Best small petrol 4 stroke 3 or 4 h.p dingy outboard motors

[RJMRJM]

My apologies to the readers. In an earlier reply I said my outboard was an ISUZU it is not It is a Tohatsu RJM

[Dockhead]

So as it turns out the new Mercury (probably stencil branded Tohatsu) propane outboards are available in Europe:

https://on-yacht.com/motoren/fourstr...ussenbordmotor

I like this. No more carburetor problems. No more carrying another fuel -- can use the same gas bottles I use for cooking.

The only issue is this. At 5hp it's too small for much planing. Maybe only if there is only one person. Yet it weighs 27kg -- so MUCH more awkward to take off and put on than the 18kg Mercury 3.5, or the various electric outboards. No problem for those with outboard cranes, but I would have to use block and tackle from the boom end.

It weighs the same as my old 8hp Selva, which WOULD plane the dink with two people on board. So I think it's an awkward in between size. If I were happy to use a block and tackle every time, then I think I'd rather have 8hp or 10hp

[goboatingnow]

Originally Posted by mlydon

Yamahas are the best of the best, but cost it. Tohatsu 3.5 4 stroke will do fine, and reasonable price. The trick is, run it out of fuel every night - turn off the stop cock or disconnect the fuel line and let the motor run until it quits. This keeps the carb clean - a modern 4 stroke sips so little fuel that the jets are tiny. Leaving fuel in the carb attracts water, then the fuel evaporates, leaving water behind, which gunks everything up.

Matt

It’s not practical to run them dry every day.

Just dose ( actually overdose ) with a fuel treatment /cleaner additive ( I use mercury ) , this will keep the jets clean. No need to remove fuel. End of season drain everything

Move runs like a sowing machine since I started this , starts first pull and idles forever

[Sailmonkey]

Originally Posted by RJMRJM

I have been told that the old Tohatsu 2 stroke is the best of the small 3.5 HP 2 stroke motors has anybody had any experience in this area. RJM

I’ve got a pair of older two strokes both tohatsu. One disguised as a mariner 5hp, one of unidentifiable rebranding.

The 2hp can sit for years with a carb run dry, then start immediately when requested. The 5hp is a little more finicky, usually requiring the float valve to be cleaned after a year of inactivity, then running flawlessly daily for months on end.

[sailhand]

Best of the best small two stroke l have ever used is the 3hp yamaha. Has the throttle on the tiller not a slider like the tohatsu. Starts easiest of all outboards I have ever owned and is by far the most reliable. The 3.5 four stroke tohatsu/mercury etc is a great little motor but the fuel/carb issue requires constant care. Definitely dont use ethanol fuel, use a good fuel additive and monitor/add extra fuel filter. Clean fuel and you have no problems. If you use the dinghy daily fuel is not usually an issue. If using any less than weekly I run them dry and turn off all fuel taps and breathers on fuel caps. The breather allows air to condense inside the tank of a evening creating water droplets which then run down to the bottom of the tank. They accumulate over time as they cannot evaporate under a layer of petrol. This is a common way to get water into your tank and the reason I always close the breather as well as the fuel tap. Ethanol fuels absorb moisture from the air in humid, read marine environment, conditions. The two main causes of carb problems in my experience are water and varnish from evaporated fuel when stored. The fuel varnish forms a hard crust in the carb bowl and when you subsequently start using the motor the varnish will slowly break down and form small solid particles that find their way into the tiny jets on these small four strokes. On my four stroke 3.5 mercury/tohatsu/mariner/evinrude etc l upgraded the carb to the larger 5hp version. There are upgrade kits online however I bought a 40 dollar carb on ebay and have had good results so far. The 3.5 two stroke tohatsu is not one of my favourite motors, in fact its almost on the bottom of my list. It is one of the lightest for the most power but not relable in my opinion. The twin cylinder 4hp omc motors from the 90s are the lightest most powerful sub 4hp motors I have used. I have 5 of them in my shed. The problem I have with them is access to parts and access to the carb when on the water. The best motor for on water access to drain the carb is the small four strokes as the carb is mounted higher affording easy access. They are really simple to remove strip and clean which will be necessary at some point with all outboards. Outboard mechanics will tell you that 95% of their work is fuel problems. Its amazing how many cruisers outboards I have cleaned the carbs on only to see them full of dirt and water a few weeks later. These guys always assure me the fuel they use is not the problem but clearl it is. I never use the last litre of fuel in a drum. I always try and keep the fuel drum settled when decanting fuel so as to keep any contaminants in the drum settled at the bottom. I often see people shake a drum before decanting the last bit of fuel out into their outboard. This is like getting a handful of dirt and a cup of water and tipping it into your carb, not a good idea. Cheers

