Merry Fisher 855

[Chamaerops]

Really surprised the twins are faster and more economical than the single which seems to defy accepted logic.

I got 38 knots out of her this morning on Southampton Water and I don't even believe I was at WOT.
Also prior to this on the way along the Solent from the Beaulieu River, wave height had already started building due to the increasing wind speed and where I would have been bouncing around in the 645 and lowering my speed, I was instead cruising comfortably at 20-25 knots with much more confidence - I am rather impressed by the 855 handling.

 

[rwoofer]

I got 38 knots out of her this morning on Southampton Water and I don't even believe I was at WOT.
Also prior to this on the way along the Solent from the Beaulieu River, wave height had already started building due to the increasing wind speed and where I would have been bouncing around in the 645 and lowering my speed, I was instead cruising comfortably at 20-25 knots with much more confidence - I am rather impressed by the 855 handling.

Congratulations Chamaerops, that sounds a proper step up!

The fact that twins perform so well validates that you made the right choice. However, I'm still curious why the twins with their extra weight and drag can outperform a single of the same power. Must be something particular to the 855 as in nearly every other boat I'm aware of, the opposite is true.

 

[Garold]

Congratulations Chamaerops, that sounds a proper step up!

The fact that twins perform so well validates that you made the right choice. However, I'm still curious why the twins with their extra weight and drag can outperform a single of the same power. Must be something particular to the 855 as in nearly every other boat I'm aware of, the opposite is true.

+1. I'm surprised too.

Interestingly, I made the same decision with our new Antares 8.80 and had the twin engine version 'in spite' of what I believed would be some extra cost in fuel consumption, servicing, and top end speed.

I just wanted the reliance of having twins for safety and felt that any disadvantages of the twin engines would be an acceptable price to pay.

However, with your experience of the top end and the early fuel consumption info, perhaps there is little lost with having twin 150hp rather than single 300hp.

Garold

 

[rustybarge]

+1. I'm surprised too.

Interestingly, I made the same decision with our new Antares 8.80 and had the twin engine version 'in spite' of what I believed would be some extra cost in fuel consumption, servicing, and top end speed.

I just wanted the reliance of having twins for safety and felt that any disadvantages of the twin engines would be an acceptable price to pay.

However, with your experience of the top end and the early fuel consumption info, perhaps there is little lost with having twin 150hp rather than single 300hp.

Garold

Its a well known fact that twin diesels are as economical as a single in most boats over 30'.

so maybe the latest OB's with their super fuel economy ECU and electronic injection are able to match the diesel engine performance of twins in a smaller and lighter boat like the MF 855?

 

[dan from bhg]

Sounds like about 2mpg, compared to about 3-4 mpg on the 645. Really surprised the twins are faster and more economical than the single which seems to defy accepted logic. Why do you think that is?

I'm not quite sure. From the boats I've tested I've managed 34 knots with a single F300 and 38 knots with twin F300, so there is a noticeable difference. Maximum fuel consumption is higher with the twins, around 115 litres per hour with the twins vs. 101 litres per hour with the single (from my own experience). However, when cruising, there about the same, 40 litres per hour with the single and 45 litres per hour with the twins (at 25 knots). Again, these are from memory and tested a good few months apart, both boats with a very light load.

Remember the weights of the twins is considerably greater, twin Yamaha F150s are 446kg, plus the additional weight of the extra rigging and prop (long control cables and a big stainless prop do weigh a fair bit) whereas the single Yamaha F300 comes in at just 258kg. (bigger displacement than the Suzuki DF300 by the way, and much lighter too!!) This will make a difference, seeing as this extra weight is hanging off the back of the boat.

By the way, here's a video I made with the Yamaha F300 fitted, she goes pretty well: https://www.youtube.com/watch?v=fzgcx3bCVOY&feature=youtu.be

 

[dan from bhg]

I got 38 knots out of her this morning on Southampton Water and I don't even believe I was at WOT.
Also prior to this on the way along the Solent from the Beaulieu River, wave height had already started building due to the increasing wind speed and where I would have been bouncing around in the 645 and lowering my speed, I was instead cruising comfortably at 20-25 knots with much more confidence - I am rather impressed by the 855 handling.

