Cummins Vs Volvo

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DREAMERTR

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Hello forum members and supporters. I have been benefiting as a quiet reader for while and time has come for me to request kindly some support :)

So, I need to decide between a 2002 Prestige 46 with VP TAMD75EDC and 2005 model with CUMMINS QSC 8.3. Both about 1000 hrs and service records available. I believe that both engines models have good reputation, no major issues for long years if looked after (kind of same with my wife).

Not sure what's the technology advances for Cummins as it was introduced later to replace TAMD75. Speed differences are small so is it just the consumption? I couldn't find consumption figures for cruise speed as well. Any experiences, knowledge on technology difference and realistic consumption figures at cruise speeds?

As boat needs to be transferred long distance, someone adviced me to cruise at 8-9 and I would get much more distance. I thought at planning speeds, consumption would be better following the adviced cruise speed. What is true here?
 
Can’t comment on the Cummins and whilst the Volvos are good motors you might want to read this thread

On your question about cruising speed a planing boat needs a lot of fuel to plane but if it stays at displacement speeds it will use a lot less and will do more miles per gallon. I am guessing but cruising at planing speeds it will do less than 1mpg.
 
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at 8 -9 knots you will get @ 2.5 maybe 3 mpg. It won't make much difference if you use one engine alternately or both together.
Planing at 20 kns+ 0.8 ish mpg
Engine make won't make a material difference. Sea state, load, how clean the hull and props are is more significant. If you need to move the boat a long way (600 - 1000 miles). Look into putting it on a lorry.
I would prefer the Cummins engines too.
 
Great to learn that I can save 65% to 70% on 8-9 knots vs cruise spreeds like 20-22 knots/hr.

I took quotations for transport but quite unrealistic level.

Choice with Cummins (same engine hrs, 3 yrs younger) is 25k eur more expensive at 200k eur but better equipped, better maintained, 9kw pagura generator installed 4 yrs ago vs much more hrs Onan 6Kw since 2002. And Garmin 6012/7012 newer navi tools vs Raymarine RV31, nicer teaks etc.
 
You will save massive serious money at 10 knots. I believe thekey is to not exceed the point when the turbos kick in. That usually for me is between 1000 and 1100 revs if my memory serves me well. The main problem is the state of the sea. If lumpy 10 knots is misery.
 
DREAMERTR said:
I took quotations for transport but quite unrealistic level.
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Remember that any sea route home is going to be the long way round, in addition to fuel you need to factor in marina overnight costs and expences.
If the weather is rubbish you could be there for days.
If any trip back involves an offshore journey you will undertaking it in a boat that you will be unfamiliar with and have no idea of its mechanical/ electronic reliability or how you and your crew will be under duress.
Accepting a sellers account of just how wonderful the boat is can be unwise.
Half way home is not the time to find out why most folks stick it on a lorry.
 
If going for the Cummins check the injector fuel pump model / part number - company I work for has a boat with QSC8.3 - water in fuel last year ended up having to replace injectors (no issue) and the fuel pump - big issue - there were only 2 pumps that I could find - both were in the USA and at big money
 
@Hooligan, I agree, would be total misery amd I may need to accelerate a bit more. I beleive stabililizers are available but not sure much to install a good one for a 46ft. Probably a project for later years if family keeps complaining.

@oldgit, well noted, very important indeed. If I go with Cummins, much less trip distance vs VP.

@rob, what number to look for? I think boat has water separator filters. Shouldn't this be the safety point? How can someone check the water in fuel or get rid of after winter?
 
DREAMERTR said:
@rob, what number to look for? I think boat has water separator filters. Shouldn't this be the safety point? How can someone check the water in fuel or get rid of after winter?
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WE have Racors and the main engine filter - but for whatever reason we had water go through the injectors and once that happens the pumps knackered. Our dead pump had the PN of 4954907 - This came up on the Cummins site as "Fuel Pump" and appeared to be the whole assembly.

It appeared to be made up of 3 sections - and by scrapping of the paint I found 2 new part numbers

The top section is 4902732 and comes up on the Cummins site as a fuel pump head

The main body that bolts onto the engine is 4954911 and comes up as fuel pump body

We tried another pump supplied from Merlin Diesels in the UK (V helpful guys - recommended). But although it was labelled forQSC8.3 - it just did not run correctly and we had to get the pump from the USA - something to do with the amount of fuel being put through - the pressure on both pumps were identical.

heigh ho - every day's a school day!
 
Looks as both brands have their own issues. Probably keeping the tanks on the full side at least is a precaution I heard is a good advice for water in the fuel problem.
 
Keeping the tanks full helps in the winter when the boat is idle to minimise condensation. However water may still get in via: - buying new fuel - it can have a bit of water in it. Best to buy fuel from places that are busy so it gets turned over regularly. Leaking fuel filler caps - fit new seals and grease the threads. Check the tank vent openings point down - sometimes they rotate upwards and catch rain. I have experienced all three.

See if the boat fuel tanks have an inspection sump/drain valves in the bottom. If so great - easy to check regularly for any bits of water that has got in and to get it out.
If not see if there are any inspection hatches or ports in the top you can put a tube down and suck up fuel/muck right from the bottom with a hand/electric pump periodically.
The normal fuel pick up pipe does not go right to the bottom they stop a few inches short to minimise the chances of the engine sucking up gunk.
If the boat has see-through inspection bowls on the main fuel filters that's great too. If not change the bowls to clear ones so you can see any evidence of water when you check regularly. Well worth it for peace of mind.
The fuel in the bowls should be absolutely crystal clear when you shine a torch through it. If it is hazy it has some water in suspension. Leave it for a few days and it will settle to the bottom of the bowl then drain it out see how much water comes out. It's not unusual to find a bit very occasionally and then (like tea spoon full amounts) as diesel is a bit hydroscopic and absorbs a bit of water.
What you don't want to see is water appearing in the primary filter bowl on a regular - everytime you use the boat basis. If that's happening get the tank flushed/cleaned and check the fillers etc.
It's not the end of the world if you get some water in your fuel tank as long as you keep a watchful eye on the situation and address it appropriately asap. I rarely fill my tanks completely to the brim so it can all slosh around and keep it fresh. Any water or gunk then gets sucked into the fuel filters where they do their job and warn you of any issue.
 
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