Thread: 1974 Tohatsu B18D outboards

Hi Fella's

Have bought 2 complete and one bitser Tohatsu outboards. A mate and I have managed to get one of them running and are going to try and get the other complete one running too.

So far the main issue we have is that there is no "tell tale" water spurting visible straight away like my mates 1990's mariner 40hp.

Am waiting for a seller on ebay to allow international shipping on the auction for a service manual.

Was hoping someone on here could let me know the following.

Is there a thermostat? a google search says that there isn't one.

Is there a "tell tale" a youtube search says yes but i can only go off the fact that the videos are of old tohatsu's that look pretty similar.

Where does the water pump out of? on the youtube videos it appears that it comes underneath where the power head is and out of 3 holes on the middle driveshaft housing.

any other information would be great. Also feel free to flame me for buying something so ancient.

Cheers

Water pump impellor or holes blocked usually

Disassemble the water pump. At that age the rubber impeller (if not serviced) may well have decided to return to its origins and have become bits of rubber.

Three main causes - rooted pump or pump not operating efficiently (this could be due to the impellor worn/failed or mechanical issue with the pump componentry or intake or plumbing), blockage in the engine casing or with the temp regulation circuit (there should be a thermostat in there somewhere to prevent the engine from running cold and these often corrode shut if not flushed correctly then left for a period of time) or the telltale weep hole is blocked.

It would pay to not use it until you work out whats going on as the waste cooling water is dumped out the exhaust to cool that, which means that if there is insufficient water flow it's not doing the required cooling.

Cheers fellas. I'll try and get the service manual asap and hopefully disassemble it so I can get a generic part locally or online.

Some early outboards did not have tell tales. Years ago I had a 63 18hp johnson seahorse and it had no tell, pretty sure even into the 70's some Johny's had no tell. you had to look for water coming out the leg through the exhaust port about 2/3 down the leg. If it has a tell you'd think it would be visible somewhere on the castings. If it blew water out of the exhaust and didn't appear to get visibly hot running in a bucket getting smelly/steamy etc it might be ok. Those cheap point and shoot infrared thermometer guns are handy for checking external engine temps.

As has been said: I'd inspect the impeller first, that will probably give you some clues to what's going on

And yes you must have got them for nothing to make the effort worth while. How available are parts? Do they have points? if so I would turn them into scrap metal.

Originally Posted by Got-ya

And yes you must have got them for nothing to make the effort worth while. How available are parts? Do they have points? if so I would turn them into scrap metal.

I got two running motors (a short and a long shaft) and a parts motor for 470 bucks. So far I have found gaskets, carburetor rebuild kits etc. When I get the manual I should be able to confirm the part numbers.

At this stage the dinghy it will power will never be worth more than 300 bucks so there's no point in putting a 1000 dollar outboard on it when if I eventually upgrade it would be to a larger boat than a 10hp could propel. If they can be made to run cheaply then they're worth saving imo. For an 8hp they're man portable.

I don't know what points are. it has ignition leads, spark plugs and two plastic things that work.

8hp or 18hp ??? they did make an 18 later on...they went VERY well indeed,similar size and weight to most 15hp motors...

Originally Posted by yerimaginaryM8

Some early outboards did not have tell tales. Years ago I had a 63 18hp johnson seahorse and it had no tell, pretty sure even into the 70's some Johny's had no tell. you had to look for water coming out the leg through the exhaust port about 2/3 down the leg. If it has a tell you'd think it would be visible somewhere on the castings. If it blew water out of the exhaust and didn't appear to get visibly hot running in a bucket getting smelly/steamy etc it might be ok. Those cheap point and shoot infrared thermometer guns are handy for checking external engine temps.

Correct. My 1976 85hp Johnson outboard sent me spare trying to figure out where the tell tale should be coming out. In the end I twigged, and looked it up on line. So just carried one of those cheap thermometer guns as insurance if things began smelling warm.