Outboard size/weight trade off.

[Mikedefieslife]

I'm in the same situation as the OP except I know that I want an 8-10hp 2 stroke. Only problem is getting one.

I'm living aboard my boat so it's not like I can just bid for one and eBay and have it delivered. As has been pointed out, for new units you likely need to prove that it is for non-recreational use.

At the moment I make do with a little Mariner 2.5 that has the carb slide from a 3.5. In good conditions it can push me and 35kg dinghy up to around 7.5knts. Any load or weather and it's down to 5knts. Not really any good for exploring outside of the anchorage.

 

[seaangler23]

I’ve got a few outboards, using a 4s 5hp Suzuki on my honwave and getting 11kn and 8 with 2 on board, about as quick as a 5hp would go, have a 2.5mercury 2s on my other dingy and it still does 7, about 5 or 6hp is your limit for or a light engine as they will go to twin cylinder above this, if I was after a light engine I’d find an old Malta, use to run them on hire boats and they took all the abuse, the 4strokes seem to be very picky on fuel and I have to drain the carb on my Suzuki regularly, can’t find the reason why as it’s used daily but always runs again after, I have 2 and ones worse than the other

 

[SiteSurfer]

Thanks for all the replies, this forum is brilliant for providing a mixed but sincere range of observations and anecdotes.

I think that it's likely that I have a couple of choices left, I've looked at some second-hand engines but can't get over (in my head) the possibility of it breaking down mid-river with my daughter drifting away trying to start it.
That's true I suppose of a new engine, but the one we've had since new has never missed a beat and starts first-time every time - it's a comfort blanket.

Simply I am left with an electric version, either the ePropulsion or the Torqueedo 1003CS which leaves me with the obvious range issues - which, on the face of it are an issue, until I look at our usage over the last 4 years with the longest dinghy trip being up the into Beaulieu from one of the swinging moorings near the top of the river. Most trips are to and from the mooring (with the tidal issue as mentioned) which could be improved by simply making 2 trips with less crap in the boat - a journey of about 300m.

Finally I am left with the heavier 4 stroke powerplant. Given that the units are the same block it would make sense to go for a 5HP with FNR - I will go a do a test weigh in a dealer.

The only final option might be the smaller 3.5HP Tohatsu, but it seems a small difference to what I have.

 

[lw395]

There is some talk here of the OP repropping his little honda. These small engines are not like their larger brethren. Usually there is only the OEM prop size and pitch available even from re-sellers, so how is it that OP would be able to reprop?

Not so much about re-propping the Honda but understanding what the problem really is.
There definitely used to be alternative props which would fit the Yam Malta for instance.

If a spare prop could be obtained cheaply, one could reduce its diameter, which would allow the engine to rev more.

 

[SiteSurfer]

Tonight I was able to test weigh a Tohatsu 3.5 whilst chatting to a fellow yottie.

Same weight as my 2.8 Honda. So far so good. The chap said “reasonably reliable goes like the clappers.”

We followed each other to the waterline and he launched first, said to me “this is where my saying the engine is reliable will fail as it won’t start and I’ll drift down stream” obviously joking - what happened? Pulling for England and it wouldn’t start - that’s my nightmare scenario with my daughter trying start it.

The scope is narrowing.

 

[CLB]

Tonight I was able to test weigh a Tohatsu 3.5 whilst chatting to a fellow yottie.

Same weight as my 2.8 Honda. So far so good. The chap said “reasonably reliable goes like the clappers.”

We followed each other to the waterline and he launched first, said to me “this is where my saying the engine is reliable will fail as it won’t start and I’ll drift down stream” obviously joking - what happened? Pulling for England and it wouldn’t start - that’s my nightmare scenario with my daughter trying start it.

The scope is narrowing.

You are always gong to get that with any outboard, new or old, four or two stroke. I have even known Torqeedos to cause problems, although there is no pull start to worry about obviously. Get some oars and teach your daughter to row.

 

[Iliade]

Even my nearly now 3 y.o. Yamaha 4T can be a pain to start some times. They have the most microscopic idling jets which can block easily. Fortunately the carb is pretty easy to remove and clean and often just draining the fuel chamber does the trick. I fear modern 'petrol' may have something to answer for here.

When it is working normally, the starting pull involves a slightly different technique to a two stroke; The pull is longer, more even and highly pressured. After nearly forty years playing with outboards I have just worked out that having my hand palm upwards causes less bruising in between my fingers than palm down. I also brace the pulling hand with my other one if a second pull is required.


