merryfisher 585

medline

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hi all
i have just bought a merry fisher 585 with a suzuki df70 on the back, its kitted out for the weekends full fuel tank etc. it has a standard 17 pitch prop.
with 4 on board we are hitting only 3000 revs and digging in at the stern and not getting on the plane with out moving every one forward. with two on board it hits 5000 revs and gets on the plane slowly.
has anyone else got this boat and have they tried a 15 pitch prop? other advice welcomed
 

Geoffs

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I suspect that 70hp is a bit light for a 585, which is a heavyish boat for it's size anyway.

Does the outboard have any hydraulic trim, if so, is it trimmed right down when getting on plane.

Don't know about prop pitch, but if getting 5000 with two up, probably OK. I think you'll need more hp, if you want carry 4 regularly.
 

landlockedpirate

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Hi, your engine was working very hard. Speak to your local dealer but I think you would need to go down to a 15" prop when lightly loaded and even a 13" with 4 aboard.

Remember your boat is not a sportsboat so even with the correct prop its never going to leap on the plane. At over 1000kg dry its heavy for a 70hp. (A similar sized sports boat could have over 200hp)

An outboard hydrafoil will also help to get you over the hump.

Nice looking boat and welcome to the forum !

Mark
 

Steveu

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I agree with landlockedpirate
You don't rally want to change the engine unless it's really necessary so:
reduce prop pitch
fit outboard hydrofoil (cheap & easy)
trim engine right down when trying to get over the hump
send people forward
don't take so many people

If you experiment with these factors then you'll be away!
 

Davy_S

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It is worth checking how deep the cavitation plate is in the water, you can gain quite a bit of speed by raising the engine an inch, it should be level with the bottom of the hull, any more loses speed.
I am sure as others have said that a 17 inch pitch is too much, see if you can borrow a 15 inch pitch and give it a try, Am sure you will see an improvement.
good luck.
 

RobEllis

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My MF580 has a Mercury 75 with a 14in prop on it. It revs over 5000 with 3 on board and gets on the plane quite easily. It is a bit lighter than your 585 though.
 

medline

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thanks guys looks like the way to go may be a new prop, i do have her fully trimmed down and the engine should give me 5800 revs so i am guessing 15 inch is what i need anyway for 2 people on board. i was hoping that someone else had already changed theirs and could advise me to the last 1/2 inch, but then i am greedy!
 

RobEllis

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antiqueboy, I've tried to reply to your PM three times but nothing is showing on my Sent Messages. Just didn't want you to think I was ignoring you. /forums/images/graemlins/blush.gif
 

jhr

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Are you ticking the little box that says "Do you want to keep a copy of this message" when you compose your pm? If not, I'm guessing that antiqueboy has 3 messages from you.... /forums/images/graemlins/smile.gif
 

SnaxMuppet

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I had a Cap Camarat 625 with a DF140. Now I now that this is a different beast and it is well powered for the boat but I did play around with the props and had some interesting results.

It came with the standard 17" prop. The acceptable WOT for that engine is 5600-6200 and with the 17" it was at about 6200 and with that prop it just leapt onto the plane even with 4 onboard. However, we do a lot of low speed pottering and don't ski so it made sense to try out a coarser pitch prop so we got a 21".

It dropped the WOT to about 5600 so that was OK but it had 2 major effects... it was much more sluggish onto the plane... not so much with 2 people but more noticable with 4 people... and it noticably improved our fuel consumption at low speed (about 5kts).

One side effect I did notice on the last trip I did with her before we sold her was in rougher weather the fuel consumption was noticable higher! I put that down to having less acceleration up over the waves. The revs varied much more too in rougher weather as the engine went on and off load. The 17" prop was much better for rougher seas.

Finally, one other effect it had that I noticed was that at tickover it was faster through the water and so when berthing there was more into/out of gear to control speed whereas before I could just leave it in gear on tickover - now it was too fast!

Once I get a fuel flow sensor fitted to my new boat I am going to do some proper tests to determine the performance change between props. I now have a Merry Fisher 625 with a Suzuki DF115 but it takes the same props as the 140 and comes with a standard 19". I can then try out my 21" and see if there is any noticable difference.

I will post the results when I have them (probably a month or two yet tho' /forums/images/graemlins/smile.gif )
 

medline

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Arny i am hoping that dropping two sizes will mean the opposite that i will leap out of the water when i open her up, if only i can use the revs available, i am concerned that she is labouring like a car in 5th doing 30 going up hill,
RobEllis sorry for the delay in answering, many thanks for your reply i will be checking out diameters of the props.
 
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