Best prop for 18ft Searay and Merc 3L

[hardworking]

Hey all,

So we have recently purchases a SeaRay glass 18 footer with a 3L Merc Stern Drive and I am not sure the prop that is on it is the right one. I have the service record of when it was fitted, so I know it has been replaced from the original.

This prop is a 4 Blade, and from mostly what I have read it should be a 3 blade.

I am not looking for high speed. I am more looking for good pull for a skier or boarder, with some decent speed up high - Sort of an all rounder.

We were out in it last weekend and it was a struggle to get a couple of the guys out of the water, and with a 135 in the back, I thought it would have been easier.

Any tips are much welcomed.

Cheers
John

[Duckfish]

Probably a starting point would be a 18" pitch prop, four or three blade. My two bobs worth.
Duck

[MyWay]

try 3X14.8X19

[hardworking]

Lol. I don't want to start "trying" props. They are not cheap.


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[TheRealPoMo]

18 footer American with a 4 cyl is always gonna be a struggle...especially towing skiers . Talk to Solas but as has been mentioned on this forum - if you are getting max rpm at WOT then the prop is good.
The 4 blade was probably fitted to lift the rear and lower the plane speed. Probably cut 1 to 2 knots off as a trade off.
Wake boarding and ski boats have V8s in them.

[bigjimg]

Bang in your boat info and see what is recommended. Jim

https://www.mercurymarine.com/en-gb/au/propellers/selector/?utm_term=en-gb&utm_medium=us+&utm_source=Overlay_IP%3Dau&utm_campaign=Region+Redirection#/step-one

[hardworking]

Yeah I've done that but it's confused me more than I was. Lol.


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[scottar]

Unfortunately you are asking the one prop to do two things that are to a point, exclusive. Think of props as gears in a car. To "snap" a skier out easily you want a prop that is easy for your engine to get revs up from a standing start - 1st or maybe 2nd. To run at " a good speed" you need a taller ratio - 4th or 5th. Neither gear does the other job really well and ultimately you end up with third that does neither really well but is a compromise. With skiing, it is not uncommon for boats to require a second, lower pitch prop to enable them to do the job easily - even more so when they are not a dedicated, highly powered vessel.

A couple of things I would do - first, do a WOT run with your existing 4 blade to make sure it is reaching the specified WOT RPM for your engine. Not only will this establish whether your existing prop is suitable for a "non skiing" day out, it will also assist someone like Solas by establishing a baseline. Then as mentioned, deal with someone like Solas - a good company to deal with for propeller selection as not only do they have a heap of experience, they will keep swapping props provided you don't ding them, until you are happy.

[hardworking]

Thanks Scott. I have read some info in prop runs but not sure how to do it for my boat. I'm back on the water Saturday so if I can find out how, can do it then.


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[scottar]

Pretty easy - long straight run in flat water with the hammer down and trim the engine to get the best boat speed. Make a note of the highest RPM achieved and boat speed - preferably off a GPS rather than a speedo if you have one.

[hardworking]

Ok. So trim all the way down? Or adjust on the run?


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[scottar]

Would normally start with it all the way down and then trim up gradually a bit at a time. you will generally hear/see the revs pick up and the speed with it. If you trim too far, it will either "break out" or revs will go up but speed down.

[hardworking]

Ok cool. I guess I need to find out now what my boat should be doing at WOT. I will track that down.


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[Fed]

Got a serial number?

Probably find your motor at http://www.baylinerownersclub.org/index.php/forum/boc-library/3795-manual-downloads-and-good-reading-how-to-s?limitstart=0

If you need #10 it's around the net & I'll find it for you.

Mercury runs on serial numbers.

[robothefisho]

My go to props for lake boats pulling skiers are normally mercury high fives. Failing that a prop with vent holes is a must. Blindly guessing a 17 pitch high five would be the go.

[hardworking]

Thanks for the links Fred. I will grab the serial number shortly but it's a 2004 model.


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[hardworking]

Got a serial number?

Probably find your motor at http://www.baylinerownersclub.org/index.php/forum/boc-library/3795-manual-downloads-and-good-reading-how-to-s?limitstart=0

If you need #10 it's around the net & I'll find it for you.

Mercury runs on serial numbers.


Ok - I have my SN. It's OM685070

I have read through some material and WOT RPM should be between 4400 and 4800rpm.

So tomorrow I will do some testing on the lake and use my iPhone app to check speed and get back to you all.

Oh - and the current prop is a 4 blade 14x19RH Spitfire

Cheers
John

[MyWay]

Lol. I don't want to start "trying" props. They are not cheap.


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this is what is on sea ray sport with 3.o L and it is ok
from here u can ask Solas for size and tune your boat for your needs

solas will help you with all they got ton of knowledge and expiriance

[hardworking]

Thanks MyWay. I have sent them an email.

Cheers
John

[hardworking]

Spoke to Solas via email and they have recommended a new 14.25 19 inch 4 blade. Still discussing with them, but will let you know.

[scottar]

Did you find out the pitch on your existing 4 blade??

[hardworking]

According to the paperwork its a Spitfire 14x19RH

[scottar]

Just not sure how much you will pick up rev wise replacing a 19" with a 19". I assume they have recommended stainless so there may be some gain there. Did you specifically ask for a prop for skiing (doing deepwater starts) or for a general use prop?

[hardworking]

Yep! That's what I thought, but they stated that the prop I have is for an outboard and does not have a large blade area. They did recommend SS, but out of my budget for now.

[scottar]

Still seems strange - it is one of Mercury's suitable series when you run you details through the prop selector and if the prop they are going to fit has a larger blade area in theory it will be harder to turn - slower to accelerate. If you don't want to wait until you can afford a new one, and specifically want a prop for skiing as a second prop, I would keep an eye on Gumtree or Ebay for a 17" 4 blade or a 17" large blade 3 blade (usually get them for a few hundred), have a chat with a good Merc dealer to see what they recommend or better still, try and borrow a prop for a quick trial - not sure where you are and unfortunately all my stuff is BRP so it won't fit but there is sure to be a member with a prop or too to try or buy sitting in the shed.

[hardworking]

Thanks Scott. But my prop is 14 inch is it not?? 14x19... Isn't that a 14 inch with 19 pitch?


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[scottar]

Thanks Scott. But my prop is 14 inch is it not?? 14x19... Isn't that a 14 inch with 19 pitch?


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Sorry - those measurements were for pitch. Diameter of prop for a particular series of prop to suit a series of motor is generally set by the manufacturer. The only variable in the equation that the end user can typically choose within a prop series is the pitch. 4 blade props usually have a smaller diameter than 3 blade and certainly with the BRP stuff, a large blade area 3 blade has a bigger diameter than a "standard" 3 blade.

[hardworking]

Ahh - I get ya! Thanks!

I will be talking with them tomorrow and let you know what they say.