Performance prop for 25+ hp outboards! Merc Spitfire

I saw this new prop from Mercury developed for smaller outboards today and was wondering if anyone has any experience with it on here. It's a performance prop for motors 25hp-125hp. I know a lot of us are running motors in that range. Its supposed to give a superior holeshot without a loss in top end. And its aluminum so it shouldn't cost an arm and a leg.

https://www.screamandfly.com/content.php?105-Mercury-Marine-Unveils-The-Spitfire-Aluminum-Propeller

Depending on the price and figuring out which pitch I want to go with this looks like the prop im going to end up going with soon. It looks awesome! Its 40-60 hp right now and then the rest will come later in the year.

My Motor guy has been telling me about a prop that will be much better for my boat than what I currently have. It may be this prop? But I have a feeling he's talking about a yamaha 3 blade? This Merc prop may not fit on my 40 yamaha. but Im going to find out tomorrow. I have a few other mods I want to do in concert with a prop.

The reason I ask about this is becuase I was thinking of buying a new 70hp Yamaha 4 stroke but while researching I found this...https://www.yamaha-motor.com/assets/products/otb/bulletins/bulletin_4stroke_midthrustjetport_al_g3b_1756ccdlx_f70la_12-9-09_alm.pdf

It shows my boat only going 36mph WOT with the 70hp Fourstroke! I'm getting 33mph now with the 40 two stroke and a beat up prop. I remember BadBagger saying he was getting around 35mph with a 50hp. And another member getting 35mph with a 90/60 jet setup... Im not going to spend that kind of money on a new 70hp motor for only 3mph!

I have read that I can get an exhaust tuner for a 50hp yamaha and swap it out, and up my main jets 3 thousandths. I can also swap out carbs with a 50,60,70 hp motor (they are the same block) but carbs are expensive too.

I think the exhaust tuner, jetting adj, and new prop are the way to go. It should get me to about 35mph and pop me up on plane quicker.

Any advice is appreciated

reed youre on the right track with the tuner, jets, and prop. You might want to check on carbs though, i think some different brands will swap over with a yamaha. I know 40 hp tohatsu carbs will bolt on a 25 yammi.. Check local shops for blown motors that they want to part out or ebay for used ones

I have a 20 HP merc. Four stroker that I think should do more. Feels underpowered. Help appreciated.

I talked with my motor guy the other day again, and I printed off the Yamaha prop data along with the info on the Merc spitfire prop. He told me not to waste my money on the Merc prop, and not to do the exhaust tuner mod or the re-jetting to my motor. He said those mods would improve performance but it would not be as dramatic as I thought. Maybe another 2-3 mph WOT.

I trust him because he stands to make a lot of money off me by doing the work and me buying the parts through him. He did however suggest that I try out a Solas Amita 3 prop in a 12 pitchhttps://www.solas.com/newweb/propeller/products/brandSearch_rubex.asp.
I have the factory 14 pitch prop on there now, and while I understand how the 12 would help me get on plane faster I could not understand how a 12 pitch would be faster top end or even the same.

He explained that the factory 14 pitch was not allowing my motor to reach its max power or its optimum rpm, especially with a heavy load in the boat. With a heavy load it takes a min to get up on plane. He said that this 12 pitch prop is a bigger diameter and it has bigger cupped blades so even though it is pitched lower it will move a lot of water and get me up on plane quick, and also allow for the motor to get another couple hundred rpm.

Today I tried the Prop and just like he said it would.... the boat jumped out of the water on plane! Not just a little better either. It was a dramatic difference. I almost threw the dog out the back when I got out of the no wake zone and slammed the throttle down. It seemed to cruise on plane with less effort at slow speeds too.

The only dissappointment was that I didn't gain any top end. Im still right at 32 mph WOT. I guess thats good since I gained all the other performance out of it.... I hope to test it with about 4 people or so in the boat this weekend. He said that I would notice a difference with just me in the boat but I would really notice the difference when I put a load on it. He let me try the prop for free. I am going to buy it.

You will never gain top-end when going down in pitch, you're only helping load carrying ability. If your "factory" prop wasnt letting your motor make the right RPMs then i would think there would be another problem, but its a guess on my part.

I have never been happy with proping to the lower end of the recommeded rpm range. While theroetically that would get the fastest wot speed, most of the time in has been the same or maybe 1mph faster. Propping to the high end (lower pitch) has such an improved holeshot, that I can't be without. But, I probably do more stop and go vs long distance running.

Prop styles can be significant, depending on hull. I'll be interested in performance of the spitfire prop on jon boats.

fastcajun said:

You will never gain top-end when going down in pitch, you're only helping load carrying ability. If your "factory" prop wasnt letting your motor make the right RPMs then i would think there would be another problem, but its a guess on my part.

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His motor just isn't powerful enough to spin the bigger prop,with all the weight.
I don't think nothing is wrong with his motor,probably the 14 pitch has your outboard towards it's lower rpm range.
Your rpms went up,spinning the smaller pitch prop,so your speed stayed the same with a nicier holeshot.

If you had a real big pitch(15+) and it was lugging your motor(hurting it)a smaller pitch in the proper rpm range would give you better top end and performance.

Do you use a tach?
Has to be the most important tool when dealing with props.

Zum said:

fastcajun said:

You will never gain top-end when going down in pitch, you're only helping load carrying ability. If your "factory" prop wasnt letting your motor make the right RPMs then i would think there would be another problem, but its a guess on my part.

Click to expand...