One is supposed to be able to lay it down in any orientation, but if the gearbox gets elevated the oil falls out. That has probably improved the life expectancy of the rest of the motor though.

It weighs much the same (anecdotally) as the remanufactured ex-military Mariner 2T 20hp I bought from Russell Simpsons to replace it in its primary role as a lake-based safety boat motor. The 2T will not idle anywhere near as nicely, but pushes the tub (Jeanneau Nematic 360) along at >20kt, rather than the ~12kt achievable with the 4hp.

If you want your motor to be reliably started by a weaker person, electric start is probably the only guarantee(ish)

 

[geem]

Even my nearly now 3 y.o. Yamaha 4T can be a pain to start some times. They have the most microscopic idling jets which can block easily. Fortunately the carb is pretty easy to remove and clean and often just draining the fuel chamber does the trick. I fear modern 'petrol' may have something to answer for here.

When it is working normally, the starting pull involves a slightly different technique to a two stroke; The pull is longer, more even and highly pressured. After nearly forty years playing with outboards I have just worked out that having my hand palm upwards causes less bruising in between my fingers than palm down. I also brace the pulling hand with my other one if a second pull is required.


One is supposed to be able to lay it down in any orientation, but if the gearbox gets elevated the oil falls out. That has probably improved the life expectancy of the rest of the motor though.

It weighs much the same (anecdotally) as the remanufactured ex-military Mariner 2T 20hp I bought from Russell Simpsons to replace it in its primary role as a lake-based safety boat motor. The 2T will not idle anywhere near as nicely, but pushes the tub (Jeanneau Nematic 360) along at >20kt, rather than the ~12kt achievable with the 4hp.

If you want your motor to be reliably started by a weaker person, electric start is probably the only guarantee(ish)

In my experience small outboards whether two stroke or four stroke are more trouble than larger ones. What is even stranger is that a Tohatsu 9.8 hp 2stroke is easier to pull than a smaller four stroke or two stroke. Same can be said of a Yamaha Enduro 15hp 2stroke. So easy to start. My wife always had trouble starting the 6hp mercury 4stroke but found the bigger engine easy. In your case a Tohatsu 9.8hp 2stroke would be a great solution. We found we used less fuel than smaller engines as you got on the plane with the 9.8 and then throttle back. Smaller engine never got on plane with any load in it so used a ton of fuel. You find with a bigger engine you go places because you can. We dont think anything of gping a few miles in the tender when you are doing 15kts. You really cover the miles and get to explore places you wouldnt with a little egg wisk engine

 

[Graham376]

Agreed, I've always found the Tohatsu 9.8 to be a very reliable engine. It'a twin 2 stroke so, compared to a 4 stroke single which fires once every 4 strokes, each cylinder fires alternatively every 2 strokes so, in effect, it has 4 times as many firing strokes for every pull on the cord.

 

[charles_reed]

Thanks, VicS I did some reading and found that Tohatsu is a common badged brand.

My 2.3 is 13KG and generic 5HP's seem to be around the 25-28Kg mark so double the weight.

My question (perhaps poorly phrased?) was in real life, how folks found whether the increase in 2HP was actually worth the weight increase, given that I'm so far from the sea/boat - trying something out isnt really an option, even when we bought the 2.3 from a dealer - there wasnt really an option to test first.

I'm afraid you're right - the air-cooled Honda is significantly lighter than any of the other 4-stroke engines - for that reason I'll only use a 2-stroke - lots for sale 2nd hand and easily bought as "grey" imports in the Med. The 3.5hp Tohatsu/Mariner/Mercury only weights 14kg.

 

[Mikedefieslife]

I'm afraid you're right - the air-cooled Honda is significantly lighter than any of the other 4-stroke engines - for that reason I'll only use a 2-stroke - lots for sale 2nd hand and easily bought as "grey" imports in the Med. The 3.5hp Tohatsu/Mariner/Mercury only weights 14kg.

Where are the links to these 2 strokes for sale in the Med as I haven't found any even when asking around engine repairers and 2nd hand places.

 

[Snowgoose-1]

I'm afraid you're right - the air-cooled Honda is significantly lighter than any of the other 4-stroke engines - for that reason I'll only use a 2-stroke - lots for sale 2nd hand and easily bought as "grey" imports in the Med. The 3.5hp Tohatsu/Mariner/Mercury only weights 14kg.

