prop talk

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jekyl

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I rarely see how fast she'll go but having HAD (I hope) some motor probs fixed, the mechanic and i took Tanami out for a blast today.
With just 2 of us and 100 gals of fuel my 200hpdi's got 5200-300 rpm.
They are 17 inch pitch. and give very good holeshot which i am willing to sacrafice.
I don't really care about holeshot or top speed . However cruising revs and efficiency is very important as most trips are a minimum of 2 hours out and 2 hours back at 28knots.
Any suggestions from those who have gone thru this exercise?
 
I'm thinking 200 hpdi's with 17" pitch props, should wind up a lot higher than 5200-5300. Are you sure that the throttles are going full-stop, and is the bottom clean of any growth? Engines trimmed up for max speed? Just seems low to me for those engines/prop combo.

Just as a comparison, my heavier Sailfish with 4 stroke 225's & 19" props, clean bottom (painted), turn up 5400 or even a litttle better. I will be dropping to 17" 3 blade or 16" 4 blade to get the numbers I want.

Maybe someone else with a 265 can chime in.
 
You might talk to the guy at Prop Doc - www.PropMd.com, or Andy at SIM - www.shipyardisland.com - for some input.

You didn't say what props you have, whether they're black stainless yamahas, or what.

I can't help you directly, but have done a ton of research on props and have read everything I can find. There are some good reports on the performance props that Merc puts out, like the Enertia. And for the heavy blue water boats (like yours) there have been good things said for the Yamaha Salt Water Series props.

Hole shot and top speed are good indicators of what you'll get at cruise. A good hole-shot will help in climbing waves and for low-speed planing. Top rpm just tells you if you're over or under propped for your HP and weight. Some props might give you an extra mph or two, higher will usually be at the expense of hole-shot but can bump cruise a bit too. I'm not sure sure that doesn't come at the expense of some fuel cost though. Some say a certain prop 'bites' better, if they have a certain cut or shape, and thin blades. That's the idea behind the Enertia prop.

But yeah, for best cruise, there are various options that can bump your efficiency a bit, so they say. There are always a few guys that just rave about some prop they run, but I often wonder if it's really that different than just a standard setup.
 
Thanks for ideas, These props are yamaha stainless, painted black 15" x 17 pitch .
Without getting them off I just measured from the centre of the hub to the furtherest point on the blade x 2.
I am not unhappy with the performance overall just don't want to be loosing any efficiency.
As i was not heavily laden I expected a better topend for those motors.
 
Captn. Bill I believe the four strokes are able to rev considerably higher .
Tanami is on a trailer and has no bottom paint so that's not an issue.
 
You really can't compare the RPM's of a HPDI and a FXXX, they have different gear ratios in the lower unit. At 6000 RPM a F225 is spinning the prop as fast as a HPDI is at 5580 (5400 is equal to 5000). There are a lot of variables for props, cup makes a difference on the load the engine sees but also lets the prop bitte harder. I would think you should be able to get over 5300 with the light load.
 
The yamaha black stainless props have a very good reputation, although they are not considered high-performance. But then, I'm not sure that a "high peformance" prop would make much difference with your application.

Here's a link to the yamaha prop options for the HPDI200:
http://www.yamaha-motor.com/outboard/ac ... all/1.aspx

I'll bet Andy at SIM would recommend the RELIANCE for your setup. If you went witht the 14-1/4X17 you would pick up a couple of hundred RPM at WOT for the smaller diameter, and because it's a little more efficient prop you might see a couple of MPH at cruise for a given rpm and a couple at WOT.

The Reliance is not as aggressive at the Saltwater Series. The latter has a more pronounced cup and in fact, are not even recommended for the F150. The HPDI200 would probably push them though, but if you went with the 15-1/2X17 you would probably lose a hundred or so rpms. I'm not sure that would accomplish what you want.

I tried a Reliance on mine and it was just a shade better than my 15-1/4X15 for the F150, but they are expensive ($600 ea) so it wasn't worth it to me. They are beautiful props though.

Write or call Andy and talk to him about what you have and what you're after and see what he suggests. He gets a ton of feed back because of his forum thread on THT.

If you could get a dealer over there to loan you a pair of Reliance props they would be worth a try. Most dealers will do that. But shipping from the states just to try them could get expensive. Plus, you have to justify any gains for the cost of new props. A pair of good stainless props is going to run from $900 to $1200 (USD) plus shipping.

I'm pretty sure Prop Doc will loan you props too, or maybe there's a prop dealer over there that will bring some props out and let you try them. Another option is to borrow a pair from another boat owner, that's pretty painless, but you have to find a generous boating buddy that would be willing to do that for you.

