Worth upgrading to a 4 stroke o/b?

[Kelpie]

I use a 27yr old 2.5hp 2 stroke on my tender. I've removed the restrictor in the carb so in theory it's now a 3.5hp?

I've been toying with getting a slightly bigger motor but on balance it's probably not worth it. The dinghy is not designed to plane and we can reach 5-6kt, slightly more if I'm on my own. I'm not sure if more power would do all that much.

If I swapped for, say, a Honda or Suzuki 2.3/2.5hp 4 stroke, I wouldn't be adding any weight. But would I be losing a noticeable amount of power? And how much extra fuel efficiency would I get?

 

[[2574]]

I use a 27yr old 2.5hp 2 stroke on my tender. I've removed the restrictor in the carb so in theory it's now a 3.5hp?

I've been toying with getting a slightly bigger motor but on balance it's probably not worth it. The dinghy is not designed to plane and we can reach 5-6kt, slightly more if I'm on my own. I'm not sure if more power would do all that much.

If I swapped for, say, a Honda or Suzuki 2.3/2.5hp 4 stroke, I wouldn't be adding any weight. But would I be losing a noticeable amount of power? And how much extra fuel efficiency would I get?

Depending upon how you use the dink - I would thoroughly recommend an electric outboard. Transformational.

 

[Slowboat35]

Electric outboards are transformational on your bank account too...

 

[Refueler]

Fuel economy ? How many hours running does it get ? How much fuel do you presently use ?

Where do you store the O/bd on board - can you lay it down as required ?

Is the present O/bd suffering age or problems ?

Service costs ?

If you asked around your local boaters who would like to buy your 2str .... bet you'd be crushed in the rush !!

 

[geem]

I use a 27yr old 2.5hp 2 stroke on my tender. I've removed the restrictor in the carb so in theory it's now a 3.5hp?

I've been toying with getting a slightly bigger motor but on balance it's probably not worth it. The dinghy is not designed to plane and we can reach 5-6kt, slightly more if I'm on my own. I'm not sure if more power would do all that much.

If I swapped for, say, a Honda or Suzuki 2.3/2.5hp 4 stroke, I wouldn't be adding any weight. But would I be losing a noticeable amount of power? And how much extra fuel efficiency would I get?

If you are in the Caribbean you don't need to buy 4 stroke. In Sint Maarten you can buy new Tohatsu 2 strokes engines.

 

[Kelpie]

If you are in the Caribbean you don't need to buy 4 stroke. In Sint Maarten you can buy new Tohatsu 2 strokes engines.

Aware of that, but if I'm only going for a tiny engine I'm not sure there's any advantage in a 2t? The Honda and Suzuki weigh about 13kg. No more mixing up fuel and presumably better fuel economy?

 

[Kelpie]

Fuel economy ? How many hours running does it get ? How much fuel do you presently use ?

Where do you store the O/bd on board - can you lay it down as required ?

Is the present O/bd suffering age or problems ?

Service costs ?

If you asked around your local boaters who would like to buy your 2str .... bet you'd be crushed in the rush !!

We're currently cruising the Caribbean, so it's getting a lot of use. In Europe I just rowed everywhere but the distances are greater here. Dinghy fuel is becoming a noticeable expense.
The engine lives on the back of the dinghy most of the time, which is lifted on davits. The extra weight of a bigger engine would mean I'd have to remove it every night which would get old very quickly.

 

[Kelpie]

Depending upon how you use the dink - I would thoroughly recommend an electric outboard. Transformational.

I'd love to try one out.
My 2t works just fine but it's very noisy and has no neutral which makes for interesting close quarters manoeuvring.

 

[johnalison]

I changed my 2.2 2-stroke Suzuki for a 2.5 4-stroke and the new one seemed to have a lot more shove. I think that if you just want a tender-pusher and not a planer you will be quite happy with it. Although not perfect in all ways, the 4-stroke ran smoother without the faff of adding oil, and was easier to carry.

 

[NormanS]

I changed from a 2.5 Mariner 2 stroke to a 2.5 Honda air cooled 4 stroke. There were two main reasons:
1. The Mariner was never reliable at starting. It was pretty ancient.
2. The normal pattern of use was that the outboard was used to go out to the boat on the mooring, and was then often not used at all, we preferring to row shore. This meant that the outboard often sat for weeks with drying out salt water crystallising in its water galleries.

The Honda always starts right away (once the carburettor is full). Being air cooled means no problems associated with its storage aboard. No mixing of fuel.
As a treat for our old age, I made a davit for lifting it on and off the dinghy. I should have done it years ago! It has revolutionised our use of the outboard.

 

[dunedin]

Personally I would stick with the lightweight 2 stroke. Indeed last year we got an old 3.3hp Mariner to replace/complement the existing Mariner 2.5hp, but only because the neutral was better for young grandkids who are starting to assist in the dinghy.

 

[PetiteFleur]

I changed from a Suzuki 2.2 2stroke to a Honda 2.3 a few years ago. Certainly easier starting BUT it is heavier and bulkier. Service it yearly, but now always use E5 petrol and Honda additive as had problems last year with outboard, strimmer, lawnmower and small generator - as petrol had gone 'off'... If I could get a small 2 stroke again then I would be tempted as lighter etc(been told it's something to do with getting older...)

 

[geem]

Aware of that, but if I'm only going for a tiny engine I'm not sure there's any advantage in a 2t? The Honda and Suzuki weigh about 13kg. No more mixing up fuel and presumably better fuel economy?

