Prop disappointment

[QBhoy]

So
For the first time ever, I’ve been not impressed with a laser 2 prop.
Long story short, my new boat came with a 115 efi CT new outboard. Fitted to this when new, was a tempest plus of nearly 15” diameter and 19” pitch.
A bit of a ridiculous prop I assumed for such a boat. It’s a fairly heavy 19ft fletcher cuddy. Deep v but like all fletchers, manage to be quick things.
So with the 19” tempest, it seemed a little heavy for the engine and such a big diameter causes terrible torque steer too at anything other than slow or above my ideal cruising speed.
The engine would manage just over 6000 rpm and 43 mph gps, trimmed up. Incredible for such a set up...but me being used to the campion and it’s cruising rpm of about 2100/2200 rpm (different boat I know), the high cruising rpm of at least 3700 rpm on this boat seemed a little high.
So just to make sure she would be ok with a laser, I put my 19” on to see what happened. As expected the rpm hit the limiter but still managed 41mph. Not bad for a smaller diameter prop.
So. That’s it settled I thought. A good 21” laser 2 with its smaller diameter again will be ideal. Bring the rpm down and also be less harsh into gear and less torque steer. Better on fuel even too.
What a disappointment. It’s better at slow speeds and less harsh into gear...but the cruising rpm is around the same as the 19” tempest at about the same speed too. Then the biggest disappointment...she only managed 38 mph and this was at 5900 rpm. Angry !!
it looks like the tempest is a great prop really. It seems to grip better and allow higher trim and lift. Certainly over the 21” laser at least.
Just goes to show. The world of props. It’s never black and white.
19” enertia to try next...but it looks like a 21” tempest might be the way forward.

 

[QBhoy]

Oh and it’s worse on fuel cruising too.
I actually started to doubt it was a 21” for a few seconds. It reacts totally different to the 19” laser. Nowhere near the level of trim that it could manage without loosing grip.

 

[jimmbo]

Propping is a bit of a Crapshoot. What looks good in Theory, sometimes falls flat, and on Occasion, what seems ridiculous, works fantastically

 

[QBhoy]

Propping is a bit of a Crapshoot. What looks good in Theory, sometimes falls flat, and on Occasion, what seems ridiculous, works fantastically

Spot on. No such thing as a rule book with props. This is the biggest waiver from the norm I’ve ever seen to be honest.

 

[Faztbullet]

When I went to Waukegan years ago we asked about why some props ran better than others. Answer was mold differences for the wax castings and if it was made during a break as the wax ears would sag. That is why you can take 4 identical props from same MFG's and get 3 different results.

 

[QBhoy]

When I went to Waukegan years ago we asked about why some props ran better than others. Answer was mold differences for the wax castings and if it was made during a break as the wax ears would sag. That is why you can take 4 identical props from same MFG's and get 3 different results.

Yeah. Good point.
It’s so strange that the laser 2 19” ran better Than the 21” laser 2 top end. I could understand this if the 21” caused it to lag and made it run below the rpm range..but it didn’t at all. It was still near the top of the rpms. Maybe thinking that the smaller diameter on the 21” (13 7/8ths”) hindered it and the slightly lower rpm of the prop didn’t create enough lift.
Fascinating. I wonder how the 19” enertia will run. That has a diameter in between the 19” laser and 19” tempest plus.
Keen to try a mirage on it...but I need to be sensible at some point. Haha.

 

[porscheguy]

43mph on a boat like that with a 115hp is probably maxed out. A 150 would be much better, but you work with what you got.

My question is how does the boat feel with the different props? Is the motor buried in the water?

 

[QBhoy]

43mph on a boat like that with a 115hp is probably maxed out. A 150 would be much better, but you work with what you got.

My question is how does the boat feel with the different props? Is the motor buried in the water?

Hi there.

Yeah its doing very very well at that. I think that’s only 4/5% slip last I looked.
Funny you should mention the lift. I think that is the major difference. The tempest 19” is certainly lifting the hull out the water more than the 21” laser and a little more than the 19” laser.
The 21” laser is not allowing as much lift, presumably because of the smaller diameter perhaps. It’s the only conclusion I can make. It allowed no where near the lever of trim that the laser 2 19” did and was a lifetime away from the trim the tempest allowed. That was able to max out the trim without loosing grip. The laser 19 was similar but a mph or two off the tempest. The 21” was just nothing short of disappointing all through the rpm range really. Noticeable worse on fuel too on the smart craft at all rpm other than about 1000 rpm.

 

[QBhoy]

Worth adding that the fletcher hulls are always quick things long narrow deep v. A little tippy compared to the usual US boat though. But certainly better than any US similar sized boat I’ve ever been in, when it comes to rough water. Incredible thing.

 

[JFZ]

I'd like to hear how the inertia works out.

 

[Texasmark]

How did you get a 15" diameter prop on a 115 hp engine. I got a TP 14" Hustler on a 2002 90 2 stroke and had all of a ¼" to spare in not hitting the bottom of the AV plate....had to notch the reduced size trim tab. Compared to the 13+ standard inchers it was a smooth planing and easy cruising prop. 115 2 strokers run the same gear box and I have 13+ on current and previous 115s. Have no idea as to your engine nor boat.