[WaldPinkler]

I had a tohatsu 9.8 and a yamaha 2.5 both 4 stroke. The yamaha was much easier to work on. All the bolts were the same size so just one socket.

I've since bought a yamaha 6hp. Updated version of the 2.5. Looks even easier to remove the carb.

I looked at mercury and suzuki which are the 3 major ones. All about the same build and price. Suzuki a bit lighter but not sure where they save weight. Went with yamaha because parts are more available. Even a service center in Papua New Guinea.

If you're not going afar, just pick one of the big brands. There isn't a huge difference between them.

[Dockhead]

Originally Posted by sailhand

Best of the best small two stroke l have ever used is the 3hp yamaha. Has the throttle on the tiller not a slider like the tohatsu. Starts easiest of all outboards I have ever owned and is by far the most reliable. The 3.5 four stroke tohatsu/mercury etc is a great little motor but the fuel/carb issue requires constant care. Definitely dont use ethanol fuel, use a good fuel additive and monitor/add extra fuel filter. Clean fuel and you have no problems. If you use the dinghy daily fuel is not usually an issue. If using any less than weekly I run them dry and turn off all fuel taps and breathers on fuel caps. The breather allows air to condense inside the tank of a evening creating water droplets which then run down to the bottom of the tank. They accumulate over time as they cannot evaporate under a layer of petrol. This is a common way to get water into your tank and the reason I always close the breather as well as the fuel tap. Ethanol fuels absorb moisture from the air in humid, read marine environment, conditions. The two main causes of carb problems in my experience are water and varnish from evaporated fuel when stored. The fuel varnish forms a hard crust in the carb bowl and when you subsequently start using the motor the varnish will slowly break down and form small solid particles that find their way into the tiny jets on these small four strokes. On my four stroke 3.5 mercury/tohatsu/mariner/evinrude etc l upgraded the carb to the larger 5hp version. There are upgrade kits online however I bought a 40 dollar carb on ebay and have had good results so far. The 3.5 two stroke tohatsu is not one of my favourite motors, in fact its almost on the bottom of my list. It is one of the lightest for the most power but not relable in my opinion. The twin cylinder 4hp omc motors from the 90s are the lightest most powerful sub 4hp motors I have used. I have 5 of them in my shed. The problem I have with them is access to parts and access to the carb when on the water. The best motor for on water access to drain the carb is the small four strokes as the carb is mounted higher affording easy access. They are really simple to remove strip and clean which will be necessary at some point with all outboards. Outboard mechanics will tell you that 95% of their work is fuel problems. Its amazing how many cruisers outboards I have cleaned the carbs on only to see them full of dirt and water a few weeks later. These guys always assure me the fuel they use is not the problem but clearl it is. I never use the last litre of fuel in a drum. I always try and keep the fuel drum settled when decanting fuel so as to keep any contaminants in the drum settled at the bottom. I often see people shake a drum before decanting the last bit of fuel out into their outboard. This is like getting a handful of dirt and a cup of water and tipping it into your carb, not a good idea. Cheers

This is great information; thanks.


I'm hating my 3.5 Mercury a little less this summer. I'm using it almost every day, and it's working ok. I've finally learned how to transition it from choke on to choke off -- you have to open the throttle to a certain position before pushing it in.


I guess you just have to get comfortable with frequently pulling the carb off, which is not a complicated operation. Put a filter in line, and use alkyd fuel before taking it out of use for more than a week. Bit of a faff, all that, but maybe worth saving the investment in electric, at least this year.


I still think small 4 strokes are really a lot of trouble compared to other small outboards. It's really too bad we can't buy two strokes any more.

