Which New Diesel

[Hallbergp28]

Hi All,

Does anyone know if there ia a formula/rule of thumb for the engine capacity that would be best suited to a given boat. I own a 1964 Hallberg Pacific 28 which currently has the roiginal Albin 10HP Petrol. I want to re-engine but am unsure as to how big I can go. Is the limitation engine dimension or what ?

Any information appreciated

 

[Peterduck]

I presume that you will replace with one of the plethora of small diesels which are now available. I also assume from the "28" in your boat's name that it is 28 ft long. The displacement is more useful as a guide to engine size, and there is nothing rigid about selection criteria even then. If, for example your boat displaces 5 tons, a 10hp Yanmar would probably be underpowered, 15hp may be about right, and 20 hp would be a little overpowering. There was a time when 1 hp per ton of displacement was considered de rigeur, but this figure has crept up over the years. Diesels give less actual power than petrol engines, but there is a greater reliability and safety. Space in the engine compartment also unfluences which engine you will choose, as does price. You will be able to get engine manufacturers' brochures which give the external dimensions of their engines. I have just installed a 40 hp Kubota in my own 10 ton ketch. They are marketed in the UK as a Nanni or a Beta in the marinised form. I find that it starts immediately, every time. Prefer an engine which has fresh water cooling and a heat exchanger, as this extends the life of the engine enormously. Raw water cooled engines rust out from the cooling jacket before they wear out.
Peter.

 

[Plum]

The modern rule of thumb is 4hp per ton displacement.

 

[kgi]

what you need to consider is brake mean effective power basically any engine only gives its rated HP at max revs, therefore it makes sense to get an engine that will drive the boat at its economical revs. i am not very good at explaining this maybe some one else could explain what i am trying to say!!!!!!! ( a20 hp engine at cruising rpm only puts out approx 12 hp)... hey that was a rush of rubbish to the brain!!!!!!!!

 

[Mirelle]

4hp/ton

Yes....

Mirelle, 9t displacement, began life with a 7.5hp Kelvin, which was replaced in 1967 with a 16hp Volvo.....which I keep meaning to replace, probably with a 29hp Nanni (Kubota) but the old one keeps chugging along and I am too mean to throw it out until it finally dies! But you are certainly right - we are notably and sometimes (eg Dutch canals) embarrassingly underpowered compared to more modern or more recently re-engined boats.

 

[Twister_Ken]

One very important consideration is actual physical fit. If the new engine needs new bearers, and/or a new prop and shaft, and/or new controls, and/or new exhaust runs, and/or new intake and hose positions for cooling water, and/or new hatches to get to service points, etc, the total cost of the changeover will grow very quickly (or if this DIY a weekend project will last half a season).

So consider very carefully not just the power of the new unit, but how you're going to get it in there, connected up.