I have found in the past that a decent rib with a 10hp Tohatsu used less fuel than an inflatable dinghy with a 3.5hp doing the same distances. The 3.5hp with 2 people in would be almost flat out where as the 10hp on a planing hull was more fuel efficient. Low revs and not having to work hard to stay on the plane. I don't think there is much difference between two stroke carburettor and four stroke carburettor fuel consumption., except you also have to buy 2 stroke oil. Once you get to fuel injection then the difference in fuel consumption is quite noticeable.
For me the small two stroke wins hands down. They aren't as sensitive about the fuel you give them. There is a lot less to go wrong. They don't need oil changes. They are generally lighter.

 

[robmcg]

Have both a 2.5hp Mariner 2st and a Honda 2.3 4st. Both are good in their own way. Most noticeable difference is fuel economy. The Honda is very frugal on fuel. Now we rarely run it at full chat but the last season we did in Scotland we used just over 5 litres of petrol.............for the whole season . The Mariner probably would have used almost twice that for the same amount of mileage.
I am not a fan of the Honda centrifugal clutch, or the noise it makes but that's a separate issue.

 

[geem]

Have both a 2.5hp Mariner 2st and a Honda 2.3 4st. Both are good in their own way. Most noticeable difference is fuel economy. The Honda is very frugal on fuel. Now we rarely run it at full chat but the last season we did in Scotland we used just over 5 litres of petrol.............for the whole season . The Mariner probably would have used almost twice that for the same amount of mileage.
I am not a fan of the Honda centrifugal clutch, or the noise it makes but that's a separate issue.

One of the OPs problems here in the Caribbean is the distance between your anchored boat and the town dock, beach, bar or restaurant. They are quite often
100s of metres away. Places like Jolly Harbour are a mile from anchorage to dinghy dock. Not only that, its windy here. The last few days it has been blowing 18/35kts. The fetch of a few 100 metres soon kicks up a chop and in a small deflatable and egg wisk engine the journey get tiresome after a while. You get wet, the shopping gets wet and the trip ashore seems less appealing.
Most cruisers that spend time in the Caribbean splash the cash and opt for a 10 or 15 hp 2 stroke and a 9 or 10ft rib. A rib becomes like your car. It needs to carry everything to and from your boat for several months. There are few marinas and they are usually stinking hot and buggy. So much nicer to be out at anchor but you need good transport.

 

[robmcg]

We clock up quite a few miles in the dinghy in Scotland too. Rarely a flat run ashore. Unfortunately my back wouldn't tolerate shifting a big outboard around so an egg whisk it is

 

[Neeves]

In less developed or isolated parts of the world 2t are de rigour and parts and servicing easy. The 2 stroke will be lighter and easier to lift from dinghy to the mothership. I'm not sure of the regular complaints, above, of mixing the fuel for 2 strokes - if you find it difficult I think you have bigger issues.

My complaint might be that 4t simply do not seem designed for the Marine environment, lots of mixing of stainless and aluminium with the inevitable corrosion - they then become impossible to service and are scrapped. The 4t small Suzuki 2hp has a mild steel coverplate over the valves - it corrodes. 4t might be environmentally friendly for emissions but the numbers that must be scrapped must negate that advantage - maybe I'm unlucky.

I note Geems comment on grunt in a wind and chop - I'd just get a bigger 2t as the 4t will be difficult to manhandle and store on passage (we would not hang it with the dinghy on the davits).

The question might be answered can you buy both? do you actually have a choice.

Jonathan

 

[geem]

In less developed or isolated parts of the world 2t are de rigour and parts and servicing easy. The 2 stroke will be lighter and easier to lift from dinghy to the mothership. I'm not sure of the regular complaints, above, of mixing the fuel for 2 strokes - if you find it difficult I think you have bigger issues.

My complaint might be that 4t simply do not seem designed for the Marine environment, lots of mixing of stainless and aluminium with the inevitable corrosion - they then become impossible to service and are scrapped. The 4t small Suzuki 2hp has a mild steel coverplate over the valves - it corrodes. 4t might be environmentally friendly for emissions but the numbers that must be scrapped must negate that advantage - maybe I'm unlucky.

I note Geems comment on grunt in a wind and chop - I'd just get a bigger 2t as the 4t will be difficult to manhandle and store on passage (we would not hang it with the dinghy on the davits).

The question might be answered can you buy both? do you actually have a choice.

Jonathan

You can buy 4 strokes in the French islands and both 4 stroke and 2 strokes in St M. Very few buy 4 strokes. You see lots of US boats with large 4 strokes as that's all they can buy in the US. I had the choice and I bought a Yamaha Enduro 15hp @ stroke in 2016. It gets used every day. Very reliable engine. I have also had in the past Tohatsu 9.8hp strokes. Another very reliable engine and surprisingly fuel efficient.

 

[Kelpie]

I changed my 2.2 2-stroke Suzuki for a 2.5 4-stroke and the new one seemed to have a lot more shove. I think that if you just want a tender-pusher and not a planer you will be quite happy with it. Although not perfect in all ways, the 4-stroke ran smoother without the faff of adding oil, and was easier to carry.

I'm interested to hear that you saw noticeably more power with the new engine. Of course you went from 2.2 to 2.5hp.

I'm taking a pretty elderly engine which is theoretically 3.5hp and switching to a new 2.5hp... I'd like to think I'll see a slight increase in power but it's probably wishful thinking. Does anybody know how outboards age? Do they lose a bit of power over the years?

 

[Kelpie]

Re the comments about weight, I'm pretty much specifically comparing my current Mercury 2.5hp with a Suzuki 2.5hp 4t. Both should be about 12-13kg.
I appreciate there is a huge weight difference once you start looking at bigger outboards.