[Pete7]

Originally Posted by Dockhead

I still think small 4 strokes are really a lot of trouble compared to other small outboards. It's really too bad we can't buy two strokes any more.

There is one solution to the problem, but it means a detour to Alderney for a 2 stroke 3.5hp Tohatsu.


https://mainbrayce.co.uk/tohatsu-3-5hp/

We love our little Honda 2.3Hp and since small outboards in this range won't plane a small dinghy it suits our needs. A carb clean once a year seems to do the trick.

Pete

[Dockhead]

Originally Posted by Pete7

There is one solution to the problem, but it means a detour to Alderney for a 3.5hp Tohatsu.

https://mainbrayce.co.uk/services/

Right. Hot tip.


The big question for a dinghy like mine (light weight folding RIB, 11 feet) is do you want to plane it, or not?


If you are ok not planing it -- and I cannot with 3.5hp -- then a Torqeedo would the best solution, if you don't consider the cost.


If you want to plane, you need at least 8hp, better 10hp. A lightweight 10hp two stroke would be ideal for that.


Unfortunately Tohatsu two stroke 10hp weighs 37kg -- like a four stroke, . 6hp is 25kg. My four stroke Selva 8 is 27kg.



Only Tohat two stroke which is really interesting for my use case would be one of the small ones -- the 3.5, which weighs the same as my Merc 4 stroke, but would probably be much more reliable.


For non-planing application I would probably still prefer electric.

[WaldPinkler]

My cheap 2.5m air deck inflatable planes with 6hp yamaha. Not with 2 though.

[Dockhead]

Originally Posted by WaldPinkler

My cheap 2.5m air deck inflatable planes with 6hp yamaha. Not with 2 though.

It's a real condundrum.


EITHER a motor you can lift and carry yourself, OR planing ability.


I think I'm going to bring back my 8hp Selva, then replace the 3.5 Merc with a Torqeedo. Use the Torq for usual short distance ferrying, the Selva for longer range stuff. Sell the Merc. But not this year.

[Pete7]

Originally Posted by Dockhead

I think I'm going to bring back my 8hp Selva, then replace the 3.5 Merc with a Torqeedo. Use the Torq for usual short distance ferrying, the Selva for longer range stuff. Sell the Merc. But not this year.

Torq, so last year

You need the Spirit with remote control and regen


https://epropulsion.uk/spirit-1-0-evo/

[Dockhead]

Originally Posted by Pete7

Torq, so last year

You need the Spirit with remote control and regen


https://epropulsion.uk/spirit-1-0-evo/

Yeah, I like the EProp ones very much. Regen not needed on a dinghy, but this still has some advantages. I think the two top contenders are Torq and EProp.

[WaldPinkler]

I kept my old 2.5hp. If I'm cruising then it's a pain to put a larger engine on and off just to get to shore. I can hold it one handed and step down off the side of the boat (no swim platform).

The 6hp is a bit heavy for that. I kind of wish I got a 10hp though. Then planing with 2 is possible.

[rslifkin]

Regarding the choke/throttle relationship on the Tohatsus (and Merc and Nissan versions), if you pull the choke knob with the cowl off you'll notice that applying choke also opens the throttle a bit. So it makes sense that it may need a little throttle as you back the choke off unless you do it very slowly and make sure it's plenty warm enough first.

With small 4 stroke land engines, I've had good luck with carbs by adding stabilizer to any fuel I buy right away. And then if it's going to sit for more than a few weeks, drown it in fogging oil at shutdown. Keeping the carb oily seems to do the trick. I don't run the carbs dry when I do that and generally leave fuel in the tank for the off-season too. So far, I've yet to have anything not just fire right up (with some smoke) and run perfectly when it's needed.

I just picked up a 6hp Nissan (Tohatsu) 4 stroke. It's ~8 years old, no idea how it was treated previously. But it hadn't been run since last year, was still full of fuel, etc. No carb issues on startup, although I noted it was smoky. Turns out the internal fuel tank was full of 2 stroke pre-mix. I'm betting the oil was enough to keep the carb from gumming up. We'll see if my normal methods work on that carb as well.