My first motor boat

[Dorset Dan]

I'm not sure that the £100-£150 per day in fuel is realistic - we have a Mag 350 MPi and so far only fueled up twice in 8 months - total cost c£550 from memory (this covers both fill ups, approx £275 each).

For that we have brought the boat back from Hamble Point to its berth in Poole, done two fulls days training (taking the boat out of Cobbs into Studland Bay and a lot of practice manouvering, etc). This year we have been out 6-7 times so far - at slow speeds out through Poole Harbour (10 knot limit for 1/2 hour each way which isn't great for fuel consumption) but then taken it up to higher speeds (25 knots) for a quick blast when out of the harbour for 1/2 hour a time, been round to Swanage or along Bournemouth Bay and usually end up anchoring at Studland or within the harbour. We still have about 1/2 tank of fuel......

Depends where you are berthing I suppose and we are lucky in Poole with some good places to explore close by without needing to travel tens of miles.

 

[aidanuk]

Thanks Dan, nice to read something a little less scary!

Most of my boating life has been out of Poole so Im familiar with that but ive been looking at Brixham as your right out to sea stright off the bat and can go to Torquay etc, not sure what the beeches are like round there / anchoring areas but if it dosnt work out we may get a swing mooring in poole.

The most important thing is a place to park and a reasonable easy way to get out to the mooring, Brixham is fairly small and is a working fishing port for security etc.

Very pleased to read your fuel report though Dan, has made me feel a lot better.

What size boat are you in?

 

[Dorset Dan]

Just found this from another site re Mercruiser Mag 350 MPi vs Mercruiser 5.0 MPi

"....But the remarkable comparisons we saw occurred at what we call "best cruise." This is the speed at which the boat is most fuel-efficient while on plane. In most cases this was at 3000 rpm. Here, the 5.0L engine moved the boats on average at 27.5 mph. The 350 MAG engine moved the boats, which were virtually the same average weight, at 27.6 mph -- just .1 mph faster!

At those speeds, the smaller engine got better fuel economy than the larger one by .05 miles per gallon -- 3.68 mpg for the 5.0L engine compared to 3.63 mpg for the 350 MAG engine on average. So the engine that is rated at 15% more horsepower at the top end, only loses about 1% in fuel efficiency in the mid range. This was the question that our readers wanted to know, and now we have the answer.

Essentially the 5.0L MPI MerCruiser engine and the 350 MAG MPI model are about the same in terms of both speed and fuel efficiency in the best cruise range."

I'm not sure what mpg a typical diesel engine of c300bhp would achieve but would be interesting to know.

 

[Dorset Dan]

What size boat are you in?

We have a Regal 2665 which is 26 feet but with the extended swim deck (most have this) it is just over 29 feet. We like it but as it is (I assume) built primarily with US trailer market in mind it has a narrow beam relative to length and I am already looking across at similar length boats (there is a Sealine SC29 opposite us at the marina and the wider beam seems to make it a lot more spacious despite being same length and paying the same berthing fees). We bought the best boat we could at the time though so need to save up some pennies for the next one before I start looking!

 

[lionelz]

Here a link to the boat that I have. The funny thing is the picture is of my boat but the write up is of a different one, The one they are describing is a petrol, the boat in the picture which is mine is diesel. Worth having a look at one, Got a good compliment on it just yesterday from someone in Gosport saying how nice the boat was (they have a very nice one) and how well the deck was laid out. Worth going to have a look at one if you can and well within your price range
http://rinker.apolloduck.com/feature.phtml?id=402681

 

[Monique]

Cure SWMBO of seasickness; get Sturgeron oral and suppository. IMO, sailboat motion is easier on queezy tummies than a Mobo....

GL

 

[TheOrs]

For your info: I have a 24ft sports cruiser (Fletcher 238) with the 350 Mag. If we go from the mooring at Laira (Plymouth) across to Cawsand & back it uses about 30-35 litres of fuel. This is about 1.5 miles down the river at idle and then about 3.5 miles across the Sound at cruising speed (about 25 knots) x2. When I bought the boat we brought it back from Torquay to Plymouth via Salcombe. This was 62 miles and we used about 150 litres of fuel. The weather was force 3-4 (waves were coming over the front occasionally) and we were running at slow cruise (around 22 knots) with tabs and drive down most of the time.
I notice in your posts you seem concerned about top speed. This was one of the reasons I bought the Fletcher/350 Mag combo. With a clean bottom she'll do 40 knots. Unfortunately, after a couple of months sat in the water, she'll only do 30 knots! More importantly I hardly ever use W.O.T. It's just too expensive. I would happily trade 10% off top end for 10% more MPG.
I also have a little Arrowflyte that I used for skiing and intended to sell when I bought the larger boat. The big boat is no good for skiing; the wake is massive, the fuel cost would be huge. I think now I would have been better off buying something slow(er) and economical and planning to keep the little sportsboat for skiing, fun etc.
HTH

Disclaimer: All speeds/amounts etc are approximate & retrieved from my memory, which is notoriously leaky.

 

[aidanuk]

Dan :

Interesting comparison on the engines there.
It looks like you are on the same sort of path I am, get what you can first then upgrade later if you want / need.

lionelz :

Its certainly a contender.

Monique :

Interesting, I figured while on the plane there is less of a rocking motion thus lessening the effect, however maybe when stationery I can perhaps see where your coming from.

TheOrs :

Thanks, some interesting numbers, not too scary and the sort of distance I think ill be going.
As you say WOT would only be used very sparingly due to the fuel cost im sure, Ill set a budget for fuel PA and can split that between going faster short distances or slower and going further at various points over the year and see how we go.

To be honest on the skiing front I should correct that to "inflatables" im sure if towing it will really just be ringos etc for the kids, I doubt there are many 30ft boats that can pull my fat ass out of the water!

 

[ontheplane]

Just found this from another site re Mercruiser Mag 350 MPi vs Mercruiser 5.0 MPi

"....But the remarkable comparisons we saw occurred at what we call "best cruise." This is the speed at which the boat is most fuel-efficient while on plane. In most cases this was at 3000 rpm. Here, the 5.0L engine moved the boats on average at 27.5 mph. The 350 MAG engine moved the boats, which were virtually the same average weight, at 27.6 mph -- just .1 mph faster!

At those speeds, the smaller engine got better fuel economy than the larger one by .05 miles per gallon -- 3.68 mpg for the 5.0L engine compared to 3.63 mpg for the 350 MAG engine on average. So the engine that is rated at 15% more horsepower at the top end, only loses about 1% in fuel efficiency in the mid range. This was the question that our readers wanted to know, and now we have the answer.

Essentially the 5.0L MPI MerCruiser engine and the 350 MAG MPI model are about the same in terms of both speed and fuel efficiency in the best cruise range."

I'm not sure what mpg a typical diesel engine of c300bhp would achieve but would be interesting to know.

That's interesting - but raises one weird and massively important question.....

If both boats in the test were doing the same speed (we can ignore 0.1mph) at the same revs, then I assume they had the same prop, and same g/b ratio yes? - If so, then surely the more powerful engine will just over-rev at the top end, OR the 5.0 would fail to reach max revs? I say this, because what's the point in the more powerful engine if it only went the same speed??

I would expect the more powerful engine to be able to swing a higher pitch prop, so at the same revs (3300 in the example) I would expect the 5.0 to be doing (say) 27 mph and the 350 Magnum to be doing 29 mph (assuming the 5.0 was on a 19" pitch prop and the Magnum running a 21") ??????7

Am I missing a point here somewhere?

Does the Magnum run up to much higher revs to get the benefit of the greater power.