Mercury 60 EFI prop change?

[Happy Shopper]

Hi All,

To me this sounds like my problem maybe overall power output but would be nice to think I could improve things with a prop change for now!

I don't want to increase the top speed of my boat, with just myself on it it will just about make it to 30 knts but it's screaming at WOT as soon as you add another adult it immediatly you are looking at about 25 knts.

It would be nice to be cruising at around 25 knts without the engine screaming. Like my friend said you wouldnt drive your car around at 6000rpm constantly.

Am I asking too much? My boat is a ~5.5m Avon adventure (I think!)

The engine is only a few years old and I recall the previous owner changing the prop before when he put the new engine on. The boat did have a 75 suzuki previoulsy but that was stolen.

Would love to know your thoughts on this

Is there any measurements I can take of the current prop to get an idea of what I have?

[Starovich]

Should be stamped on the prop, sometimes just inside, or between the blades

[Happy Shopper]

Ok Great I'll try and pop out and have a look later.

[jyasaki]

Be aware it's often stamped on the part covered by the prop nut (or various spacers and washers that may be in there.)

Generally, you select a prop that gives you close to the max rpm (manufacturer spec) for the load you'll be running normally. This results in lower revs when loaded heavier, higher when loaded lighter.

You can, of course, prop up or down a bit if that suits you, but you may induce other problems doing so (over-revving or lugging depending on load and how much you decide to change your "normal" operating style.)

jky

[Downhilldai]

Is your RIB an Avon Searider 4.7?

[Locozodiac]

When engine runs max or near max wot rpm factory stated for that engine screamming is a natural thing, the difference if counting with a tach is that will know it's running safely at wot compared to ear tach in which you could be over revving engine without knowing it.

Check current prop size/diam, install a good quality induction tach, go for a wot spin you alone and lighly loaded rib and check achieved max wot numbers. Compare them to its factory stated min-max wot parameters. Will know if under or over propped with current prop and go from there selecting best prop for combo.

Could install a prop that gives full wot numbers with you alone and lightly loaded boat, bear in mind that when addding extra mates, rpm will drop accordingly. Nobody says you must run wot all the ttime, once correct prop is dialed for thet boat/engine combo can throttle to any position you like cruising at.

Happy Boating

[Happy Shopper]

Wow thanks for the replies all. I might get onto the yard that looks after my boat in the winter as they seem quite up to speed with it all!

I don't know if anyone can tell me the model of my rib from this photo? That's my other half's son on board!

[Downhilldai]

It looks like an Adventure 560. Your motor is quite under-powered for the boat, so 30kts is about as good as you'll get from it. I'd suggest you run a 12" or 13" pitch prop, depending on how heavily the boat is loaded.

[Downhilldai]

Originally Posted by Locozodiac

When engine runs max or near max wot rpm factory stated for that engine screamming is a natural thing, the difference if counting with a tach is that will know it's running safely at wot compared to ear tach in which you could be over revving engine without knowing it......

You won't over-rev it, as the motor has a rev-limiter that cuts in at 5900ish rpm.

[Happy Shopper]

I wonder what I'd get on a trade in on something slightly larger. Any ideas? I'd imagine the engine has probably done around 40 hours if that. ~2 years old.

[Happy Shopper]

Thanks again for all your help.

[Locozodiac]

Originally Posted by Downhilldai

You won't over-rev it, as the motor has a rev-limiter that cuts in at 5900ish rpm.

If engine cuts at 5900 ideal will be doing so near full open throtttle, not way before as you will have more wasted throttle that can't be utilized to take the max HP out of that engine.

Happy Boating

[jyasaki]

[QUOTE=Happy Shopper;622865]
It would be nice to be cruising at around 25 knts without the engine screaming. Like my friend said you wouldnt drive your car around at 6000rpm constantly.[quote]

Sorry, to go back to the original post...

No, but your car isn't designed for that. Your outboard (sort of) is, more than a car is, anyway.

jky

[henryfreston]

there should be an identification plate on the transom of the boat with its length and max hp rating.

[Happy Shopper]

This is the only ID plate I can see on it!

[PeterM]

I'd suggest you have 2002 Avon Adventure 560.

[Happy Shopper]

Great! Thank you!! Obvious really eh!

[henryfreston]

they have a max outboard rating of 115hp, so you are very under powered. THe speeds you are getting are probably about right and a well suited prop is not going to make that much of a difference with the lack of power.

You could either work out a deal with a dealer to do an exchange or sell the outboard separately and use the money to buy a bigger one. OR you could just sell the whole package and buy one that suits you better as I don't think it will be very cost effective switching the outboards (I may be wrong).

[matt h]

I had a 115 opti on my 560 and maxxed out got 42kts which i was chuffed with. that will give you an idea of what you can achieve with the right lump

[captnjack]

Originally Posted by Happy Shopper

I don't want to increase the top speed of my boat, with just myself on it it will just about make it to 30 knts but it's screaming at WOT as soon as you add another adult it immediatly you are looking at about 25 knts.

It would be nice to be cruising at around 25 knts without the engine screaming. Like my friend said you wouldnt drive your car around at 6000rpm constantly.

Am I asking too much? My boat is a ~5.5m Avon adventure (I think!)

The engine is only a few years old and I recall the previous owner changing the prop before when he put the new engine on. The boat did have a 75 suzuki previoulsy but that was stolen.

Would love to know your thoughts on this

Is there any measurements I can take of the current prop to get an idea of what I have?

You don't want to do this. The boat is underpowered, pretty plain and simple. With 75 ponies it was underpowered, 60 is just even worse.

If you want to cruise at 25hp, with a cruising rpm of about 38-4200 (typical), you need a bigger engine. Like 100hp minimum.

Swapping the prop will only make you over-propped.