We fit a larger prop than the size that Jeanneau recommend. The prop Jeanneau use is too small really, and you end up cruising far to high in the rev range and hitting the rev limiter at maximum speed. With the prop we use it hits max speed at 5900 RPM, sometimes 6000 RPM if it's trimmed right up, rather than shooting right up to 6000 RPM and sitting on the limiter right away. It does mean that our boats go a little faster than the Jeanneau recorded figures. And that MF855 of yours certainly isn't slow in getting onto the plane, it shoots up there!

 

[Chamaerops]

A wake video from our first outing on the new MF855.
http://youtu.be/exyolIRSUT4

 

[Bubblegtt]

Looking good there and I hope that you really enjoy your new boat.

Unfortunately mine is under propped. I went for the option of paying a little more and having stainless steel props, as a Honda option. I can't remember exactly, but the dealer told me that they were slightly smaller in diameter than the standard props. I can rev right round to 6,500 if I don't throttle back and this no doubt hurts the fuel consumption!

 

[Chamaerops]

These are my props which look very pretty and based on performance seem to be doing the job.

 

[dan from bhg]

Looking good there and I hope that you really enjoy your new boat.

Unfortunately mine is under propped. I went for the option of paying a little more and having stainless steel props, as a Honda option. I can't remember exactly, but the dealer told me that they were slightly smaller in diameter than the standard props. I can rev right round to 6,500 if I don't throttle back and this no doubt hurts the fuel consumption!

Let me know what size they are. Diameter and pitch.

 

[dan from bhg]

These are my props which look very pretty and based on performance seem to be doing the job.
View attachment 46880

Looking good! Those props are an absolute fortune to buy separately. Eye watering! Included as standard on a twin engine installation though

 

[webby]

Out of interest, what speed reading are you all using when quoting figures? GPS or Log? What tide and sea conditions? Seems to me you can't get an accurate comparison unless two boats side by side! I have seen 37knts (LOG) on my 300 single but not complete WOT as sea conditions (I was scared!) didn't allow. Lets have a drag race! Who's offering to pay for the fuel?

 

[Chamaerops]

My speed readings come straight off the GPS. I fulfilled one ambition today, by travelling up Southampton Water at the same speed as the Redjet. It would be very interesting to compare the twin 150hp vs 300hp in a direct comparison and I would happily pay for my own fuel

 

[dan from bhg]

Maybe when you venture on your trip to the West Country then Alan.

Perhaps I'll charter a RIB down there and be the official adjudicator!

 

[Bubblegtt]

Let me know what size they are. Diameter and pitch.

Heard back from Andy @ Morgan Marine and they fitted 14.5 inch x 15 pitch. Honda don't make stainless props in the same size as the standard 15.25 x 15 alloy.

It was my choice to go stainless and I paid the extra, even though they warned me that they were smaller in diameter. Honda do make a 14.5 x 17 in stainless, but I don't like the thought of buying another pair of props at those prices!!

Andy was talking to the Yamaha guy and he said that they fit 15.25 x 15 stainless on the 855 with twin 150's. Andy also mentioned that it may be possible to raise, or lower (can't remember which) the engines on the transom to increase the top speed.

I'm not hugely bothered about top speed, but it would be nice to cruise at lower revs and use less fuel

 

[dan from bhg]

Heard back from Andy @ Morgan Marine and they fitted 14.5 inch x 15 pitch. Honda don't make stainless props in the same size as the standard 15.25 x 15 alloy.

It was my choice to go stainless and I paid the extra, even though they warned me that they were smaller in diameter. Honda do make a 14.5 x 17 in stainless, but I don't like the thought of buying another pair of props at those prices!!

Andy was talking to the Yamaha guy and he said that they fit 15.25 x 15 stainless on the 855 with twin 150's. Andy also mentioned that it may be possible to raise, or lower (can't remember which) the engines on the transom to increase the top speed.

I'm not hugely bothered about top speed, but it would be nice to cruise at lower revs and use less fuel

I don't think the diameter will have much of an impact. That's more to do with blade flex differences between stainless and aluminium on out of the hole acceleration. If you're trying to reduce revs, and therefore fuel consumption at cruising speed, you need to increase your pitch. I always supply 17" pitch props on the 855, unless I know the boat is going to be fully loaded most off the time. In reality, most owners use the boat with four people max most of the time and the 17" pitch is perfect. You can see that webby and camaerops (both are my customers running 17" props, as are all my 855 customers) are obtaining good top speeds, but aren't struggling to get onto the plane. It's a much better suited pitch size IMO.

