Is it worth re-propping my 115 yammy 4 stroke?

[reel overtime]

I have a crusiecraft outsider 550 with a 115 yamaha four stroke pushing it.

It does 27-28 mile an hour at 5000rpm, if i sit on 3800rpm i get like 23 mile per hour. (and yes, i've just changed my gauges so they read in knots, i haven't been back out since)

Would re-propping give me better top end speed or any benefit?

i believe they make full torque at around 4300-4500 rpm, so if anything would i get a greater pitch prop to make it work harder as i've already passed the max torque range?

i might give the blokes a call at solas and see what they say.

Cheers!

Todd.

[gofishin]

Todd,
What revs do you get at WOT? This will be what Steve at SOLAS will ask/need to know. Your donk will have a max recommended rpm range, probably 5500-6000, and your motor should be able to easily achieve the upper end of this with your boat in the usual trim/loaded condition, some prefer with full fuel load too so that the motor is never labouring.

There will probably be many options of props to achieve this, choosing the right one to get the most out of it in the cruise range is the tricky part, but Steve will have a good idea what will work for your boat ;)
cheers

[black runner]

As gofish said,

You should be aiming to pull at least 5750 WOT otherwise you are bordering on overloading your motor if you can only just pull 5k. If so you will need to reduce the pitch not increase.

Cheers

[Nomad62]

Hi Todd,
Do you have any trouble getting on the plane as well.....i notice you have a foil on the motor.

Do give Steve a call at solas....he is a legend with propping, he has given me some great advice in the past. Selecting the right prop can turn problem boating right around.

Like the other guys say....get some accurate info ,revs,speed ,trim etc this will assist solas to select the right prop for you.

Cheers Nomad

[reel overtime]

yeah steve called today, he is concerned that the motor is sitting too low in the water and part of the reason i'm not getting the rpm. so first i'm going to look at where the foil sits in the water on the plane.

Wot is 5000 rpm, on a mill pond day 5200, thats with only 2 people on board and 100L of fuel, so she needs a little attention to get her up to scratch.

[Nomad62]

Yeah thats a good point....having the motor down to far will give poor performance. Even moving it up one hole can make a big difference.

Do you reckon the foil has made any difference to the boat?

I would think ideal revs would be between 5500 and 6000 WOT.

Nomad


yeah steve called today, he is concerned that the motor is sitting too low in the water and part of the reason i'm not getting the rpm. so first i'm going to look at where the foil sits in the water on the plane.

Wot is 5000 rpm, on a mill pond day 5200, thats with only 2 people on board and 100L of fuel, so she needs a little attention to get her up to scratch.

[Moonlighter]

Hi Todd

It definitely sounds like you need to address both the engine height and the pitch, but as Steve has probably told you, you have to get the engine height right first. As others have commented, its bad for your motor to be pulling such low revs - its like running a car in too high a gear all the time. Get the height and pitch right and the performance difference will be unbelievable - I found out the same thing myself!

Here's a link to a really good easy to follow article on the Verado members website that goes into the height issue quite clearly, and best of all includes some real life photos of how your cav plate should look when its at the right height.

http://www.veradoclub.com/smf/index.php?topic=137.0 (http://www.veradoclub.com/smf/index.php?topic=137.0)

Hope this helps.

ML

[Scalem]

I am just about to take delivery of a Brand spankin new 115 Yammy 4s, so I've Spoken to Solas about getting a non Yammy prop to acheive better performance thinking that I can always turn to that option if I find I want more performance on a 6M boat. They say the 4 blade ( not sure what pitch, probably a 15 or 17) will optimally keep the revs around the 6000RPM at WOT which is the designers specification for this motor. I have spoken to other 115 owners where one cruises on 5000 RPM and said it can go a lot further, but just makes a lot more noise for little extra gain with the original Yammie prop, so the fact you are at 5K WOT doesn't sound right to me.

Here's the point to consider though, as mentioned by the dealer - because my new motor will be under warranty, if I re prop with anything BUT a genuine Yammy and something goes wrong with the motor, I could find myself fighting to have a claim under warranty, depending on the nature of the failure. Not worth the hassel IMHO, look at engine heights etc B4 re-propping, especially if still under warranty.

Scalem

[reel overtime]

nomad 62, the foil makes a little bit of difference, mostly noticeable on the plane the ability to dramatically alter the trim which i like.

I'm not sure about warranty, the previous owner didn't say anything (i'll go round a see him about it actually) it is an 06 motor with 260 hours on it so it'd be out of warranty or not far from it anyway.

[Spaniard_King]

warranty wont be effected as long as the engine operates as per the manufaurers recommended RPM range.

Solas tend to reommend 4 blades on 4 strokes these days and really without justification. The problem with the 4 Blade is it takes decent chunk o horsepowe to drie the forth blade oer 4500 rpm (ie its over efficient ) so instead of runing a 16 or 17 pitch 3 blade your down to a 15 pitch 4 blade to try and get the rpm to meet them manufacturers specs. The downside to this is your always cruising at higher rpm with a 4 blade than what you would be with the 3 blade.

I did a lot of testing with Solas props in high load applications and we just couldn't get the performance out of the 4 blade in high rpm situations.

Get the engine height right its certainly a key indicator for good performance.

[black runner]

The answer to your question is yes.

With a 115hp yammie on the 550 (which may be about minimum recommended for that hull), dropping an inch or two in pitch will give you about the same speed numbers but at the right cruise, WOT rpm and better holeshot.

Cruising at 4000-4300 for 20+/-kts would be a good number with your combo and you would be in the torque range you quote for max fuel efficiency.

I don't believe you are going increase your speed numbers with the 115 yammie on the hull.

FNQ Cairns is a good one to get prop input from.

Cheers