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Tohatsu 9.8 100hr/6mo service

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awetmore
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Initially Posted - 07/30/2012 : 06:58:33

The manual [1] for the Tohatsu/Nissan 9.8A3 motor that I have recommends the following items be serviced every 6 months or 100 hours:
* motor oil change
* lower unit gear oil change
* inspect spark plug gap
* inspect timing
* inspect valve adjustment
* replace water pump impeller (every 12 months)
* clean/strip/adjust carb
* clean/replace fuel filter and lines
* thermostat check/replace
* inspect prop
* check anodes

I actually left a couple of items out, but that is a long list.

I've been searching the forums and the internet at large to figure out how to do some of these items (like checking valve clearance, inspecting the timing, and testing the thermostat). In doing so I've been seeing different recommendations on how often some of these items should be performed, for instance that the water pump impeller is good for 3-4 years.

I want to be a good owner and take good care of my equipment, but I also don't want to do work that isn't necessary. What are folks who've had these motors for a while doing as their every 6mo service and what are they doing less frequently? My motor is about a year old and so far I've only done oil changes.

Finally, does the service manual contain good enough instructions on how to check the thermostat, valve clearance, and timing? Has anyone found a good writeup for those steps online?

thanks,
alex

[1] Page 55 of http://www.tohatsu.com/tech_info/own_man_pdfs/Toh_MFS8A3_98A3_003-11082-6.pdf

Alex W
Seattle, WA
Express 37 "re-Quest"
previously owned 1984 Catalina 25 "Lutra"

Edited by - on

Davy J
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Response Posted - 07/30/2012 : 09:02:56

Think about how you use your motor. For me, 15 minutes on the way out, 15 minutes on the way back in. Even if I get out once a week, every week of the year, that equates to about 26 hours of use a year. My only real maintenance has been to change the motor oil. Water stream from impeller is still very strong, motor's four years old. Will probably change it and gear oil soon. I had to clean the carb a couple of times but only did so because low speed jet was dirty.

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awetmore
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Response Posted - 07/30/2012 : 09:33:31

I get out about 3 times per week on average, with most times having less than 15 minutes of motoring total. About twice a month I go out to the sound or Lake Washington and need to motor longer through canals that aren't well suited to sailing. My total motor hours per month are probably around 7-10. Most of my sailing and motoring is in fresh water (for this motor...my dinghy motor is an air cooled Honda BF2 that is almost exclusively used in salt water).

As my auto mechanic likes to remind me hours and miles aren't the only reason to change lubricants. A lot of short trips where the engine warms up and then cools down will promote condensation and getting water into the oil sump. From what I can tell the Tohatsu has zero or close to zero oil filtration. That is why I keep up with oil changes on a regular basis. My guess is that the gear oil should stay cool at all times (since it is under water and has a high amount of surface area), so that would be less of a concern.

That is why I'm asking what else people are checking during their regular service intervals. If inspecting the timing, valve adjustment, and thermostat is a quick procedure (hopefully someone with a service manual can answer that or tell me if the service manual is worth $50) then I'll do that as well.

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Sloop Smitten
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Response Posted - 07/30/2012 : 10:59:44

Of the list you provided the following do not sound like 6 mo/100 mile chores to me. More like three year chores and maybe not at all unless a problem was apparent.
* inspect timing
* inspect valve adjustment
* clean/strip/adjust carb
* clean/replace fuel lines
* thermostat check/replace
* replace water pump impeller
I do the rest every year.

Edited by - on

GaryB
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Response Posted - 07/30/2012 : 20:25:33

Keep in mind that the manufacturers set these guidelines based on motors they expect to be used approx. 4 hours per use, not 15 - 30 minutes per use. 100 hours in 6 months would be 16.7 hours per month.

I agree with Joe. Those items don't need to be changed for 2 or 3 years. When I was teenager we had a 100 hp Evinrude. We ran that motor for at least 500 hours (most at near wide open throttle) over a 5 year period and NEVER put it in the shop. We changed the gear oil, the plugs, and ran the carbs dry everytime. That motor NEVER gave us ANY problems. We might have changed the water pump once.

The 50 hp Mercury we had before the Evinrude ran like a top until my dad decided to clean and tune the carbs one time because it had a very slight miss when it was cold. He never could get it to run right after that until putting it in the shop and paying a small fortune to get it repaired.

Oil changes, fresh fuel, and keeping the engine cool will keep you going for a long time!

If it ain't broke, don't try to fix it!

