Pro's and cons of size of engine and boat.

[stainless welder]

Good day everyone.

I am looking at a buying a 2nd hand rib
for the purpose of scuba diving, and have come to fork in the road over these boats

7meter soft nose powered by a 225HP 4stroke

and the other is a 5.2 meter hard nose powered by a 80Hp 2 stroke

Can assume that the 200hp will drink fuel? Will the drag of the hull have an effect of consumption

effects of a 80Hp, slower to get onto the plan and not as reliable as a 4stroke.

what would happen if I where to change the 80hp for a more powerful engine and what considerations would I need to take account of?

[ptm]

Hi there.
I don’t dive, but assuming you will be ferrying other passengers with the required equipment, a rib of reasonable size like the 7 metre, with the extra power, would make more sense. You are more likely to get on the plane with less effort, therefore less drag. The smaller boat most likely won’t be rated much above 80hp anyway(maybe 100hp), so not much in the way of extra benefits. A four stroke engine can be quite economical, and you could always ask your buddies to contribute. What are the boats you are considering?

[fastasfox]

I do dive and I know how heavy tanks weight belts,bc's etc are so the more roomy bigger rib with 225hp on the back would make perfect sense and remember just because it has more power doesn't mean you have to use it...but four divers and their kit and I think you will be glad you went for......as Jeremy Clarkson would say "POWER"

[Matt]

Absolutely the 7m. If you get caught out in a bit of rough stuff and need to get home quickly, but safely, the 80 will be underpowered. I used to do rescue duty in a 5.0 with a 60 and 3 up with not much by way of extra kit, it was desperately underpowered if the conditions were nasty. The 225, assuming modernish, will be pretty frugal at cruising speeds, give you about a 40 knot max speed, but with the right prop, give you a good amount of load carrying ability too, while still making good progress.

[Wave Rider]

7m all day long