Originally Posted by Pete7
Alan / John this is quite interesting, are you therefore saying that modern injection outboards are a cost effective alternative when compared to the complexity and cost of bulding inboards and jets, assuming a commerical operator can get the tax back on petrol ?
In terms of power to weight ratio, performance and space the OBs now do win. The cost per mile works out about the same provided duty and VATrebate is in place. Other factors such as ease of replacement, leg or jet wear etc also come into play.
Critically the resale value of OBs after say 12 months use is very high compared to an IB.
The major drawback is obtaining fuel supply and it is for this reason that a number of our customers have set on IBs.
One f the difficulties with IBs is the limited number of suitable units on the market suitable for a production RIB. Yanmar and Volvo hold the lead at present but with units of 315hp a single installation is barely adequate to power a 10m (noting that if they were OBs twin 150hp would be adequate). Thus twin installations are required which on say a 3m overall beam gives very little space to play with. Worse is the cost of a twin IB of say £40k as oposed to £16k for twin OBs !.
I am no great fan of OBs and they have their share of downsides (we need to lug 250 galls on a busy day !!) but after many years of playing the cards they have won in our view.
The reference to the RNLI and jets I believe is for shallow water/estuary work and is one of the applications including close quarters handling when the jet will win every time.