3.5hp vs 4hp outboard.

[wipe_out]

Hi. In the process of looking for a tender and outboard for the boat. On a previous boat we had a 2.7m tender and a 3.5hp outboard and with two people it was ok but the engine could never reach full power and I don’t think it was possible to get a lower pitch prop.

So I am thinking about a 4hp this time around and probably a 2.3-2.5m boat. I get that it will be about 7kg heavier but wondering if the larger capacity engine will have better torque and power delivery?

I have no experience of the 4hp so looking for thoughts and opinions.
Thanks.

 

[lw395]

The right prop will make far more difference than 0.5HP extra.
Alternate props are available for some outboards.
I had a 4HP which would be quite fast if you could use a wave to get on the plane, but a Malta had better low speed thrust.
Some fourstrokes don't have great low speed torque IMHO.

A 2HP is only a bit slower over all, and SWMBO can start it consistently, so I'm happy with that. YMMV.

 

[Star-Lord]

There will be zero difference with two people. With one person you may be able to get on the plane if you have not eaten too many pies! The great thing about 3.5hp is it is still relatively easy to manhandle. A Suzuki 2.5hp is even easier to throw around and if not planning why go bigger? They are so light.

A 4hp (4 stroke) is the same weight as a 5hp and 6hp engine so if you want that weight may as well go 6hp. One up 6hp is not bad Most people will need a crane or boom or halyard to lift 4/5/6hp on and off dinghy. 3.5hp is doable if you are fairly strong or young. Suzuki 2.5hp was my favourite single cylinder 4 stroke outboard. Very easy to lift up and down with no lifting equipment required.

If using single cylinder outboards 2.5hp up to 6hp Sea Foam 1 Pack (16 Ounce) Extreme Marine & Rv SF-16 Seafoam Liquid 16 Fl Oz: Amazon.co.uk: Business, Industry & Science this fuel additive will be very useful.

 

[steve66]

There will be zero difference with two people. With one person you may be able to get on the plane if you have not eaten too many pies! The great thing about 3.5hp is it is still relatively easy to manhandle. A Suzuki 2.5hp is even easier to throw around and if not planning why go bigger? They are so light.

A 4hp (4 stroke) is the same weight as a 5hp and 6hp engine so if you want that weight may as well go 6hp. One up 6hp is not bad Most people will need a crane or boom or halyard to lift 4/5/6hp on and off dinghy. 3.5hp is doable if you are fairly strong or young. Suzuki 2.5hp was my favourite single cylinder 4 stroke outboard. Very easy to lift up and down with no gear.

If using single cylinder outboards 2.5hp up to 6hp Sea Foam 1 Pack (16 Ounce) Extreme Marine & Rv SF-16 Seafoam Liquid 16 Fl Oz: Amazon.co.uk: Business, Industry & Science this fuel additive will be very useful.

TBH if you follow manufacturers guidelines and drain your carburettor you will never ever need to use, clean or replace your carb

 

[Star-Lord]

TBH if you follow manufacturers guidelines and drain your carburettor you will never ever need to use, clean or replace your carb

Do you mean run the engine dry? Or take the cowling off and manually drain every last drop (something I have never tried) Is it even possible to do so? I had a Honda generator where you could take the cover off and use a screwdriver to manually drain the carb but the carb still blocked up.

It has been my observation that every single cylinder outboard has its own character.

I religiously drain my 10hp 2 cylinder outboard (discount fuel line and run it dry ) and it has never gummed up and is amazing (i also use a small inline filter in the fuel line). I still use Seafoam to keep petrol fresh when you need to stock up with a Jerry can or two.

I had a 2.5hp Suzuki that never failed to start till I read you should drain the carb. When I started draining the carb it would never start. I had a 3.5hp that never failed to start - if the carb was drained - and if the engine was never tilted up while on the dinghy... but after a season it would need a service because it was very hard to start. Seafoam usually solved all those problems.

 

[steve66]

I mean drain every drop from the carburettor, drains are built into carb bowls specifically for this. Cant see how when you drained your honda generators carburettor it still used to get blocked.
your absolutely correct...every outboard has its own character. 2 strokes and older 4 stroke models will run on poorer fuel.....new 4 strokes will not run on older fuel