Edited by - GaryB on 07/30/2012 20:27:34

OLarryR
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Response Posted - 07/31/2012 : 04:10:39

I was actually waiting to see how others would respond. I was too chicken to post at first. This is one of those areas where I find it hard to provide an opinion that differs from a mfrs prescribed scheduled maintenance out of concern that if something bad happens to your outboard, well then I would feel terrible for being part of the decision to stretch out certain maintenance. But here goes - Specific to what you listed, this is what I have done for my 2006 Honda 9.9 Xlong shaft which I use all year in fresh water (Potomac River):

motor oil change - Annual, Onboard, I suck it out with a vacuum pump
lower unit gear oil change - Every other year
inspect spark plug gap - No but instead usually replace annually.
inspect timing - Not yet
inspect valve adjustment - Not yet
replace water pump impeller(every 12 mths)- 6 yrs (replaced winter'11)
clean/strip/adjust carb - No
clean/replace fuel filter and lines - Annually
thermostat check/replace - Not yet
inspect prop - Okay, I see it has a small itty bitty ding. No work.
check anodes - It's there - No work.

Also - Change oil filter annually.

Here's the kicker - Since my boat is in all year-round, I have done everything while the outboard was still mounted to the bracket (except for the water pump impeller replacement which I did this past winter when my boat was out for the first time getting a blister repair/waterproofing. The engine oil can be sucked out thru the dipstick using a hand operated vacuum pump. Then taping plastic bag under the engine topworks as a catch for any residual drips, the fuel filter and oil filter can be changed out when the dock lines are oriented so the outboard is very close to the finger slip. The spark plugs can also be changed out at same time. The lower end gear case oil changeout is the tricky thing. Obviously best to accomplish with outboard off the boat and outboard in the vertical and I did it that way this past winter and one other time over 4 years ago when my boat was out for a week for a bottom painting. However, I have twice changed it while the boat was still in the water by tilting the outboard up and in that position and reorienting the dock lines, my outboard clears the finger slip and so I can work on the lower end on the finger slip but at an angle. I have found thru trial and error measuring the gear oil removed and oil added that I can practically all the oil out of the lower end even with the outboard tilted up. But the tricky thing is getting the oil back in. What I do is fill it as best I can in the tilted position and then lower the outboard back into the vertical after tightening the screw plugs. Then I tilt it back up again and add more oil with the outboard once again sloped over the finger slip. Then I lower it once again vertically. I believe I have then removed the top plug to see if I could see the oil at the top and have sometimes added oil with a thin tube. But you have to be extremely careful not to drop the screw plug into the drink doing it that way. I think I only removed the top screw plug one time in the oast when the outboard was back in the vertical above water but did not do it the last time I did it dockside this way because my previous experience was that adding oil when sloped above the finger slip pretty much got the oil all the way filled and when lowering it vertical to get any air bubbles to come up and then checking once again in the tilted, sloped position above the finger slip, hardly any addl oil had to be added.

Basically, my outboard has never been off my boat and except for this past wnter, my boathas always been in the water year-round. My outboard also runs flawlessly every year. So, I'm satisfied with my work-arounds toward maintenance. But maybe I need to look into the thermostat...that's one thing that has been off my radar screen. I will that out in my manual. I also have the shop manual for my outboard.

Edited by - on

awetmore
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Response Posted - 07/31/2012 : 06:10:38

Thanks everyone. It sounds like what people are doing is matching what I felt like I should be doing. I'd still love to know the instructions for checking timing and valve clearance if anyone has a service manual (even just knowing if that is covered would be good enough).

Larry: I also keep my boat in the water year round and have been doing my oil changes with a vacuum pump. I'm used to working this way, I've also been changing the oil in our VW TDI (diesel) cars for about 10 years using a vacuum pump. I haven't done the lower unit change yet, but I was going to make fittings that allow me to pump oil through there using a brake bleeding pump, that should allow me to get all of it more easily. I also considered just removing the lower unit and changing the gear oil on the hard, that also gives access to inspect the impeller.

It is interesting to know that the Honda 9.9 outboard has an oil filter. The Tohatsu does not (which seems strange to me). My Honda 2hp outboard doesn't either.

Edited by - on

dlucier
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Response Posted - 07/31/2012 : 06:17:52

My first boat came with a 17 year Johnson two stroke that ran like it just came out of the crate despite having the original seventeen year old spark plugs in it. Even though the plugs still looked great, I changed them out anyway. On my current Mercury outboard, I change the lower unit lube annually at the end of the season as it is easy, cheap, and if a seal starts to fail, I want to know about it sooner rather than later.

