Raker alternatives

[petterg]

Hi guys

I'm looking for an alternative to Raker. One that is somewhat less aggressive. I feel that the Raker uses much energy to fight gravity with the sternlift. My stern lifts it self easily, but the bow does need help to rise. I think a bit less trailing edge cupping to the Raker would do. My engine is mounted high (stepped transom), so I need the prop to be suitable for near-surface operation. Also, I prefer good fuel economy at cruising speed over acceleration, hence I don't want (nor need) any ventilation holes.

One reseller recommend Ballistic. From what I read online lots of users of the Ballistic are happy with its performance. All the happy users seems to have one thing i common: Prop running deep. The users of the Ballistic in near surface operations seems to be unhappy. As my boat likes the engine high, there's a high risk I'll end up in the group of unhappy users.

Another reseller say Rapture. To my understanding the Rapture is similar to the Ballistic but heavier. Then I assume it doesn't love high mounted engines either.

A third reseller say they don't have any suitable props.

So what are my options? Some of the options I see is:
1) Modify a Raker. Give it less trailing edge cupping and plug the vent holes. Will such work destroy its near-surface capabilities?
2) Modify a Ballistic. Give it better grip in near surface conditions. How would that be done? Is it a matter of adding trailing edge cupping?
3) Find another prop.

When it comes to finding other props I've been looking at PowerTech. PowerTech catalog list some interesting props. There is the high rake / light cupped TSO3. It sounds like what I'm looking for, except that an old catalog I found say the TSO3 is for running deep. Another interesting prop is the NRS3 which they say is "more aggressive than RED, less aggressive than PTR". About RED3 they say it's similar to Rapture and Ballistic. The description of PTR3 sounds much like Raker. Hence the NRS3 sounds like the prop I'm looking for - between Raker and Ballistic - except that it's described with "25 degree rake, good lift, extensive cup". I take it as it provides the bow lift of Ballistic and the stern lift of Raker. I wanted it the be the other way around!

Any suggestions?

Engine: e-tec 60HP (2008), boat: Castello 533HT, 17.5ft, bow heavy, 2200lbs total weight including engine, family and gear.
Cruising speed: about 23mph, wot speed: about 34mph.
I'm living in a small country with limited selection of products available for testing. I'll probably need to import any prop myself, which makes returns complicated.

 

[steelespike]

Some time ago there was another 533T with the same complaint.From the videos at that time it appeared to me that the hull was designed
to lay down to more easily handle open water.34 sure seems like a reasonable top speed.
Perhaps you can find a dealer that will let you try some props.The Costello dealer comes to mind.
Tell us your prop size,and lightly loaded wot rpm and gps speed.RPM at the 23 mph cruising speed.

 

[Fed]

Is the step part of the hull vented to release suction inside the stepped area?
I saw a picture of one on the net that appeared to have an extra hole in addition to the drain plug hole.

 

[petterg]

I thought I was the only guy ever to come to a propeller forum with a Castello 533. I've never seen a video of the boat, just some pictures where the waterline seems to hit at about center of the boat.

Castello does no longer have any reseller in the country. I've contacted the manufacturer who said they've had the best top speed with a Raker.
I've tried Solas New Saturn, which seems to be the only SS in the area available for testing ("just" a 4 hours drive for a swap). Problem with New Saturn is that it lifts the stern far too much. Hence numbers aren't much worth. With the alu prop that came with the boat, engine hits revlimiter, so that doesn't say much either. I need to find a prop model before thinking about size. In case of a Raker, I'd go with a 20p. (Boat manufacturer recommends 18p, but they also recommend a alu prop that hits the revlimiter, so I'd go one size up.

Ventilation inside the stepped area sounds like a very good idea! I'll try to put a pipe down there (along the outside of the transom) to see if it changes anything. I wouldn't be surprised if it calls for mounting the engine one hole down.

Anyway, back to the topic of this thread. Does anyone know of a propeller that is less stern lifting than the Raker, and still bow lifting and suitable for high mounted engines?

 

[steelespike]

Some time ago the 4 blade was in discussion.The 4 blade was said to be stern lifting out of the hole and bow lifting at speed.

 

[SkiDad]

Powertech props. Check out Ken at propgods.com he will be able to help. I would call him.

 

[petterg]

Thanks for the suggestion for Propgoods. I've started a thread in Kens forum.

That 4blades goes from stern lifting towards bow lifting at speed was new to me. I've searched for the thread you mention, Steelspike, but can't find it. Do you remember how old it is? Did it have a title indicating a discussion about number of blades?

 

[steelespike]

Sorry, can't help.I was trying to find the 533 issue with no luck.
I believe many suspect search is problematic.
What is the present prop and performance numbers.
Do you think if you lower the motor one hole it might allow more up trim?
In looking around I did find the suggestion to not over estimate a props ability
to assist in bow lift.

