Fuel guzzling Honda

Gaz22

Gaz22

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Hi, My new boat a hardy pilot has a honda bf 75hp bolted on the back, when sailing the boat back from the dealers we used 52lts fuel to cover 23 miles at 22 Knots it was good weather and RPM was reduced to 5000 is this normal fuel usage or do l have a problem? /forums/images/graemlins/confused.gif

The boat does not have trim tabs fitted, does anyone have a similar boat to confirm how much fuel it may or should use or advice on how reduce trips to the local filling station.
 
5000 rpm???

That sounds INCREDIBLY high rpm for cruising.

I don't know what max rpm for this engine is - but assuming that it's 6000 rpm I wouldn't be expecting to cruise any higher than 4000 rpm ideally.

What length / weight is the boat - I would have thought at those revs the boat would be going a lot faster than 22kts as well... Is the prop the right spec?
 
It's a semi-displacement boat so don't expect it will do much more than that at full throttle. Basically I think he was travelling at well above an economical cruising speed. I would reckon that that would be nearer to 15kts and he'd be using perhaps a quarter of the fuel.
 
max RPMs for the engine is 5400, if we chug along at 4000revs all we get is 9-10 knots with her bow in the air, we need to give her a good burst of throttle to get on the plane, l am looking at fitting trim tabs hoping this will get her onto the plane quicker and then reduce throttle to save fuel, fingers crossed.

never thought about the prop being the wrong spec, thought the engine would have been matched to suit the boat when fitted, will have to ask questions on that one!

thanks G

PS the boat is 20 ft and the newer version the planeing hull.
 
That is about right. The boat is quite heavy and semi displacement. The 75hp is really the smallest engine you could put on it for any form of performance. You will have to work her hard and means poor fuel consumption. I take it you have a 4 stroke engine? I can get about 2.8mpg out of a 90hp (ETEC 2 stroke) on a 20ft centre console boat.

BTW, with the hull trim tabs will not help. What you need is a smaller prop and a 'dole fin' which will help pop her out. Cost abot £50 from swindelrys.

Cheers

Paul /forums/images/graemlins/smile.gif
 
Hi

I tend to agree with the others. But as an interesting and quite similar comparison I have a Merry Fisher 625 with a Suzuki DF90hp, so similar size boat although being french... probably lighter and a bit more power. The boat gets on the plane around 3800rpm and I cruise at between 4000 to 4300rpm around 19 to 22 knots. 5400rpm is around its maximum and with a clean bottom will run at 26knots. But the Suzuki DF90 is a detuned 115hp so does have a lot of low down torque. My fuel consumption is around 20 liters an hour at cruising speed, but I have just fitted a fuel flow meter so will be finding out exactly this season and will keep you posted!

A couple of things to mention.

1.Weight distribution, make sure you have not stored everything aft! Get some equipment in the bow locker, or forward bunk!

2. Trim, get the engine trimmed right in to aid getting on the plane at lower speeds, but trim out slightly once boat on the plane.

3. Find out what pitch prop is fitted, it might be you need to go up a few pitches, or perhaps down... but this is where you need some professional advice as prop's are expensive and a total waste if the change makes performance worse! As a reference my prop is 17" pitch. Find some other Hardy Pilot owners and ask for comparisons!

4. Trim tabs will certainly help, I would recommend the traditional type will help this size of boat (http://www.bennetttrimtabs.com/techhome.php) rather than the slide down Volvo Penta QL Trim Tab type.

At the end of the day the Hardy Pilot is a great boat and with a 75hp will plane but perhaps you might consider a more leisurely semi-displacement cruising speed with the occasional blast to clear the cobwebs. I would just say, if you can handle the fuel cost the Honda engine (as with all Honda's) will be fairly happy at higher rev's and are very good engines.
 
You know all those those odd sized props that come up for sale on the boaty websites or Ebay ? /forums/images/graemlins/smile.gif
People who have bought several flavours of replacement props before going back to whatever they started out with.
Worth a word with the boat builder,existing engine/prop combination on your boat was not bunged on at random,but possibly an unholy compromise twixt speed and economy.
However if a natty collection of props at £300 quid a pop is your thing...........
 
As others have said the Hardy Pilot is a semi-displacement and not as efficient at speed as a proper planing hull. Again as others have said 2mpg isn't bad at that speed for a Hardy Pilot. Also as others have said, don't bother with trim tabs but a doelfin would help improve economy and 'planing' as it lifts up the back of the boat.

If you want true planing performance then maybe a Merry Fisher / Arvor etc might be a better option.
 
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