Best outboard for a Merry Fisher 625

[installer2]

I am planning to buy a Merry Fisher 625 next Spring. From my research it seems the best engine would be a 115hp EFI outboard with stainless steel prop - either Yamaha or Suzuki. Am I on the right lines, and if so roughly what average overall fuel consumption (litres per mile) should I budget for?
Thanks
Hugh

 

[Oscar24]

Hello,
I have a Merry Fisher 645 with a 115hp Suzuki 4 stroke. A nice combination which give a cruising speed of around 18kts and tops out at 22kts.
I've never actually worked out the fuel economy (at 6kts it hardly uses anything) but i can have a very nice day out with 40ltrs on board.
That's a combination of running at 6kts and 18kts. At WOT i.e 22kts you will chew through the fuel

The 625 is pretty much the same boat, I would recommend getting the biggest engine option available for it (not sure if thats 90, 100 or 115
The 645 has a max engine of 115.
Re make of engine, im very happy with the Suzuki but if getting a 115 don't get a stainless prop. My mechanic told me the gearbox on the 115 can get damaged if a stainless prop hits the bottom. He recommended the standard aluminium prop but pitched correctly for what you want.
With engines, all modern outboards seem pretty reliable tbh. I would pick something which the local dealer can service.

 

[Hot Property]

Buy a Honda, mine was bullet proof. If you are so inclined, you can service it yourself and retain your warranty coverage.

I think they are the only manufacturer that allows this......

 

[installer2]

Hello,
I have a Merry Fisher 645 with a 115hp Suzuki 4 stroke. A nice combination which give a cruising speed of around 18kts and tops out at 22kts.
I've never actually worked out the fuel economy (at 6kts it hardly uses anything) but i can have a very nice day out with 40ltrs on board.
That's a combination of running at 6kts and 18kts. At WOT i.e 22kts you will chew through the fuel

The 625 is pretty much the same boat, I would recommend getting the biggest engine option available for it (not sure if thats 90, 100 or 115
The 645 has a max engine of 115.
Re make of engine, im very happy with the Suzuki but if getting a 115 don't get a stainless prop. My mechanic told me the gearbox on the 115 can get damaged if a stainless prop hits the bottom. He recommended the standard aluminium prop but pitched correctly for what you want.
With engines, all modern outboards seem pretty reliable tbh. I would pick something which the local dealer can service.

Hi Oscar
Thanks for that. I'm only a rookie but wouldn't 6kts mean displacement speed and therefore be heavier on the fuel?

 

[installer2]

Buy a Honda, mine was bullet proof. If you are so inclined, you can service it yourself and retain your warranty coverage.

I think they are the only manufacturer that allows this......

Thanks for your message. haven't seen Honda recommended before, its mainly Yamaha and Suzuki that people strongly favour on MF 625's. Servicing an outboard for me is mission impossible, whenever I've been under the bonnet of a car its not started again!

 

[Hot Property]

Thanks for your message. haven't seen Honda recommended before, its mainly Yamaha and Suzuki that people strongly favour on MF 625's. Servicing an outboard for me is mission impossible, whenever I've been under the bonnet of a car its not started again!

Ah, in that case you should probably just choose one that has a service agent near to where you keep the boat......

 

[Hot Property]

Hi Oscar
Thanks for that. I'm only a rookie but wouldn't 6kts mean displacement speed and therefore be heavier on the fuel?

Displacement speed is the most economical for fuel use. Your boat will have what is know as its "Hull Speed" - worked out by 1.34 x √LWL .

So if the hull is say 16ft on the water line, the hull speed is 1.34 x 4 = 5.36 knots.

Up to this speed the boat just pushes the water out of the way. Once you try to go faster the boat starts to climb a hill of water which uses significantly more fuel. So if you tried to do 10 knots you will probably double (or more) your fuel consumption.

Once you get over this "hump" of water you are then on the plane. Probably around 16/18 knots range. this is the next most economical speed for any boat.

After that, the fuel/speed curve rises generally proportionally until you get to what is known as WOT - Wide Open Throttle.

At this point the engine is consuming maximum fuel - not many people run at WOT, only to blow the cobwebs out really - don't be frightened to use WOT occasionally, as it tests all the engines systems and they are designed to rev at high speeds.

Fuel cost is not your most important costs - berthing will probably trump that by a long way!! Good luck.

 

[[178529]]

Hi Oscar
Thanks for that. I'm only a rookie but wouldn't 6kts mean displacement speed and therefore be heavier on the fuel?

below about 3/4 of max hull speed at displacement stage is very economical. As the bow wave builds and the boat has to climb it as it get to the 'hump', or max displacement speed, economy gets exponentially worse. as the boat breaks free of the bow wve and gets onto the plane then that again becomes economical. Economy then goes down in a straightline with speed beyond that.