Edited by - dlucier on 07/31/2012 06:23:29

delliottg
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Response Posted - 07/31/2012 : 08:17:46

I too have been watching this thread. On our Tohatsu which has about 41 hours on it (according to the Tiny Tach), which means I've averaged just over 10 hours per year on it since new. I've changed the engine oil at the 10 hour break in point. I've cleaned or replaced all the fuel lines and filters, as well as added a Racor fuel/water separator, but that wasn't maintenance, it was repair after getting rusty water/gas from my phase separated metal fuel tank. I've replaced the spark plugs, and keep a spare set on board pre-gapped. I've rebuilt the carb 3x (again, repair, not maintenance). I have a spare impeller and plan to change it out over the winter. The engine still pees quite nicely so I don't think I'm in dire need to do so.

Right now it's running like a top, I'd hate to do anything to change that. I really don't like small engines, it seems like my whole life I've been dealing with one problem or another with outboards, lawn mowers, chainsaws, etc. That's one of the main reasons I bought the Tohatsu brand new, so I wouldn't have to deal with someone else's old engine troubles. So far, other than problems introduced by me, it's been very reliable.

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Sloop Smitten
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Response Posted - 07/31/2012 : 08:23:33

<blockquote id="quote">quote:<hr height="1" noshade id="quote">I'd still love to know the instructions for checking timing and valve clearance if anyone has a service manual<hr height="1" noshade id="quote"></blockquote id="quote">

Alex,
I have the service manual at home. (In the office right now.) I will check and see what they provide when I get home and let you know.

Larry,
Regarding the servicing of the prop, Honda recomends the prop be removed and the shaft cleaned, inspected and regreased with a marine grade grease each year. The shear pin should also be inspected. A new cotter pin is recommended as well. This assures if you do shear the pin the prop can easily be removed and will not have frozen to the shaft.

Edited by - on

OLarryR
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Response Posted - 07/31/2012 : 09:04:55

Joe - Good reasons for working the prop dis-assembly..so that it ensures when needed to be removed the prop is not frozen. I'll have to add that to my list of things to do.

David - Has a tiny tach ? Hmmm ! Did not know that some outboards come with that !

Don - 17 yr old spark plugs ! Wow ! Okay, the 4 strokes are more finicky than 2 strokes and probably a good idea to change the spark plugs more frequently but 17 yrs....me thinks I could then go at least 2 yrs or more on my spark plugs !!!

Also, I forgot to mention that I add either Startron or Stabil with every gas tank fill up.

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awetmore
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Response Posted - 07/31/2012 : 09:47:28

Tohatsu doesn't include a tach, but people add them. I keep meaning to get one. I'm pretty sure that I've put more hours on my motor in 2012 than David did since getting his, and the tach would help keep track of that.

I don't like to motor much, but getting out to the sound and back is at least 4 hours of motoring (often more like 5) and getting out to the Lake Washington and back is close to an hour of motoring. I'm lucky to live 10 minutes away from my boat and go sailing multiple times per week. I've met David (he was very helpful when I lowered my mast) and know that he has a longer commute to the boat and can't go quite as often.

This is my first (a second with the dinghy motor) small gasoline motor. We've always used push or electric lawn mowers and I've never owned anything like a scooter. The only other gasoline motor that I've owned is the one in my Subaru Impreza, our other cars have always been diesels.

Having dealt with 100k/10+ year old spark plugs on my car (soon after buying it used) means that I don't even want to repeat that with my outboard.

Edited by - on

delliottg
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Response Posted - 07/31/2012 : 11:24:41

<blockquote id="quote">quote:<hr height="1" noshade id="quote">David - Has a tiny tach ? Hmmm ! Did not know that some outboards come with that !<hr height="1" noshade id="quote"></blockquote id="quote">

Our Tohatsu didn't come with one, I bought it online from someone's suggestion on here and installed it myself (super simple to hook up). I think it was about $35 for the resettable version (not really seeing the value in the reset now, but seemed like a good idea when I got it).

It's true, my commute to the boat is a minimum of 40 minutes, and it's been longer than 2 hours. Plus right now, there's no direct way to even get to my marina due to construction. I've learned some back roads to get there, but even those keep changing as the construction progresses. So, just getting home afterward can be an adventure sometimes. I'm really looking forward to when they open the West Seattle Bridge completely back up. Last time I was at the boat was about 1-1/2 weeks ago for the late night cruise I wrote about. Was hoping to go crabbing yesterday, but the weather was pretty chilly, so we decided not to go.

When we do go out, it's probably less than 30-40 minutes of engine use per outing, enough to get us out of the marina and out to the bay, and the return trip. Maybe 15-20 minutes each way.

Similar to Alex, I've got three diesel vehicles, and if I could have found a small enough diesel outboard, I'd have gotten one. Unfortunately, they start at about 25 hp and they're BIG. My last gasoline vehicle was my Toyota truck that I sold when I bought my F-250 diesel. Although I miss that truck, we needed the diesel to tow the boat.