BTW, you mentioned measuring them without pulling them - make sure you pull them at least a couple of times a year and grease the splines, shaft and thrust washers so they don't get corroded and stuck. That's a real PITA.

Let us know what you end up going with. I'm real interested as I'll probaby end up with the exact same setup.
 
Thanks for the info guys. The props have been pulled when serviced 6 months ago.I'm pretty fanatical about the servicing being done.
I will try another speed trial when weather conditions are a little calmer.
It was blowing 20 knots the other day and i wasn't able to find much calm water.Also probably didn't have motors trimmed out as much as I would in better conditions.
I wouldn't normally do a long trip in that situation either.
She is an awesome boat. I do think the four strokes would be better for my application, as we do lots of trolling . However the changeover cost makes it not worth considering at this point.
 
I know this is very late but now that my motors are running really well I came back to this question.
One thing I noticed in the Yamaha test data is that the motors are on #1 hole. Is that first at the top of the 4 holes or first at the bottom?
Mine is second from the top and the cav plates look fairly level with the bottom of the transom( although that is hard to judge on 22deg )
I don't think I can go much higher. If I have the motors trimmed out for cruise as I come of the plane they usually cavitate a little until I remember to trim them in a bit.
Also I have a "bone to pick" with Yamaha in not showing figures at 4500 and 3500 rpm which is very often the working cruise range of most 2 strokes in a variety of conditions.
 
There will be a sweet spot, a combo of speed and revs that is most efficient for you boat but it is difficult to easily identify it. The starting point is the Yamaha test reports for you boat and motor combo.
If you were to change props and get say a tenth or two increase in fuel economy, you would need to run a lot of hours to get a return on the prop investment.
The cheapest ways to improve economy are:
Reduce weight ( don't fill up the gas if you don't have to; Don't fill up the fresh water tank; Remove unnecessary gear. approx 25 gals of water or fuel is equivalent to another average passenger)
Keep a clean hull ( and smooth. Rough paint creates drag)
Make sure the props are tuned and motors are run in sync
Adjust your trim for efficiency.
And of course, keep motors in tune. You may benefit from more frequent plug changes.
 
Where are your cavatation plates when you are on plane and trimmed properly? If they're burried and you can't even see them, they're too low. In theory if they should be about even with the water. Slightly under will use have a little more drag but will have more bite if it gets snotty. If they're high'n'dry, drop them.
 
Another good point Grog, I forgot to mention that the tops of the plates are not clear of the water. I would say they are just under at cruise.

Has anyone else noticed a slight cavitation only as they just come off the plane if the motors are still trimmed out for cruise?
 
Capt Bill said:
I'm thinking 200 hpdi's with 17" pitch props, should wind up a lot higher than 5200-5300. Are you sure that the throttles are going full-stop, and is the bottom clean of any growth? Engines trimmed up for max speed? Just seems low to me for those engines/prop combo.

Just as a comparison, my heavier Sailfish with 4 stroke 225's & 19" props, clean bottom (painted), turn up 5400 or even a litttle better. I will be dropping to 17" 3 blade or 16" 4 blade to get the numbers I want.

Maybe someone else with a 265 can chime in.
Click to expand...

Capt Bill,
you only get 5400rpms? likely you and i are both running Yami SS SWS 19" props. Hull is clean and no bottom paint on mine (from your avatar yours doesn't look painted either). i think i get 56-5800 rpms on the F225's. not sure why you would go down in pitch as that would further drop your rpm's. if i get a change in feb or else this summer, i plan to test a set of new props (merc Mirage Plus SS 19", similar to SWS) and see which one is better and keep the other pair as spare.
 
bc282 said:
Capt Bill said:
I'm thinking 200 hpdi's with 17" pitch props, should wind up a lot higher than 5200-5300. Are you sure that the throttles are going full-stop, and is the bottom clean of any growth? Engines trimmed up for max speed? Just seems low to me for those engines/prop combo.

Just as a comparison, my heavier Sailfish with 4 stroke 225's & 19" props, clean bottom (painted), turn up 5400 or even a litttle better. I will be dropping to 17" 3 blade or 16" 4 blade to get the numbers I want.

Maybe someone else with a 265 can chime in.
Click to expand...

Capt Bill,
you only get 5400rpms? likely you and i are both running Yami SS SWS 19" props. Hull is clean and no bottom paint on mine (from your avatar yours doesn't look painted either). i think i get 56-5800 rpms on the F225's. not sure why you would go down in pitch as that would further drop your rpm's. if i get a change in feb or else this summer, i plan to test a set of new props (merc Mirage Plus SS 19", similar to SWS) and see which one is better and keep the other pair as spare.
Click to expand...