 

[phillnjack2]

you wont find a better prop than a raker to give you bow lift, that's exactly what the prop is renowned for.
if you want the stern up a bit as well then put diol fins on the engine, and make sure its raised up as high as possible to get you moving fast off.
the raker likes the engine up .
have you looked when your on plane to see if the anti cavitation plate is touching water ? if it is then its too low.
you want the plate slightly above water when on plane to get best performance.

But your asking a lot from a little 2 cylinder etec, with 2200 pound weight.
it sounds like your too heavy up front, try shifting everything back and then try the raker.
now the raker is NOT a stern lifter at all, its called a Raker because of its 30 degree of blade Raker. whoever tells you its a stern lifter dont know what he is talking about.
cleaver lift the stern, as do low rake props, the higher the rake the less stern lift.
what pitch Raker are you using ? 18,20,22 or 24 ? I would think with your weight you should be using a 18 and 20 at max.

I am trying to find a raker for mine, as I need bow lift with my 70hp evinrude.

 

[petterg]

If I've given the impression that the Raker lifts the stern too much, there must be some misunderstanding.The argument against the Raker is it's fuel efficiency at cruising speed.
I don't have the Raker. The reason it came up as an alternative is the boat manufacturer saying its the prop that given the best top speed when they tested. I want something that give me better fuel economy at cruising speed, without giving up the other properties of the Raker.

The other alternative, get a prop similar to Ballistic that is more happy than the ballistic in near surface operation.

I think the Ballistic would be perfect, if it could handle running high i water.

I don't feel I'm asking too much of the engine. All I'm asking is a prop that doesn't require the water line to be above the av-plate to retain grip - and trailing edge cupping seems to lift the prop out water and lose grip.

Weight is moved as far to the back as practically possible. Next step would be add ballast.

Because of the stepped transom the water line (at plane) is quite high at the engine shaft even av-plate is 2.5in above boat bottom - and water is disturbed there. It's kind of like having a 1.5feet setback.

Lowering the engine causes water to hit the engine shaft, and splash into the boat!

The props I've tested:
Solas alu 15p (came with the boat), engine at hole #1: 26.4mph @ rev.limiter. Boat didn't feel good in waves. Water splashed in from the rear
Solas alu 15p (came with the boat), engine at hole #3: 27.6mph @ rev.limiter. Boat had a much better feel.
Solas New Saturn 17p, engine at hole #3: 32.4mph @ rev.limiter. Much better hole shot. Easily ventilating at plane. Bow was plowing. Could not trim out
Solas New Saturn 21p, engine at hole #3: 33.8mph @ 5800. OK hole shot. Engine sounds overloaded at cruising speed. Easily ventilating at plane. Bow was plowing. Could not trim out.
Solas New Saturn 21p, engine at hole #2: 34mph @ 5800. OK hole shot. Engine sounds overloaded at cruising speed. Could trim almost all the way out before ventilating, but bow would not lift.

Maybe my ventilating issues is caused by the disturbed water? I didn't think about that until now.

 

[phillnjack2]

you seriously need a raker prop, and I would say probably the 20 pitch. ( might be 19) need to try one out.
if you know anyone with one that would let you try it would be real good.
if you look on the bay you can find these raker props at good prices in good condition. you want the old raker with fixed 13 spline hub, newer are too soft.
it will give you a good holeshot and get that boat going properly.

they do seem to be the magic prop for boast that are bow heavy, not heard a bad word about them

 

[petterg]

Unfortunately I don't know of anyone with a V4 gear case having a SS prop.
I think PTR will be a better choice than raker. I think they are quite similar, but the PTR can be delivered without the vent ports. I think ports will be a disadvantage when cruising. (I'd love to see a comparison of the PTR and Raker.)

Ken at PropGoods suggests a NRS which is said to be between RED (similar to ballistic/rapture) and PTR. I think he might be right about that as he say the cupping on NRS includes the tip.

Thanks to SkiDad I found PropGoods forum. There are lots of test results posted there. It got my eyes reopened for the Viper. I earlier closed my eyes for the Viper because lots of people seems to complain about it's low cruising (20-25mph) efficiency. It needs higher rpm than others, and I assumed that meant higher fuel consumption. But what I found in the numbers posted is that the mpg for a given speed is actually lower than the other props in the comparison, even though the rpm is higher for the same speed. Then I wonder; Why does most boat/engine/porpeller tests compare results to RPM and not to speed? How often do boaters have a dialog like this: "Hey guys, lets go cruising at 3500rpm" and one guy respond: "Sorry I can't follow. My boat needs 4000rpm to keep your speed"? I've realized that I've been somewhat mislead by the tests conclusions.