 

[Texasmark]

How did you get a 15" diameter prop on a 115 hp engine. I got a TP 14" Hustler on a 2002 90 2 stroke and had all of a ¼" to spare in not hitting the bottom of the AV plate....had to notch the reduced size trim tab. Compared to the 13+ standard inchers it was a smooth planing and easy cruising prop. 115 2 strokers run the same gear box and I have 13+ on current and previous 115s. Have no idea as to your engine nor boat.

Eating Crow! Disregard these comments. After reading several postings about 90-115 4 strokers and the CT lower unit I had no idea as to what Mercury is up to these days. Should have "educated myself". Seems Merc. has had their design engineering department busy. Going to the Merc PDF and rolling through all the new engines and accessories it's quite a show.

 

[QBhoy]

How did you get a 15" diameter prop on a 115 hp engine. I got a TP 14" Hustler on a 2002 90 2 stroke and had all of a ¼" to spare in not hitting the bottom of the AV plate....had to notch the reduced size trim tab. Compared to the 13+ standard inchers it was a smooth planing and easy cruising prop. 115 2 strokers run the same gear box and I have 13+ on current and previous 115s. Have no idea as to your engine nor boat.

It’s one of the most recent command thrust models. Used the bigger gearcase and props from the 150 and upwards engines. Great reviews all round.
In one test they put the 115 CT up against the optimax 125 and the 115 CT beat the 125 in every department. Incredible. Even mercury were surprised. Top end, acceleration, economy and even manages to be lighter too. Amazing. It shares most things with the 150. I dare say it puts out more than the 115hp claimed.

 

[QBhoy]

Eating Crow! Disregard these comments. After reading several postings about 90-115 4 strokers and the CT lower unit I had no idea as to what Mercury is up to these days. Should have "educated myself". Seems Merc. has had their design engineering department busy. Going to the Merc PDF and rolling through all the new engines and accessories it's quite a show.

Yeah. They have went above and beyond with these new 4 strokes. Hate to admit it, being a big 2 stroke fan...but they have changed the game now. Well done to them.

 

[QBhoy]

I'd like to hear how the inertia works out.

I’ll be testing it ASAP. Let you know. I honestly can’t see it bettering the tempest and how that performs all round. 43 mph from a heavy cuddy 19ft hull and only 115hp. 1.5 miles per litre cruising at 23 mph gps approx. When it was on US setting. I’m sure it said 6 miles per gallon at that speed.
Thw enertia has made me eat my words before though. Never write that prop off again. Soon see.

 

[Scott06]

I’ll be testing it ASAP. Let you know. I honestly can’t see it bettering the tempest and how that performs all round. 43 mph from a heavy cuddy 19ft hull and only 115hp. 1.5 miles per litre cruising at 23 mph gps approx. When it was on US setting. I’m sure it said 6 miles per gallon at that speed.
Thw enertia has made me eat my words before though. Never write that prop off again. Soon see.

Will be interested to see how it works out. I found the same on a heavier beamy hull I needed more prop blade area. Found best top speed and hull lift with a revolution 4 , best holeshot with a Vensura, enertia fell in between. As per your results not xactly what you'd expect

 

[QBhoy]

Will be interested to see how it works out. I found the same on a heavier beamy hull I needed more prop blade area. Found best top speed and hull lift with a revolution 4 , best holeshot with a Vensura, enertia fell in between. As per your results not xactly what you'd expect

Glad to hear I’m not alone. Yeah it really seems the larger diameter is the difference. Thought about the rev 4 and aware that it would no doubt be a good prop on this, but by all accounts it is a 4 blade tempest plus. They aren’t cheap either and it’s likely to see a little drop in top end I’d think.
The enertia would need to perform some trick to be better I think. Although it has a larger diameter than the laser or perhaps the norm..it’s not quite as big as the tempest. I’m suspecting it might raise the cruising rpm and hit the limiter a little more readily than the tempest. But you never know. I was amazed at how it performed on the fast boat I have. There are many accounts of it doing well on a variety of set ups, where it probably shouldn’t be found. Eager to see what it does.
Im also tempered by the mirage plus at a 21”, but haven’t heard much about it on anything other than big big block fast boats. I wondered if the larger diameter might be a good suit to this mayne. An expensive gamble though.
Also wonder how a tempest 21” would fair. That may just be the perfect prop...but I am dubious whether it can get any better than I have it now. Would just love it if the rpms came down a little bit didn’t lose any top end or economy

 

[QBhoy]

Wanting my cake and eating it would be if the enertia managed similar performance and economy, but less torque steer and less harsh going into gear and got rid of the rumble at idle speed in gear. The big heavy tempest lets it’s self down here if I’m critical. The enertia must be about 2/3 the weight of the tempest being the X7 alloy. Soon see. Surely I won’t manage the illusive and impossible “perfect prop” scenario. Haha.

 

[jimmbo]

got rid of the rumble at idle speed in gear.

Rumble?

 

[QBhoy]

Rumble?

Yeah. Only happened with the heavy tempest. Not with the 21 laser or the 19 laser. Almost like the idle speed was struggling to be maintained. Defo not an issue with the fitting of the prop. It’s been off and on a few times.