Don't drop the prop

[Sheik]

have moved from an ali prop 13x17 to stainless 13 3/4 x 17 but from a prop that weighs around 1 kilo, this stainless one weighs about 5 kilos. Bloody heavy, and all in the centre by the feel of it, rather than in the wings orwhatever they're called. Anybody know whether this is normal for these props? My last stainless one didn't weigh wnything like this and I'm worried it might stuff the gearbox.

[Rodman]

I changed from an Ali to a solar stainless steel. It is important that the stainless steel prop is well balanced and it should not cause any problems. The first prop from solos was not balanced and caused the motor to shake and vibrate when motoring along as they give an exchange guarantee if you are not happy with its performance they will replace it which they did and the new prop is well balanced and the motor likes it.

ken

[Sheik]

OK, so that didn't work out... so if anyone has a spare 14x17 johnson prop kciking around, preferably ss would be willing to buy it...anyone...?

[trymyluck]

OK, so that didn't work out... so if anyone has a spare 14x17 johnson prop kciking around, preferably ss would be willing to buy it...anyone...?
So what didn't it do?

[Noelm]

yeah, agree, what didn't work? the weight of the prop matters little, all stainless props are heavy.

[Sheik]

The spline fitted but the sleeves didn't match at the front of the prop/back of the leg. The prop was too large a diameter even though the spline was fine. May be to do with Suzie /jonno mixture. Thinks it's the same leg on suzie 90-140 and needs 15 spline but also needs the leg and prop to match properly.
thanks for your interest.

[Moonlighter]

Help if we knew which motor we are talking about here. Guessing otherwise.

You mention Johnson/suzuki blend - so its actually a 4 stroke Suzuki painted Johnson white? What hp and year?

[Sheik]

OK, well thanks, motor is a 90 johnno four strokewhich I'm told is a rebadged suzi, prop I've taken off is a 3x14x17 ali.

[Moonlighter]

Ok, firstly, for all intents and purposes, you have a Suzuki outboard there. Nothing on it is made by Johnson. Its a Suzuki, painted white and they slapped a Johnson sticker on the side! Model sharing at its best.

The old Suzuki props that fitted their 2 strokes dont fit their 4 strokes. Plus, the 4 strokes run a different gear ratio and typically spin larger pitch props than equivalent 2 strokes.

For example, a 90 Yamaha 2 stroke will typically run well with a 17" prop. Whereas on the same boat, a 90 Suzuki 4 stroke would likely run a 19 or 20" prop.

My DF115 runs a 14 x 20 Suzuki stainless prop and this is frequently the best sized prop for that engine on many boats providede they are well matched to that hp engine. I pull 6200rpm at WOT with the boat loaded lightly, and maybe 6100 with a load.

To prop these 4 strokes correctly requires you to select a prop that will allow the engine to reach close to its max rpm at full throttle. Even if you never run at full throttle, you must test it and get to within a couple of hundred rpm of max, otherwise they do not perform well and you will be "lugging" the engine at cruise revs: A bit like driving a car at 40km/hr in 5th gear all the time. It is actually very bad for the engine to run it like that.

So, the question is, what max rpm could you get with the 17" alloy? That wll help you select the right sized stainless prop. And dont worry about the weight.

[gofishin]

...the sleeves didn't match at the front of the prop/back of the leg. The prop was too large a diameter even though the spline was fine... Sheik, it sounds like your are talking about the hub diameter, and that the prop hub diameter was larger than the gear case diameter or didn't fit in the gear case recess??

There are two sizes of hubs for larger props, commonly referred to as V4 and V6 hubs. With your motor you need a V4 hub with whatever prop make you choose.
Cheers



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[Sheik]

Ok, firstly, for all intents and purposes, you have a Suzuki outboard there. Nothing on it is made by Johnson. Its a Suzuki, painted white and they slapped a Johnson sticker on the side! Model sharing at its best.

The old Suzuki props that fitted their 2 strokes dont fit their 4 strokes. Plus, the 4 strokes run a different gear ratio and typically spin larger pitch props than equivalent 2 strokes.

For example, a 90 Yamaha 2 stroke will typically run well with a 17" prop. Whereas on the same boat, a 90 Suzuki 4 stroke would likely run a 19 or 20" prop.

My DF115 runs a 14 x 20 Suzuki stainless prop and this is frequently the best sized prop for that engine on many boats providede they are well matched to that hp engine. I pull 6200rpm at WOT with the boat loaded lightly, and maybe 6100 with a load.