So there are two speeds that are good for economy. about 3/4 hull speed, which would probably be the 7 - 7 knot mark and then just up on the plane, around 13/14 ish.

 

[Bouba]

The difference between modern four strokes is marginal but I always had a Honda, it’s reputation for reliability is rightfully earned

 

[YellowPeril]

I have a 2016 MF605 with a Suzuki 115. Whilst a little smaller than the 625, it may be heavier.

From memory:
At idle it will use approx. 0.7 litre per hour once warm.
At ~2000rpm / 6 knots, it uses between 2.5 and 5 litres per hour (depending on the current).
The sweet spot is at 4200rpm which allows us to cruise at ~19 knots. This uses approx. 18 litres per hour (let’s say 1 litre per mile).
At WOT we can just about hit 30 knots in flat conditions, but fuel usage exceeds 46 litres per hour (so 1.5+ litres per mile).

I have no idea which propeller is best – I have the standard aluminium one. Having hit a rock and properly bent it, I was glad it was aluminium as the replacement cost was significantly cheaper.

The consensus seems to be that all modern outboards are equally reliable, so manufacturer is often best chosen by having a good local service agent.
If buying used, condition/price/overall package may be the decider.

Hope this helps. Good luck with your search.

 

[pumpsmynads]

I have a similarly sized boat. A 605 pilothouse with a mercury 115ct. I use the attached litres per hour to work out fuel economy. I know from experience that 1500rpm is about 4/5 knots. 2500rpm about 7/8. And so on etc.. So I know as a rough guide what I’m using. I can basically pootle around for 1 gallon per hour. 4100rpm is cruising speed circa 18 knots. WOT is 30 knots.

 

[Fishtigua]

If you want to save money, put a sail up. If you want go out and enjoy yourself, get at big Merc. All the smaller ones are made by Tohatsu but the big ones are very well designed and built. Never seen a duff one.

 

[Farmer Piles]

I have a 5.9m Yamarin HT with a 115 Yamaha, a great combination. 35kts flat out, cruise at 18-20kts and does about 6 mpg at that speed. 6 kts is marginally less fuel efficient than 18 kts on my boat.
I wouldn't go for any less power than that for your boat, more would be better than less. Get 6 people in ours and you can really feel the difference, she still flies along but engine working much harder. Check the rating for your hull but I would think 130-150hp.

 

[Rafnar UK Limited]

I am planning to buy a Merry Fisher 625 next Spring. From my research it seems the best engine would be a 115hp EFI outboard with stainless steel prop - either Yamaha or Suzuki. Am I on the right lines, and if so roughly what average overall fuel consumption (litres per mile) should I budget for?
Thanks
Hugh

Hiya,
I'm a former Jeanneau dealer and was with the brand throughout the (new) sales life of the 625.
By far the most preferable engine is the 115 with most on the used market being Suzuki as we sold them as standard with Jeanneau throughout the production run.

You'll find a few fitted with 90Hp, but they tend to struggle a bit in any kind of seaway and tide and therefore actually end up using more fuel than the 115 overall.
That said, in equal / neutral conditions expect the 90Hp to deliver about 26 knots and the 115 about 28 knots at wide open throttle.

Ideal cruising rpm is 4,000 with the standard aluminium prop.
This will deliver somewhere between 18 and 20 knots with the 115 and burn about 1.25lpnm at those revs.

Boats from 2003 should be checked thoroughly.
At Ostroda there were two production lines and one line built superb boats the other seemed to have an "off few days" with the bonding between the inner tray lining and the outer hull being missed / not done correctly on a number of boats.
There was a factory recall that was handled very well and I would like to think that every effected boat was properly fixed, but I would want "mine" checked if I was buying. It was only 2003 boats and didn't effect them all.

Good luck with your search
Tom

 

[Jamie Dundee]

Hiya,
I'm a former Jeanneau dealer and was with the brand throughout the (new) sales life of the 625.
By far the most preferable engine is the 115 with most on the used market being Suzuki as we sold them as standard with Jeanneau throughout the production run.

You'll find a few fitted with 90Hp, but they tend to struggle a bit in any kind of seaway and tide and therefore actually end up using more fuel than the 115 overall.
That said, in equal / neutral conditions expect the 90Hp to deliver about 26 knots and the 115 about 28 knots at wide open throttle.