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Sloop Smitten
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Response Posted - 08/01/2012 : 08:11:23

Alex,
Sent you an email. Let me know if you did not receive it.

Edited by - on

mrapkins
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Response Posted - 08/01/2012 : 15:10:36

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Sloop Smitten
 <blockquote id="quote">quote:<hr height="1" noshade id="quote">I'd still love to know the instructions for checking timing and valve clearance if anyone has a service manual<hr height="1" noshade id="quote"></blockquote id="quote">

Alex,
I have the service manual at home. (In the office right now.) I will check and see what they provide when I get home and let you know.

Larry,
Regarding the servicing of the prop, Honda recomends the prop be removed and the shaft cleaned, inspected and regreased with a marine grade grease each year. The shear pin should also be inspected. A new cotter pin is recommended as well. This assures if you do shear the pin the prop can easily be removed and will not have frozen to the shaft.
<hr height="1" noshade id="quote"></blockquote id="quote">

There is no shear pin on a 9.9 Honda according to my Service/Shop manual.

Edited by - on

Sloop Smitten
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Response Posted - 08/01/2012 : 18:28:22

May be dependent on the year but my 1998 Honda 8 HP had a shear pin and I think that year the 9.9 and 8 were essentailly the same engine with some cam and jetting differences. The service manual for that engine recommended the greasing each year of the prop shaft.

Edited by - Sloop Smitten on 08/01/2012 18:29:18

OLarryR
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Response Posted - 08/02/2012 : 03:24:04

I did not have time yesterday to look thoroughly into my 2006 shop manual etc regarding supposedly no shear pin for the Honda 9.9. But I did come across a shifter pin that is in the lower end. Not sure if it serves same purpose. I also checked the troubleshooting pages but they do not have a flow chart on what if the outboard runs but the prop does not turn...so no help there.

Edited by - on

dlucier
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Response Posted - 08/02/2012 : 06:44:02

I thought shear pins were no longer used? My 17 year old Mercury doesn't use them.

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bigelowp
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Response Posted - 08/04/2012 : 14:53:43

Like many who have already posted, much has to do with how the engine is used etc, etc. I use my T-9.8 @ 10 hrs a season (I try to typically sail off the mooring) and the yard where I store the boat that is a Mercury dealer "services" the engine which is only changing the oil. They always say the engine is like new and does not need much -- although they have suggested the impeller be replaced this season (five years). If you read the annual service guidelines and then think through the use you put the engine through you may find that many tasks can be bi-annual or tri-annual. I am convinced the most important single task is to run the engine dry at the end of the season and make sure the gas used is clean and current.

The only ongoing issue I have with the engine is the engine case is always lose. I have changed the seal twice and can get most of one season when replaced. Have tinkered with the latches with little success. I am convinced that the "base" that the cover is attached to has a subtle dent. In any case a bungee is my assurance policy.

Edited by - on

TakeFive
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Response Posted - 08/04/2012 : 19:52:21

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Sloop Smitten
 May be dependent on the year but my 1998 Honda 8 HP had a shear pin and I think that year the 9.9 and 8 were essentailly the same engine with some cam and jetting differences. The service manual for that engine recommended the greasing each year of the prop shaft.
<hr height="1" noshade id="quote"></blockquote id="quote">
The Honda BF8 outboard (1998-1999 vintage) is a smaller displacement than the BF9.9. In that vintage, the BF9.9 and BF15 are "twins." My BF15 has no shear pin, and its BF9.9 twin does not either. The BF8 does have a shear pin. My BF15 (and its BF9.9 twin) does not have an oil filter either. According to BF8 manual, it also does not have an oil filter.

References:
[url="http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CE4QFjAB&url=http%3A%2F%2Fm.marine.honda.com%2Fpdf%2Fmanuals%2F31881805.pdf&ei=at4dUPPwHLTG6AG9nYGwDA&usg=AFQjCNGMLA1RPT_4cDXY5eiV4NnnCHzUuw&sig2=vNxOiLao9D_kNWjRyQ1M7w"]BF8 manual[/url]
[url="http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CGIQFjAC&url=http%3A%2F%2Fm.marine.honda.com%2Fpdf%2Fmanuals%2F31ZV4631.pdf&ei=Wt8dUO_ILMmJ6AHNr4G4Cw&usg=AFQjCNEcoazx6KUTr-pUvOn508rbne-iHw&sig2=L3TGFpqUjFIpZpoStG3DVw"]BF9.9/BF15 manual[/url]

I believe that oil filters were added to later Honda models after the redesign.

Edited by - TakeFive on 08/04/2012 19:52:44

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