100Hp Yamaha on Merry Fisher 645 - Opinions welcome please

[Newman]

Evening all

I would appreciate opinions on having a Yamaha 100HP outboard engine on a Jenneau Merry Fisher 645, having noticed that most 645's seem to have 115HP's fitted.

Not being in a mad rush to get anywhere fast, but still wanting a bit of power there should it be needed, is the 100HP considered man enough ?

Comments will be most welcome

Thanks in advance

 

[rustybarge]

Evening all

I would appreciate opinions on having a Yamaha 100HP outboard engine on a Jenneau Merry Fisher 645, having noticed that most 645's seem to have 115HP's fitted.

Not being in a mad rush to get anywhere fast, but still wanting a bit of power there should it be needed, is the 100HP considered man enough ?

Comments will be most welcome

Thanks in advance

the Mf 625 was very happy on 90hp, but I think the lastest models have put on 200kg in weight.

 

[Spi D]

Jeanneau states 115 hp so by the rule of thumb ('not less than 75-80% of max. recommended') a 100 hp should do fine if propped right.

Weight is a key factor so depending on your intended use, you might need all you can get (budget). The boat alone is 1345 kg so if you add engine, fuel, water, crew and gear in the range of 500 kg, I'd expect it to do some 24-27 knots with 100 hp. Keeping weight down will compensate for less hp. Time to plane will depend on weight distribution and use of engine powertrim.

 

[Sheppy]

Just out of interest, what's the reason for looking at a 100 and not a 115, surely not just cost?
It's worth considering future saleability too, if you put on something that others think is slightly under powered, then some buyers might be put off, especially if it's lower than the recommended size.
Personally though I think you'd be fine.

 

[sea-commander]

You can expect ca. 26-27 knots topspeed with the 115hp.
In an MBM test vmax was 26 knots @ 5.400rpm with a Suzuki 115.
About 18 knots / 4.000 rpm is quite a good cruising speed.
I'm sure that the 100hp will bring the boat on the plane as well, losing only a few knots. But that also means, that the engine has to rev higher for cruising speed.
To be honest, I'd go for the 115 Yamaha.

BTW: Great choice, the MF645 is a very nice boat.
Chris

 

[Newman]

Many sincere thanks for answers so far received. They are all much appreciated and most helpful.

I am looking to buy a Merry Fisher 645 and among those currently for sale is a very nice, well equipped 645 Legend BUT with a 100HP Yamaha fitted. Hence my question and interest.

Having looked at various boats of similar nature and size I am 'hooked' on the 645 for my all round intended use

Thanks again

 

[Matt341]

There is currently a 2011 MF645 Legend for sale on the same marina leg as us, this also has a Yamaha 100hp (maybe the same boat that you are looking at?). I would think that speed difference between the 115 & 100 will be marginal if you are looking at cruising speeds but max speeds may be a little better with the 115, if you are ever going to get upto max speeds. Our boat has a stated max speed of 30+ knots but I have never found the need to push the engine hard enough to reach this. You may also require a little higher rev's to get on the plane with the 100 v the 115.

There is another 645 in the marina which has a 90hp so it seems that the engine choice at purchase was fairly flexible.

 

[Nautibusiness]

Hi Newman

I am a Jeanneau dealer and (former) owner of two separate Jeanneau.

Unless it is really cheap, but one with a 115Hp as you will always be left wanting with anything smaller.
The 115Hp will give the upper side of mid 20s, but will cruise happily at 18 to 20 knots.
The 100Hp will be working much harder to achieve the same results and so the ride will be less pleasant (re noisy and harder work) and fuel costs probably higher in anything other than calm conditions.

Why anyone would have fitted a 100Hp from new is beyond me, but it would need to be much cheaper indeed.

The old 625 was originally supplied with a 70 or a 90. The 70 was a waste of time. The 90 just about managed, but was left considerably wanting when alongside the 115.
The same will be apparent on the new larger 645.
Get one with the biggest engine rated to the hull. It will also seriously help in the future when you do finally sell up, but will be much more enjoyable at all speeds during use.