In addition to Kens forum, I came across this test (where I suspect they changed a 7 for a 5 when noting WOT RPM for 18 Viper.)
http://www.evinrudenation.com/uncategorized/perfect-pitch/

There isn't much information available on the Viper. It seems to have high rake (how high? Similar to Ballistic or Raker?) and small blade area. How about cupping? And lots of users seem to run it high in water. To me it seems like no other brands has a similar prop.

How do you think a Viper would do on my boat?

 

[steelespike]

If I've given the impression that the Raker lifts the stern too much, there must be some misunderstanding.The argument against the Raker is it's fuel efficiency at cruising speed.
I don't have the Raker. The reason it came up as an alternative is the boat manufacturer saying its the prop that given the best top speed when they tested. I want something that give me better fuel economy at cruising speed, without giving up the other properties of the Raker.

The other alternative, get a prop similar to Ballistic that is more happy than the ballistic in near surface operation.

I think the Ballistic would be perfect, if it could handle running high i water.

I don't feel I'm asking too much of the engine. All I'm asking is a prop that doesn't require the water line to be above the av-plate to retain grip - and trailing edge cupping seems to lift the prop out water and lose grip.

Weight is moved as far to the back as practically possible. Next step would be add ballast.

Because of the stepped transom the water line (at plane) is quite high at the engine shaft even av-plate is 2.5in above boat bottom - and water is disturbed there. It's kind of like having a 1.5feet setback.

Lowering the engine causes water to hit the engine shaft, and splash into the boat!

The props I've tested:
Solas alu 15p (came with the boat), engine at hole #1: 26.4mph @ rev.limiter. Boat didn't feel good in waves. Water splashed in from the rear
Solas alu 15p (came with the boat), engine at hole #3: 27.6mph @ rev.limiter. Boat had a much better feel.
Solas New Saturn 17p, engine at hole #3: 32.4mph @ rev.limiter. Much better hole shot. Easily ventilating at plane. Bow was plowing. Could not trim out
Solas New Saturn 21p, engine at hole #3: 33.8mph @ 5800. OK hole shot. Engine sounds overloaded at cruising speed. Easily ventilating at plane. Bow was plowing. Could not trim out.
Solas New Saturn 21p, engine at hole #2: 34mph @ 5800. OK hole shot. Engine sounds overloaded at cruising speed. Could trim almost all the way out before ventilating, but bow would not lift.

Maybe my ventilating issues is caused by the disturbed water? I didn't think about that until now.

What is the rev limit?I used 6500 as max rpm is 6000
Ran these numbers through a prop calculator disregarding hole number only noting slip %. 15" @ 26.4, rev limit =23% slip,
15"@27.6 rev limit = 20% slip 17" @32.4 rev limit= 17% 21 @ 34 5800 = 21% slip.
Typical slip numbers are in low double digits. 12% average. Heavy or hard to push boats may be higher ... pontoons.
Slower speeds like cruising would tend to have higher slip. 21% slip is like a pontoon might have.
Perhaps you could post a video of the 21" at speed.Noting the planing attitude.
It appears that none of these props could get the bow up ?
.

 

[petterg]

The rev limit I found in spec was 6250. E-tec owners forum confirmed this. If this is wrong, my rpm readings are all wrong, as I used the rev.limiter as reference to calculate the tacho error. So if the limiter is 6500 my tacho is 20% off, which would make the wot with 21p become 6050. Based on the engine sound and feel I don't think it was that high.

New Saturn didn't allow the engine to trim all the way out. Hence the bow was plowing a lot more than with the alu. With alu the bow was high, but it wasn't plowing either.

I'll make a video once I get the boat back on water. (All thou video of propeller cutting ice could be interesting too.) It will be with the alu prop as I've returned the New Saturns. (The reason I tested New Saturns was the possibility to return them.)

Any thoughts on the Viper?
I see there are some used Vipers for sale on ebay. They are all painted black. I've heard that for salt water usage, I have to use polished finish. Is that correct?

 

[steelespike]

The rev limit I found in spec was 6250. E-tec owners forum confirmed this. If this is wrong, my rpm readings are all wrong, as I used the rev.limiter as reference to calculate the tacho error. So if the limiter is 6500 my tacho is 20% off, which would make the wot with 21p become 6050. Based on the engine sound and feel I don't think it was that high.

New Saturn didn't allow the engine to trim all the way out. Hence the bow was plowing a lot more than with the alu. With alu the bow was high, but it wasn't plowing either.

I'll make a video once I get the boat back on water. (All thou video of propeller cutting ice could be interesting too.) It will be with the alu prop as I've returned the New Saturns. (The reason I tested New Saturns was the possibility to return them.)

Any thoughts on the Viper?
I see there are some used Vipers for sale on ebay. They are all painted black. I've heard that for salt water usage, I have to use polished finish. Is that correct?

I was guessing on the rev limit. How did you establish your tach error. Tach error is seldom lineal.
Only way to do proper testing you need a accurate tach.