Yes, I'm maxed out at 5400-5500, but the bottom is painted. Pic in avatar is from the day I bought the boat. Re about going down in pitch; reducing pitch and/or diameter by one inch will increase rpm by about 200. So if I go from a 19" SWS, which I have now, to a 17", my rpm's should go up to about 6k. Yes?
 
Capt Bill said:
bc282 said:
Capt Bill said:
I'm thinking 200 hpdi's with 17" pitch props, should wind up a lot higher than 5200-5300. Are you sure that the throttles are going full-stop, and is the bottom clean of any growth? Engines trimmed up for max speed? Just seems low to me for those engines/prop combo.

Just as a comparison, my heavier Sailfish with 4 stroke 225's & 19" props, clean bottom (painted), turn up 5400 or even a litttle better. I will be dropping to 17" 3 blade or 16" 4 blade to get the numbers I want.

Maybe someone else with a 265 can chime in.
Click to expand...

Capt Bill,
you only get 5400rpms? likely you and i are both running Yami SS SWS 19" props. Hull is clean and no bottom paint on mine (from your avatar yours doesn't look painted either). i think i get 56-5800 rpms on the F225's. not sure why you would go down in pitch as that would further drop your rpm's. if i get a change in feb or else this summer, i plan to test a set of new props (merc Mirage Plus SS 19", similar to SWS) and see which one is better and keep the other pair as spare.
Click to expand...

Yes, I'm maxed out at 5400-5500, but the bottom is painted. Pic in avatar is from the day I bought the boat. Re about going down in pitch; reducing pitch and/or diameter by one inch will increase rpm by about 200. So if I go from a 19" SWS, which I have now, to a 17", my rpm's should go up to about 6k. Yes?
Click to expand...

Generally, decreasing prop diameter will increase rpm, but i wouldn't recommend it. Usually the only reason to decrease prop diameter is when you go from a 3 blade to a 4 blade prop. If you drop down in size and keep the 3 blade design, then your performance will suffer. such as slower hole shot, higher min. planning speed, and general loss in lower speed performance. Also generally, increasing prop pitch will increase engine rpm. as a guideline, 2" pitch changes will move about 200 rpm. Has the boat with those engines always performed at WOT at 5400 rpm? i'd first see why the F225's with 19" SWS isn't turning the proper rpm's before investing in expensive set of props. you've probably seen on yami's performance reports that the 282 with F225's running SWS 19" wheels turn 5800 rpm at WOT. the yami report is pretty close to dead on with me.
 
real world is 1" is 100-150 rpm
going from 3 to 4 drops about 100-150 also

the HPDI a should turn 6000, limiters are set at 6150

you also need to trim it out also!

most gradys run 17" or 19" props
 
Your engine should be reaching 5500rpm max, and with only 100gal you are propped wrong. If you achieved that at full load with full fuel and a heavy load of gear and 4-5 onboard I'd say your ok. To see if you are propped right you need full fuel, you cannot test it any other way. Run it hard out, and both with and against the current, not the wind, the current. This is the proper way to test a boat and get accuaret results and eliminate many other variables. An average of the two is what you should use, too many guys test boats or use numbers from running only one direction, which will only show half your usage in reality. Why you want to prop a boat to handle a heavy load is for the days you do run out with full gear and it might get nasty out, this provides the safety of knowing you have the power to get over the hump of larger waves, or to ride with them depending on conditions. The way you are propped now, if you ever encountered really nasty seas and were loaded with full fuel and a heavy load of gear you would have issues getting onto plane, not something you want when the seas kick up. If you are turning about 200-300rpm off max with a full load, you should be able to get to max rpm at half load which is likely 1/2 of your usage for most boaters. By having a engine propped this way, you should be near you most efficient set up, you can always tweak it a little. As for size I am uncertain, I do not have the HPDI's on that boat but this is how you want to properly check for the right prop.
You may want to look into mercury propellers, many have had great results from them and for the same price have gotten even better fuel numbers from them. Another benefit is for a while, not sure if they still are offering it, Mercury dealers offered a program where you put a down payment down to test a propeller until you find the right one and your down payment goes to your prop purchase in the end unless you damage them. This is really the best way to do it if you can find a dealer who honors this program. If I were to change props, that is the route I woudl go. I've hear good things from those who switches to Mercury props from Yamaha.
 
I'm confused .... currently I get excellent holeshot even fully loaded she jumps onto the plane.
However the lack of revs at the top end makes me think I may be losing some efficiency at cruise revs.
In car terms it's as tho' I am stuck in 4th gear and I'm looking for 5th for highway cruising.......
Tom she handles rough weather on the nose, fully loaded, well, we can drop back to 3,500 and she'll keep up on plane at about 20 - 23 knots.
Surely my props are slightly over pitched and I need something a little less that will turn easier and give me a better cruise?
 
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