Raising the engines will increase top speed slightly, yes. But you also run the risk of increased cavitation in turns.

It would be interesting to compare speeds at certain revs between a boat running 15" props and 17". We tend to use our own experience and knowledge when selecting props at BHG Marine, rather than manufacturer recommendations.

 

[dan from bhg]

Looking good there and I hope that you really enjoy your new boat.

Unfortunately mine is under propped. I went for the option of paying a little more and having stainless steel props, as a Honda option. I can't remember exactly, but the dealer told me that they were slightly smaller in diameter than the standard props. I can rev right round to 6,500 if I don't throttle back and this no doubt hurts the fuel consumption!

I will also refer you to this: http://marine.honda.com/outboards/motor-detail/BF135-150 Note the maximum RPM in the specs, 5,000 to 6,000 RPM. I wouldn't want to be running it at 6,500 RPM, presumably that's sat on the rev limiter.

Just double checked what I fit, it's the 14 1/2 x 17" SDS polished stainless steel Yamaha props as standard. However, it's worth noting that the Yamaha and Honda final drive ratio might be different, so it might not be an exactly fair comparison, but it sounds like your is over-revving.

If you can save say 10 litres per hour at cruising speed, at marina prices, over the course of a year, it would be worth spending the money on bigger props to save in the long run. That is unless you plan on fully loading the boat on each outing.

 

[Nick_H]

Heard back from Andy @ Morgan Marine and they fitted 14.5 inch x 15 pitch. Honda don't make stainless props in the same size as the standard 15.25 x 15 alloy.

It was my choice to go stainless and I paid the extra, even though they warned me that they were smaller in diameter. Honda do make a 14.5 x 17 in stainless, but I don't like the thought of buying another pair of props at those prices!!

Andy was talking to the Yamaha guy and he said that they fit 15.25 x 15 stainless on the 855 with twin 150's. Andy also mentioned that it may be possible to raise, or lower (can't remember which) the engines on the transom to increase the top speed.

I'm not hugely bothered about top speed, but it would be nice to cruise at lower revs and use less fuel

Did you buy the boat and outboards as a package from the same dealer? If so, then I think the dealer should take some responsibility if the boat is under-propped, as seems to be the case, assuming you didn't override their advice. As an example they may be able to find a lightly used pair of the right size stainless props through the Honda dealer network, and swap them for yours.

When I bought a 300hp outboard recently, the supplying dealer allowed me to sea trial different props to select the right pitch to ensure I achieved best performance from the boat.

Raising the outboard may increase speed a bit, but if you're already on the rev limiter then it wont solve the problem, and increases the chance of prop ventilation.

 

[dan from bhg]

Did you buy the boat and outboards as a package from the same dealer? If so, then I think the dealer should take some responsibility if the boat is under-propped, as seems to be the case, assuming you didn't override their advice. As an example they may be able to find a lightly used pair of the right size stainless props through the Honda dealer network, and swap them for yours.

When I bought a 300hp outboard recently, the supplying dealer allowed me to sea trial different props to select the right pitch to ensure I achieved best performance from the boat.

Yes, I didn’t want to speak for the other dealer, but this is how we operate. If we’re not 100% sure on prop size, I let the customer sea trial the boat, and then give them the opportunity to exchange them if they’re not right. But then again, we hold huge stocks of Yamaha parts, so putting them into stock isn’t a big deal for us. Some dealers probably wouldn’t want an odd sized left handed stainless steel prop in stock. The other consideration is that the polished stainless steel props look very second hand very quickly, unless they’re cleaned thoroughly after each use, so we only offer this exchange within a very tight timeframe.

 

[Beyondhelp]

The props can be re-worked. You could pitch them up an inch, but by the sounds of this they require more than that. Lifting the engines is good if you can do so. Apart from the top speed it reduces drag and will get better efficiency. Sometimes doing this alone will require an inch in prop.