His motor just isn't powerful enough to spin the bigger prop,with all the weight.
I don't think nothing is wrong with his motor,probably the 14 pitch has your outboard towards it's lower rpm range.
Your rpms went up,spinning the smaller pitch prop,so your speed stayed the same with a nicier holeshot.

If you had a real big pitch(15+) and it was lugging your motor(hurting it)a smaller pitch in the proper rpm range would give you better top end and performance.

Do you use a tach?
Has to be the most important tool when dealing with props.

Click to expand...

That is exactly what was happening. There is nothing wrong with the motor its GREAT! It's just that the 40hp motor wasn't able to reach optimum rpm with the factory 14pitch Prop. It was in the Rpm range but just at the bottom of it like you said... It wasn't lugging it but it just wasn't getting spun up all the way. Now with the 12 pitch it hops up on plane quick. I had 3 adults in it today and pulled a Tube. It hopped up plane today with more people and pulling a tube faster than it used to with the old prop and me by myself. It also cruises on plane at a slower speed 18mph. It cruises really nice at around 22mph. Im definately happy with the new prop! Best part is..... I still get the same WOT speed but I get there a lot quicker!

I do not currently have a tach installed. You may be wondering how I know it's turning a little more RPM now than it was and how my motor guy knew it. He said he could tell by listening that it was running around 300Rpm slower than it should under load at WOT. Sounds crazy but this guy knows what he's doing... Not surprisingly, when I put the new prop on I could hear that the motor was spinning faster. Not screaming but spinning just a little faster. When I ordered the prop last week I also ordered a Tach! We were going to see what my RPM's were with the factory 14 pitch and then see what they were with the 12pitch big blade prop. The prop came in but the tach did not! Monday If my Tach comes in and I get it installed I will see if his 300Rpm estimate was right. I bet it's close!

I have given up on the idea that there is a prop out there that will give you any more than 1-2 mph gain in top speed. 3mph at the most and that is if you are running a lower pitched prop than your supposed to. I supposed there is an exception when it comes to specialized racing props.

My last boat (the swamp Sled) had an 11 pitch prop on it when I bought the motor, and it ran 32 mph screaminglike it was about to come a part! I put a 14 pitch on it..... still ran 32mph but within its limits and not bouncing off the rev limiter. It got on plane no worse than it did with the 11pitch and after the change it got much better fuel mileage and ran smoother and quieter.

Props are a very funny thing to try and understand. If you try to put your logic on props in terms of gearing like on a motorcycle its wrong. If you try to put it in terms of traction your also wrong. Then you have slip and RPM to worry about. Its very complicated and I don't understand it.

Yes i run a Tach. I run right in the dead center of my recomended RPM range 5500-5900. I run a 13p prop. which is one up from a factory 12p prop. i didnt gain but 2-3 mph. I was trying to say that what came from the factory should be set to run at the premium RPM range and max performance.

fastcajun said:

Yes i run a Tach. I run right in the dead center of my recomended RPM range 5500-5900. I run a 13p prop. which is one up from a factory 12p prop. i didnt gain but 2-3 mph. I was trying to say that what came from the factory should be set to run at the premium RPM range and max performance.

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I doubt max performance,I picture more of a good all around prop,generic.(factory)
Theres know way they know what type boat there outboards go on,plus weight,hull style,etc,etc.
To many varibles so they put a middle ground prop on...IMO

My factory 14pitch prop on my Yamaha 40hp 2stroke was great on the 1756 G3 with only a 3 gallon tank, no gear, no cooler,and only 1 person.

Yamaha owns G3 boats and matches thier boats and motors/props. And while the prop was good an probably was within the operating RPM range at WOT, unloaded, and trimmed as far as I could get it up. The new prop is much better and is performing beyond expectations.

reedjj,

DId you get a new spitfire? Also what pitch prop are you running right now?

Fish2keel,

I did NOT get the Spitfire. I ended up getting a Solas Amita 3. in a 12 pitch. I went from a 11" diameter 14 pitch to an 11.4" diameter 12 pitch. Bigger blades with lower pitch! Same WOT speed with an unbelievable difference in holeshot and exceleration. Time to plane is now instant whether I have 1 person and no load or 3 adults cooler and pulling a tube. Plus the Solas was only $70.00 Bucks. The Merc Spitfire is in the hundreds.

I was originally trying to get both; better time to plane, and higher top speed but I guess that is impossible? Its either one or the other.

With your 1648 you should try the Solas Amita 3 in a 15 pitch!

Yeah I think ill try that prop out! I need a newer one so im going to have to give it a try. Where did you get yours? Id like to buy from someone in florida if I can help it but if not it happens. Im still trying to figure out how you figure pitch and everything. Im glad you didnt lose any speed I dont want to loose any top end

I ordered it through a local mech. but I think you can get them from the Solas Website cheap as well.

I'm thinking of trying a Solas Amita 4 blade prop on mine. They're just a little more expensive and should have more bite. I want to run my motor as shallow as I can get away with. Anyone here try one?

I saw the 4 blade as well. I was interested in it because of the 4 blade spitfire. I thought maybe it was just the Solas version of the same thing.

Remember I know nothing about props and don't pretend to. So I ask the expert about it. He said don't bother with the 4 blade unless you are running a tunnel hull and need to prevent cavitation. Or if you are having problems with cavitation on a regular hull. He said the 3 blade would be better for my boat (I don't know what you have) It has bigger blades and that is where the extra bite comes from, and you don't have the extra blade or the extra cost.