Friday, January 5, 2018

Tohatsu 6hp Outboard 125 Hour Service

The specified service frequency is actually 100 hours, but I'm not perfect, right? I installed the outboard in December 2014, so that is 3 years to accumulate 125 hours, or around 42 hours per year. On the other hand, the last three years have been low mileage as I have been fixing a house at the same time, so that makes those hours on the low-use side of the spectrum.

Flushing the outboard with a mix of Heinz white vinegar. Note the hand cart outboard stand.

First up was getting the outboard off the boat, into the dinghy, out of the dinghy and mounted on the custom hand cart (phew!). One of the mounting clamps was seized and I broke the plastic handle getting it off. First repair: clean and grease the mounting bolt threads.

Then I ran the outboard in a mix of vinegar and water on the hand cart to clean out the water ways. A fresh rinse after made sure that no vinegar was left in the engine. Nothing much in the way of gunk came out.


Two thou feeler gauge on the inlet valve.

The first maintenance job was resetting the tappets. The plug was pulled to make it easier to find Top Dead Center. The plug had good color after 125 hours, and the gap was still in the specified range (of 0.031 - 0.034). I put in a new NGK plug nevertheless.

The book says 0.0024 thousandths for the tappet clearance on the inlet valve and 0.0043 thousandths for the exhaust valve. The top end is noisy on these engines and I had expected that the valve clearances were loose, but they were almost spot on (so I guess they are just noisy engines!).


Original plug still looking good

With the tappets out of the way, the next job was replacing the water pump with a new kit. This was fairly straightforward, but would have been difficult without the great how-to video that I found on youtube at https://www.youtube.com/watch?v=IHD8VdIj8TI. Thank you German Locomotion guy! The old impeller was still in good condition, but the old gasket had welded itself to the housing. I had to scrape it off with a scraper, and it was very stubborn. It had clearly not been assembled with any gasket goo, which really surprised me. I had the whole Tohatsu pump kit, so changed the pump body, bolts and gaskets.

Disassembled water pump. Old parts left, new parts in the box. Note old gasket stuck to housing.


Reassembled and ready to go. Also removed and greased the prop and splined shaft, replaced the prop cotter pin, and replaced the sacrificial anode.

When disassembling the lower unit, I noticed some wear marks half-way up the drive shaft. I did some internet research and discovered that there is a maintenance issue peculiar to extra long-shaft outboards. It turns out that the extra long drive shaft needs a self-lubricating bearing half way up the shaft to stop the drive shaft whipping around (see picture below). Unfortunately, the "self lubricating" bearings tend to dry out after 100 hours or so and can start to become noisy. The solution is to amply lubricate the bearing and shaft - which I did.


Mid shaft bearing and housing inside the outboard leg.

In order to access the mid-shaft bearing, I had to take off the housing extension just above the lower unit (again peculiar to the extra long-shaft model). I found that one of the housing bolts was completely corroded and frozen in place. I tried every trick in the book to get it undone including hitting it with a big hammer and a piece of wood. In the end it took heat judiciously applied to free the bolt from the housing. This confirmed a pattern in which the outboard appeared to have been assembled without lubricating the fasteners. I was very surprised at this because I have consistently found that Japanese built engines are of high quality and well put together. I wonder if the engines are imported in bits and locally assembled?



Next up was stripping and cleaning the carburettor. I viewed this video https://www.youtube.com/watch?v=oQELbAUZ53g to demystify the process - thank you "sumogurinet"! Unlike the water pump, I did not purchase a Tohatsu kit, so was unable to replace the needle valve and float. However, all of the gaskets were in good condition and the carb was very clean inside. I have used "Seafoam" fuel stabilizer in every tank of gas, and have always run the float bowl dry after using the outboard. This appears to have paid off and there was no gunk of any kind in the internals of the carb - the float bowl looked as new.


Carburettor refitted. Note the new fuel filter and refurbished fuel line clips.

One problem did arise in that all of the snap clips that hold the fuel lines in place were rusted. It amazes me that a company will go to all of the trouble to design and manufacture a complex machine with good materials so it can live in a saltwater environment, and then put cheap metal clips on the fuel lines! It makes me wonder, again, if the motors are assembled by a third party that has cut costs with hardware. I went to West Marine for replacement clips, but they didn't have any. So, I carefully wire brushed them clean, lubricated them with grease, and put them back on again.



Alternator wires come out the bottom of the outboard.

The last repair was the output wires from the alternator. They had soaked up water, corroded, and broken off. I stripped the wires back to clean copper, and fitted new marine connectors, and finished them off with heat shrink. The wires are fitted standard coming out the bottom the outboard, where they get blasted with water. After the repair, I have fitted them inside the outboard housing so that they will be sheltered from the elements.


The alternator wire connection will now be inside the housing.

The last job was firing up the outboard to make sure that it was all good. I managed to completely flood the engine and had to take the spark plug out to dry out the cylinder. Then a couple of pulls and it was running sweetly again. I boxed up the outboard in old boxes and cardboard to protect it and the boat, and then she was ready to go.

Wrapped and packed on Little Cat Too ready to take back to the boat


In summary: the outboard and all of the replaced and cleaned components were all still in good condition at 125 hours, and would have continued to work fine without replacement for probably quite a while. On the other hand, it was already tricky getting some of the fittings apart after 3 years, and this alone is a good reason to service the outboard at the correct time intervals. If fastenings holding the housings or any of the components together completely seize up, then the whole outboard could end up being a throw away, or parts only. For the Ultra Long-Shaft Sail Pro model in particular, there is the issue of the mid-shaft bearing which needs to be periodically lubricated to keep things healthy.


Things that actually needed fixing:
- seized bolt in mid-section housing
- stuck gasket under the waterpump
- seized mounting clamp
- lubricating the mid-shaft bearing and drive shaft
- rusty gas line clamps
- corroded alternator wires


Total Costs: $117.50
- 2 bottles of white vinegar $10
- NGK DCPR6E Spark plug $5
- Carburettor cleaner spray can $9
- Tohatsu water pump kit $44
- Tohatsu fuel filter $11
- Tohatsu anode $5
- Quicksilver outboard grease $13
- West Marine 80/90 lower unit oil $11
- Quicksilver 25/40 motor oil $9.50
- O/board shaft cotter pin

3 comments:

  1. Hey Roger,

    Are you still happy with your Dyneema inner lashings? I want to do this for (especially) rear beam, but I feel like the 1/8" may cut into the wood of my beams. What do you think?

    Brad

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  2. That is a very usefull information. I plan to get this excat model for my finally finisphed Tiki 21and will keep all this in mind. Thank you again.

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  3. Thanks so much for posting this...exactly what we need to know regarding the "self lubricating" bushing and especially the successful removal of the frozen bolt. Fair winds.

    ReplyDelete