gives issues doesn't come as spares. Tohatsu nonsense as some other pearls found on the existing 18.

Happy Boating
 
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MTboatguy

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I have lots of O-rings, I have 180 piece viton kit that I bought so I could repair my snowplow when needed and I have a 400 piece nitril kit of just regular O-rings for other various things I need to do through out the year, when you live as far as I do from the parts stores, you learn quick to keep stuff around to fix anything that might pop up.
 

MTboatguy

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Well Crap, still no run, it is not even trying to fire, even when I squirt a bit of starting fluid into the carb, I am at a loss!!!!!!!!!!!!!!!!!!!!!!!
 

MTboatguy

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I did on Thursday afternoon when I was messing around with it and when I use the pull rope to try and start it, there is good resistance. With the amount of black residue in the water, I am starting to wonder if it might have a burnt piston, I didn't even get it started yesterday and the lower unit is covered with black residue and the top of the water was totally covered with black oily residue, just does not seem normal to me.
 

Sea Rider

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You need a whole can of CRC carbon remover, remember the air silencer modification, go for it. After the procedure go for a wot spin for at least 2 minutes as if were stealing the combo to get all those unburned oil deposits out powerhead and specially exhaust area.

It's no good to test engines on a barrel for long time periods, you'll accumulate excessive unburned oil residues on lower leg including sorrounding water. Better is on a engine stand with muffs. You are probably mixing too much 2 stroke oil than 50:1 ratio. Only need 80 Mil per 3.80 Ltr gallon.

Happy Boating
 
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MTboatguy

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I don't think I am mixing heavy, but I might, but I have put it to bed now and will pull it back out in a few weeks, I have two weeks and we are going to Yellowstone for a week and I have a few things to do on the 5th wheel, I will sit down there and scratch my head for a while, but again, I am really stumped with this one.

Thanks for your help Sea Rider.
 
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