Ideal cruising rpm is 4,000 with the standard aluminium prop.
This will deliver somewhere between 18 and 20 knots with the 115 and burn about 1.25lpnm at those revs.

Boats from 2003 should be checked thoroughly.
At Ostroda there were two production lines and one line built superb boats the other seemed to have an "off few days" with the bonding between the inner tray lining and the outer hull being missed / not done correctly on a number of boats.
There was a factory recall that was handled very well and I would like to think that every effected boat was properly fixed, but I would want "mine" checked if I was buying. It was only 2003 boats and didn't effect them all.

Good luck with your search
Tom

Now that’s a damned fine reply

 

[QBhoy]

Hi. Without doubt mercury are miles ahead of the rest right now. No one is close to them since they changed the way they make the most recent engines. In particular the new 115 2.1l is an amazing machine. It’s lighter than the old 2 stroke and has been tested at way more than the claimed 115hp on the badge. It even outperformed the 125 optimax on the same boat revently.
make sure it’s the CT model. I have one and I’m constantly amazed by its performance. I’ve it on a 19ft fletcher cuddy. She will see 43-45 mph gps with either a tempest or enertia prop on her. Just amazing from only a 115hp. Cruising she will see around 1.5-1.7 miles per litre at mid 20’s. Staggering numbers really. No other 115 will compare to it. That’s a fact.

 

[Joze Velnar]

Hi. Without doubt mercury are miles ahead of the rest right now. No one is close to them since they changed the way they make the most recent engines. In particular the new 115 2.1l is an amazing machine. It’s lighter than the old 2 stroke and has been tested at way more than the claimed 115hp on the badge. It even outperformed the 125 optimax on the same boat revently.
make sure it’s the CT model. I have one and I’m constantly amazed by its performance. I’ve it on a 19ft fletcher cuddy. She will see 43-45 mph gps with either a tempest or enertia prop on her. Just amazing from only a 115hp. Cruising she will see around 1.5-1.7 miles per litre at mid 20’s. Staggering numbers really. No other 115 will compare to it. That’s a fact.

Hello,
what propeller are you using on the 19ft fletcher cuddy + Mercury 115 CT? I have a Merry Fisher 605 + Mercury 115 CT, very heavy (approx. 2200 kg (engine, gasoline, people, equipment...). Which propeller do you recommend? Thank you in advance for your reply.

 

[QBhoy]

Hello,
what propeller are you using on the 19ft fletcher cuddy + Mercury 115 CT? I have a Merry Fisher 605 + Mercury 115 CT, very heavy (approx. 2200 kg (engine, gasoline, people, equipment...). Which propeller do you recommend? Thank you in advance for your reply.

Hi. My boat is much lighter than yours for sure. I think she is around 1000kgs dry. Likely about a max of 1200-1300 kgs with fuel and 3 of us aboard perhaps.
Anyway, I have tried loads of props on her so far. I mostly run a 19” tempest plus on her, for all round ability. Some data below from 3 or 4 of the props I’ve ran most.

19” tempest plus
43 mph gps any day of the week with hood up or down no probs. 44 mph gps if light and hood down. Around 6050-6150 on the rpm limiter in the right conditions.

20” enertia
44 mph gps most days and 45 mph on a good day often achieved. Around 6000 rpm or just over.

19” laser 2 43mph gps very easily but on the limiter just as easy at 6150 rpm

The enertia is the quickest prop I’ve tried for sure, but not terribly happy slow planing
The laser 2 is quick but not good on fuel in comparison to the other 2 and much higher rpm for same speed cruising or going slow.
The tempest plus is honestly incredible. It keeps the boat on plane at low rpm for the pitch. Significantly better on fuel than any other prop I’ve tried. So efficient cruising and going slow. Almost acts like an inch more pitch for rpm, but still acts like the pitch for acceleration. Cruising I can regularly see 1.7 miles per litre. That’s pretty much anywhere between 21-27 mph. Always around the 1.7.
I’d imagine that the tempest would suit your boat too. Likely you’ll need less pitch, but definitely it’s true that these engines are at their best if the prop is pitched to allow you to see right up the top end of the rpms. You want to be able to see around the 6000 or even a little more, to get the best from it. What pitch and prop are you running now ?

 

[Joze Velnar]

Hello,



so far, I have used the classic Mercury Marine 115 engine (Four stroke), with a 1:2.07 gear box and a prop. “Black Max D=13.75 / P=15''”. Maximum speed 26 kt at 5900 rpm. The boat barely came on plane.
Cruise 21-22 kt at approx. 5000 rpm. Cruise 21-22 kt at approx. 5000 rpm.