 

[petterg]

I compared engine sound change with tacho increase while accelerating slowly. That was to make sure the tacho were moving smooth in the full range.
When hitting the rev.limit the tacho showed 5400-5450. Knowing that the rev.limiter is 6250, this indicates real rpm being 15% higher than displayed on the tacho.
With the 21p tacho maxed at 5050. Adding 15% the real rpm is about 5810.
Another way would be to think of the error as linear. If so the max rpm with 21p was 400 down from rev.limiter. 6250-400=5850.
So with the two ways to calculate both saying real rpm is in the range 5800-5850, makes me quite sure that my guessing is near the true numbers.

I now have the cable to connect the pc to get the real readings. However the sea ice arrived before the cable, so I haven't tried it yet.

 

[steelespike]

Only way for accurate rpm is a accurate working tach. I don't think evaluating sound is likely to work.
Once the water softens Some accurate runs will help.
It's interesting having two the same models seeming to be bow heavy.
I wonder about the hull design is intended to handle rough going.

 

[petterg]

For my previous boat (in 1994) I didn't have anything but the engine sound, a stopwatch, a ruler and a map to calculate the prop size. I didn't even have a internet to tell me how to do the calculations and I had to figure out the formulas by myself. It worked out pretty good. I'd say having a gps and a tacho that can use the rev.limiter as a error correction parameter is quite an improvement.

Still the subject of this thread doesn't require any rpm data as it's not a question of prop size. Only the prop type in regards to lift, grip and cruising efficiency is asked for here.

 

[phillnjack2]

until you get a proper tacho you cannot work anything out.
the best prop for that engine to give you the best economy and top end and best cruise speed is a raker.
the gear ratio on the e-tec is real crap.
the props your looking for fit from 40hp to 140hp 13 spline. ideal prop to try is 13.5x18 and 13.5x20.
the e-tec just aint got the nuts to pull the 22 pitch .
the 3 cylinder johnsons and evinrude in longshaft (20 inch) have the right size props that fit your engine..
the e-tec 75 also has your spline and size gearcase and the older 90 e-tec.
all the guessing in the world will not tell you anything, without a tacho you dont even know if the engine is any good.
e-tec 60 limiter is around 6500. they do NOT hit the limiter below 6,000 rpm that's impossible.
But if you have a weak engine it might not pull upto this.
you must have a prop on that engine that can get to atleast 6,000 or you will burn it up by over loading the engine..
you can also try a ballistic in a 19 pitch.
your boat runs very wet, its the way its designed, nest thing to do is get a bow lifting prop RAKER and then if you want more bow lift get a jack plate.
the raker likes to run real high and ventilation is not a problem to the raker. put the right prop and then youl see the gps go over the 40mph barrier.
you wont get the same top end as the older 3 cylinder omc engines due to the stupid gear ratio and weakness of the e-tec powerhead.
But 40mph is not out the question with that boat and engine.
I would look for a 20 pitch raker Mk1 prop, not the new crappy Malaysia rubbish from solas, original mk 1 raker was made by omc and is a better prop.
you should end up with a slip figure of around 7% ro 10% at top speed, any higher and its propped wrong and wasting fuel.

I am now starting to play around with a ballistic 21 pitch for my evinrude 70, the e-tec 60 would never pull this, if you want a ballistic then 19 would be the very max.

 

[petterg]

The sea ice is gone, and I had some tests today. Thanks to ML1 at the etec owners forum, the mysterious rev.limiter behavior is cleared. The solution was simply to use the original fuel tank!

This was the first time with pc connected to the engine. I tested the 15p alu and a ported 19p Viper that I came across.

With the 15p alu, with the trim that gave the fastest speed according to gps, was 27.2knots (31,3mph)@5947, using 0.7738l/nm. Cruising speed 20.3knots (23.3mph)@4580, using 0.6206l/nm. Top speed is up by 3.3 knots just by swapping fuel tanks!

With the 19p Viper, with the trim that gave the fastest speed according to gps, was 29knots (33.4mph)@5580, using 0.7779l/nm. Cruising speed 19.4knots (22.3mph)@4080, using 0.524l/nm.
When trimming out more the boat started porpoising. At cruising speed I could hear the prop ventilating, unless the engine was trimmed all the way in. I think this happened because the speed is to low to block the vent holes. I'm planning to lift the engine two holes, then probably plug the vent holes.

Most tests comparing Viper to others say it has bad fuel economy at cruising speed. That is not true for my boat. Nor is it true in the tests I've seen where numbers are published, even thou the text claim it has bad fuel economy. Reason being that testers seems to compare fuel consumption at a given rpm, not at at given speed. I'd say a given speed is much more relevant for comparing.
People also say the Viper has bad low speed handling - I didn't notice any difference from the alu.