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Tohatsu 9.9 HP versus 9.8 HP both 25" shafts - comparison and questions

E

Esteban

New member
[FONT=&quot]Hi All, This is my first post here. I came in hopes of getting some better answers to the following question I have. I am wanting to buy a new outboard for my 3500 lb Corsair 31 trimaran. Any opinions or experience on the following two similar outboards? Both are 4 stroke engines, with e-start, have 25" shafts and both have very similar power output, but there are some major differences.

The Tohatsu 9.8 has a carbureted 200+cc (smaller) engine and a 80 watt alternator and at 95 lbs is a savings of about 17 pounds over the 9.9 engine.

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[FONT=&quot]The light weight is very nice but I wonder if the smaller engine is higher stressed?
This carb version is easier to fix than EFI in the field but might be more of maintenance issue.
The smaller 80 watt alternator may be adequate, I am not sure.
The 9.8 costs a few hundred dollars less than the 9.9.

The Tohatsu 9.9 has an Electronic Fuel Injection 300+cc engine (same block at the 15 & 20HP), a 145 watt alternator and at a listed 112 lbs weighs 17 lbs more than the 9.8.
The EFI is attractive if it does not break down and will likely give better mpg. Is the Tohatsu EFI reliable?
The 145 watt alternator is also attractive.
The larger engine makes me think it will be less stressed and maybe last longer than the smaller 9.8.
The 9.9 costs a few hundred dollars more than the 9.8.

What are your opinions between the two engines and the points I listed above?
Should I expect one to last longer and be more reliable than the other?
I think its interesting that Tohatsu makes these two very similar HP output engines in their product line and I wonder why?

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Thank you for any light you can shed on this comparison.
Steve
 
They may eventually drop the 9.8, which is by far my favorite of all the Tohatsu 4-strokes. Lightest weight you can get in this size category. I used one for years (since 2007) on my 8000 pound HR-28 sailboat (with a 4-blade HT prop), and aside from normal oil, LU fluid, and WP servicing, it had no repairs until 2020. This year, it developed an intermittent starter relay, which was cheap and easy to repair in the field.

The 9.9 is cool in that it is essentially a detuned 20 (with a different ECU and a flow restrictor), so upgrading is possible, although the ECU is nearly $1K. The EFI is very reliable... quite similar to the 40/50/60, although those are 3-cylinder motors. The 9.9/15/20 is the replacement for the 15 and 20 carbed motors. Similar design and weight.

Of course, as with any carbed motor, it's advisable to either run the carb dry or drain it if it will be sitting for a week or two. On the EFI, drain the vapor separator for winter storage. If it were my boat, I would do the 9.8... cheaper, lighter, and a proven workhorse. They tend to start easier as well. As for durability, I have never seen a worn out 9.8 yet. However, if you need more charging, you will definitely want the 9.9.
 
Hi Paul,
Thank you for your answer. Do you think the EFI 9.9 is noticeably more fuel efficient?
Steve





pvanv said:
They may eventually drop the 9.8, which is by far my favorite of all the Tohatsu 4-strokes. Lightest weight you can get in this size category. I used one for years (since 2007) on my 8000 pound HR-28 sailboat (with a 4-blade HT prop), and aside from normal oil, LU fluid, and WP servicing, it had no repairs until 2020. This year, it developed an intermittent starter relay, which was cheap and easy to repair in the field.

The 9.9 is cool in that it is essentially a detuned 20 (with a different ECU and a flow restrictor), so upgrading is possible, although the ECU is nearly $1K. The EFI is very reliable... quite similar to the 40/50/60, although those are 3-cylinder motors. The 9.9/15/20 is the replacement for the 15 and 20 carbed motors. Similar design and weight.

Of course, as with any carbed motor, it's advisable to either run the carb dry or drain it if it will be sitting for a week or two. On the EFI, drain the vapor separator for winter storage. If it were my boat, I would do the 9.8... cheaper, lighter, and a proven workhorse. They tend to start easier as well. As for durability, I have never seen a worn out 9.8 yet. However, if you need more charging, you will definitely want the 9.9.
Click to expand...
 
Hi Esteban, I just upgraded my 36 foot sailing catamaran power from two 9.8's to 9.9's XLS. The 9.8's were still running flawlessly after six years service. The only issue i had was a clogged carburetor jet two years ago. I went ahead and had both carbs rebuilt and sonic cleaned with no issues since. I wanted a little more power for my cat as I charter in an area that often has thunderstorms in summer and in such situations you just cant get back to the dock quick enough sometimes, and the currents here can be pretty fierce as well. The 9.9's so far are noticeably more powerful. I haven't had time yet to really compare the performance because we are still breaking them in, etc. Fuel consumption seems to be about the same. One thing not mentioned was fresh water flushing after each trip. The 9.9's have a much more accessible flushing port. I had a small celebration when i shelved the earmuffs for good. Other than that, the 9.8's are like old friends.
 
When I bought my Tohatsu 20 HP for my cat around 2012 they were just bringing in the EFI models but still doing the carb versions. I chose the carb as I felt I had more possibility for fixing it if there became a problem miles away from base. I needed a new carb in 2017 despite always running it dry. There were hard white deposits in it that the Tohatsu agent said U/S cleaning would not remove. Having had petrol cars with fuel injection for 25 years without fuel issues I think I made the wrong choice!
 
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