BLUF: Go for a
2 stroke for lightness, durability, and repairability (and no timing belt), or EFI for
reliability.
My friend and I both have a
Nissan 15hp
4 stroke, which it's exactly the same as the Tohatsu 15 but with a dark blue
paint and different stickers. It is carburated and both of us have so many issues with the carb from fuel. I guess we just don't use it enough? We both run them dry when done, always use fuel stabilizer (can't get ethanol free fuel here). For $200 for a new carb, this time it's not worth
cleaning. I'm pretty sure that's not the same motor as the 9.8hp Tohatsu though, so this is just anecdotal. I'm looking to replace it for either a
2 stroke, or a lighter model with EFI as it's 120lbs and too heavy to put on the railing.
The Tohatsu 9.9EFI is the same as the 15 and 20, and the same as the 15 and 20 Merc (Merc doesn't sell it as a 9.9?). So they all weigh around 95lbs. Suzuki also makes small EFI motors, weighing about the same. They are not built by Tohatsu. If you go with the EFI, it's about $500 for a new ECU and the restrictor in the intake to go up in
power.
Personally, I'm tired of dealing with taking out the carb,
cleaning it, losing
parts, busting my knuckles. I just want an engine that starts! My 2 stroke Merc 25 (2001) has been giving me range anxiety because the carb, and something else in the ignition system is screwed up (and intermittent). I also have a vacuum leak somewhere, so I need an external
electric fuel pump to keep it running. I haven't put the
boat in the
water since 2017 because I don't trust the outboard anymore. I'm looking to replace that one with a 25hp Suzuki. Even though it's significantly heavier (125 vs 155) and I'd love to keep it, the cost to get it to the point I trust it is growing. And not having to deal with the carb anymore may well be worth it (plus I get
power tilt and trim). I won't even notice the reduction in speed because I'm pretty sure the Merc isn't making 25 hp anymore. Plus, you can
plug the EFI motors into a computer to help diagnose. That's a big plus in this "remove and replace" days of
repair instead of actually diagnosing the problem. After paying a Merc dealer to try and solve the problems (apparently by R&R), I'm left with a less reliable motor than when I gave it to them.