To prop these 4 strokes correctly requires you to select a prop that will allow the engine to reach close to its max rpm at full throttle. Even if you never run at full throttle, you must test it and get to within a couple of hundred rpm of max, otherwise they do not perform well and you will be "lugging" the engine at cruise revs: A bit like driving a car at 40km/hr in 5th gear all the time. It is actually very bad for the engine to run it like that.

So, the question is, what max rpm could you get with the 17" alloy? That wll help you select the right sized stainless prop. And dont worry about the weight.

Thanks ML...
I've only had the boat for 6 months, and have barely had it out to get the revs up. Think it was probably doing 6k as far as I remember. Interesting that it might be able to cope with 19 inch. It goes seriously fast as it is, and holeshot with the 17" ali is amazing. Might lose a little of that to get more top end but it would be worth that as hole shot is like a jet ski with that prop.

[Moonlighter]

With a larger pitch prop and same diameter, provided you can still reach 6000rpm at WOT, the hole shot is unlikely to change a lot.

But no guarantees, if you change props from one maufacturer or model to another, the blade shape also changes and this can dramatically affect every aspect of performance, just ask Gofishin, he has tested dozens of them!

But speaking generally, you would be likely to pick up the cruise speed and improve fuel economy. This will be because you can achieve your cruise speed at less revs. As well, you would pick up some more top end, not that that is what you really want.

Cruise speed, ability to plane at lower revs and stay there in rough conditions, be responsive, and best possible economy is the goal for most of us.

A stainless prop grips the water better than alloy and has less flex. Sometimes it allows you to lift the engine up one hole, which also contributes to better fuel economy and better boat handling.

[Sheik]

Sheik, it sounds like your are talking about the hub diameter, and that the prop hub diameter was larger than the gear case diameter or didn't fit in the gear case recess??

There are two sizes of hubs for larger props, commonly referred to as V4 and V6 hubs. With your motor you need a V4 hub with whatever prop make you choose.
Cheers



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Thanks mate
that makes a lot of sense. very helpful.

[Sheik]

106660

OK, the plot thickens
Have just been on the blower to Mal at Central Queensland Outboard Service, who spent hours chasing up the situation with this prop for me. thanks mal, for outstanding service when I've never met the bloke before, and rang him cold asking about a prop he's advertised.
Anyway, Mal had a prop and I measured the one I've taken off and it's 100 mm dead on across the front housing where it fits into the gear box sleeve. According to Mal, this means it mightbe a yammie prop cause all the Suzi props are 110 diameter at this point.
Thanks again to Mal, and does anyone have any comment on that?

[gofishin]

All engine brands have their own props (or props branded that way) to suit both hub/gear case sizes.

From memory V6 size is 4 3/4", V4 size is 4 1/4". Don't know whether this is a 'nominal' size, the hub O/D or the recessed O/D, but I would guess not the recess.

Your photo shows a V4 hub size prop I would say.

Call SOLAS, they will be able to confirm.
Cheers


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[gofishin]

Sheik, measured the recess O/D of a spare V6 hub size prop I have. It is 110mm.

The prop you show in the photo (~100mm recess O/D) is definitely a V4 hub prop (I'm guessing it's the one off your boat?). Splines on Zukes, Yams and Mercs are the same (15 spline), not sure about Hondas. There are differences in some thrust washers.

If buying new for your boat, just ask for a V4 hub. If used, check the dimensions, or what donk it came off - as the hub size is not stamped on the props (unless you hunt down the details from the model number via Google etc).
Cheers

[Sheik]

Thanks mate appreciate your help.

[Sheik]

So put a 14x19 SS to replace the 14x17 originally on it. RPM WOT is about 5800.
Have to say I was expecting a little better performance, as I don't know about top speed (59kmh on new SS prop) but certainly less responsive and slower holeshot with new ss prop.
Should I be expecting a little more RPM than this?
Would the RPM and preformance improve if I lifted the motor?
Thanks again gurus
Jim

[gofishin]

Did you record some revs, economy and speeds for both props?


...RPM WOT is about 5800. ...Should I be expecting a little more RPM than this?... What load; people, fuel, gear etc? From memory these donks rev out to 62, don't they? I would probably be looking for more revs.


...Would the RPM and preformance improve if I lifted the motor?... yes and yes... Normally! But it depends on how high it already is, what sort/type of prop, what condition it is in, pod and type etc, and the type of boat too.

How easy is it to get the current prop to start ventilating? Turns, trim etc?
Cheers
Brendon


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[Swanie1975]

A 14x18 genuine suzu 3 blade stainless prop sounds like it would be on the money for your set-up.
they perform far better than the solas stuff that's stamped the same size and pitch.
suzuki four strokes can be bitch to get right, especially the 90-115-140 hp range.

Cheers Ryan