That's good to know, ref 3.5 hp but they are probably wash and go where the Honda can idle in neutral gears. For power and gears you have to go to the heavy. Fine if is a hooded Mexican wrestler is doingheavy lifting but for the rest of us have to leave on the dinghy. Is their another sport that does not have as many compromises ?

 

[coveman]

I'm in the same situation as the OP except I know that I want an 8-10hp 2 stroke. Only problem is getting one.

I'm living aboard my boat so it's not like I can just bid for one and eBay and have it delivered. As has been pointed out, for new units you likely need to prove that it is for non-recreational use.



At the moment I make do with a little Mariner 2.5 that has the carb slide from a 3.5. In good conditions it can push me and 35kg dinghy up to around 7.5knts. Any load or weather and it's down to 5knts. Not really any good for exploring outside of the anchorage.

An 8hp Yamaha 2 stroke may suit you. Fairly light at 28kgs and have a twin cylinder robust engine so they are relatively quiet and smooth in operation - the only problem as you say is finding one - decent ones do crop up from time to time but they now command a premium due to their simplicity and light weight. Perhaps worth leaving your name with a dealer in case they have anything turning up?

 

[Graham376]

Looking back at the OP's original question and the many replies, there's a danger that he's likely to spend money with no benefit. He wants a faster 2.9 dinghy with 3 people + luggage.

We had a Yam Malta (3.5hp IIRC) on the identical dinghy, 2.9m with airdeck. It was rather slow so we traded that in and bought the Suzuki DF6 which planed with 2 up but just dug a deeper hole than the Malta with 3 or 4 people on board. A lot heavier and expensive, certainly not worth it. For what he wants, I think a waste of money going for another smallish engine.

P.S. Even the 9.8 won't plane with 3 or 4 people + luggage but it's a hell of a lot more fun 2 up + bikes etc.

 

[CLB]

That's good to know, ref 3.5 hp but they are probably wash and go where the Honda can idle in neutral gears. For power and gears you have to go to the heavy. Fine if is a hooded Mexican wrestler is doingheavy lifting but for the rest of us have to leave on the dinghy. Is their another sport that does not have as many compromises ?

The 3.5 has forward and neutral gears.

 

[charles_reed]

Where are the links to these 2 strokes for sale in the Med as I haven't found any even when asking around engine repairers and 2nd hand places.

I've got 2 on offer here in Kalamata (both 2nd hand) and know of two yards in Malta who will source 2-strokes for you.

Why not rise off your posterior and do your own work?

 

[charles_reed]

That's good to know, ref 3.5 hp but they are probably wash and go where the Honda can idle in neutral gears. For power and gears you have to go to the heavy. Fine if is a hooded Mexican wrestler is doingheavy lifting but for the rest of us have to leave on the dinghy. Is their another sport that does not have as many compromises ?

Obviously a misapprehension - the Tohatsu-based 3.5/3.3 all have a dog-clutch with forward neutral.
Getting them to idle is a matter of careful adjustment of the slow-running jet.
The Honda may be a very fine engine (but air-cooled not a good idea in hot places) and it is noisy and feeble.
If the OP is looking for a planing engine - success has as much to do with the inflatable design as the engine. The 3.5/3.3 Tohatsu will just plane a 2.4 RIB with one up, struggles with an inflatable V floor and has no chance with a conventional dinghy. Interestingly the RIB is easily the heaviest.
If, as I suspect he is, hankering after a planing dinghy with 3 up, he's got a long way to go and probably needs about 11-15 hp. I doubt the dinghy is designed for such power outputs!!!
Maximum designed power outputs are clearly stated on the dinghy transom plate.

 

[Graham376]

Maximum designed power outputs are clearly stated on the dinghy transom plate.

Strangely, my Waveline 2.9 with ply floor is rated at 10hp max but the new ones are only rated at 6hp. Marathon, the distributors couldn't give a reason for this.

 

[SiteSurfer]

Just to clarify. I don’t need my 2.9 to plane - it’s just that it struggles with a heavy load - quite possibly I may be after the unicorn of outboards

 

[Capt Popeye]

Strangely, my Waveline 2.9 with ply floor is rated at 10hp max but the new ones are only rated at 6hp. Marathon, the distributors couldn't give a reason for this.

Might I ask, is that weight /power adjustment for the Newish 4 stroke engines ?