PETE I've replied to your PM & email.
A 5hp will weigh 22kgs, so your getting double the power for nowhere near double the weight, only 4kgs or so, which in reality is what 4 litres of fuel would weigh. So if the 5hp has an integral tank and say 2 litres of fuel it will be almost the same! The Tohatsu (or any larger engine) will have an external tank so you can carry it separately, splitting the weight.
The Yam 6hp CMH model is 27 Kgs.
The 2008 Merc 9.9 4 stroke we have is 38 kgs. That's a lot for most to carry. You have to really want the benefits of 4 stroke (noise, ease of use, fuel efficiency) to go that route. I'd suggest it's not ideal as you have storage issues too then.
Your not limited to choosing between my two only though! Plenty out there to run with.
Other options include dolly wheels, trailering (although still need to remove motor to tow) or a pair of paddles
If your local to Plymouth your welcome to give it a try! You can try both the Tohatsu & the Mercury 4 Stroke to consider the comparisons. Bring the Yam and try that too.
Or use YouTube
Here's some examples. None are mine!
Quicksilver 3.1 + Yam 6hp 4 stroke - looks like 2 persons (1adult 1 unknown)
West Coast Compact 3.1 + Merc 9.9 4 stroke (same as mine) - 1 Adult
Avon 3.1m + Yam 9.9hp 2 Stroke (slightly heavier than my Tohatsu at 32kgs) + 1 Adult
3.1m + Tohatsu 9.8 (same engine as mine) + 1 adult
Zodiac 3.4 + Tohatsu 6hp 4 stroke + 1 Adult - seems to struggle
Hope that helps. Whichever way you go, enjoy but wear your kill cord! Or this could be you slooping out at 1min 06, if your that lucky...
Peter @ Boatsandoutboards4sale ~ email@example.com
~ 07930 421007