Prop Data for Lund 1775 Impact XS

IDO,

I have a 2018 1775 Impact XS, running 115 Merc ProXS. I’ve been doing a lot of research on props since I felt I’ve been pushing my luck by running the river multiple times a week without a spare on board. I’ve got a question, but also wanted to sart this thread to document all of my findings in terms of propping this rig, since it’s a popular rig.

Here’s the current prop:
4 blade Merc Spitfire, aluminum. 13x17p. Top Speed 44mph (moderate load in boat, easy water conditions). Decent hole shot, we’ll call it baseline. 6k rpm at WOT, fully trimmed, 44mph. Cruising around 24mph at 3k rpm

Spare prop I just bought:
Merc Black Max 3 blade, aluminum. 13x19p. Top Speed 40mph (moderate load, easy water conditions). Improved hole shot over baseline. 5500 rpm at WOT, fully trimmed, 40mph. Cruising 30mph at 3600rpm, seems good on fuel but I did not collect fuel use data.

My research told me to run up a pitch when going from 4 blade to 3 blade. I could not locate a Merc 3 blade 18p so I had to go up to a 19. The research told me I should see higher top end but worse hole shot with a 3 blade. What I’ve found is the opposite with the prop configurations that I have tried. Did I miss something here? Or is it attributable to the fact that I increased pitch by 2 rather than by 1? Overall I prefer the spitfire, but the black max will make a good emergency spare which was always the intent to begin with.

My next setup is going to be a 4 blade, stainless from Turning Point (model Express Mach4). It is a 13.25x17p stainless prop. I will post results here when I get the prop and test it in the same conditions as the two aluminum props above.

Thanks

I’m surprised that no has jumped in with a reply. I think you answered your own question when you said you needed an 18 pitch three blade prop instead of the 19. It looks like the Spitfire 13×17 is a good match for your boat, that 6000 rpm at wide open throttle looks to be ideal. Too bad they don’t make props in one inch pitch increments, that 2 inch jump is a bit much in this case.

Moms hubby has same boat, I’ve ran it alot. Funny thing he called this morning needing a new prop and told him I’d be content with what he has on there, 4 blade spitfire just like yours. Handles as well as one would hope.

Jeffrey, I see what you mean. I really just wanted use this thread to document my findings with different props but also if anyone else wants to weigh in it’s welcome!

I’m hoping to get out and run some sea trials this afternoon with the new 4 blade 13.25×17 Stainless Express Mach 4 from Turning Point Propellers. Hoping this gets me back to where the spitfire was, if not providing a slight bump in performance.

Mr. Beads, yeah he probably should stick with that spitfire. it really is a great prop! I wanted to grab a stainless spitfire X7 but the price tag is a little wild for my taste so I decided to try out turning point. Findings will be posted later on!

Finally got to run the 13.25x17p Express Mach 4 from turning point and i am thoroughly impressed. 4 adults, cooler, and gear i was able to get 42mph. I also ran the boat with 8 adults (cruising not fishing) and was able to plane out and even hit 35 mph. Very impressive. RPMs at 6k at wot.

Looking forward to running it by myself to see what i can top out at I’m thinking probably in the neighborhood of 44.

Hi Kyle,

The normal standard of dropping one pitch increment from 3 blade to 4 blade (or conversely going up one increment from 4 blade to 3) generally holds true for older designs, but from everything I’ve read, and from some performance tests I’ve seen, this is not true with the Mercury Spitfire props. They were specifically researched and designed to be a one-to-one 4-blade vs 3-blade replacement in terms of pitch, intended to maintain virtually the same top end speed, but improve the holeshot, midrange performance and holding power over the 3-blades.

You actually see result that in your test case, where you lost 4 mph and dropped 500 rpm by switching from the 4-blade Spitfire 17p to the 3-blade Black Max 19p. I’m fairly certain that if you tried a 17p 3-blade Black Max you would see the same rpm and speed at WOT, but poorer performance in the midrange.

You see exactly the same thing in this video where they compared the 2 props, the same pitch Spitfire essentially matched the top end performance of the Black Max (actually gave them 0.2 mph faster, probably within the margin of error) but improved on everything else:

Now what I also understand about the Spitfire X7 versus the standard aluminum Spitfire is that it’s going to do even slightly better than the same pitch aluminum Spitfire because of its increased rigidity. It’s supposed to gain you even better holding power in turns, and a 1-2 mph increase in speed because you can trim it even higher than the aluminum version due to the better holding power.

I would hazard a final guess that if you compare the Spitfire X7 17p to your Turning Point Mach 4, you would see the Spitfire perform a little better as it looks like you lost a bit of speed with that compared to the aluminum Spitfire, and as I said, the Spitfire X7 will be slightly better than the aluminum Spitfire.

Cheers
TRJB

Hey TRJB, you’re correct on all accounts. The only thing I disagree with is that I lost top end mph with the turning point. The conditions of the test were, unfortunately, different and we have to account for that. I did “lose” 2 mph but I also had 3 additional people + gear in the boat. I need to get out on my own but I would hazard a guess that I will easily see 45-46 under the same optimum conditions as with my alum. spitfire.

I will say that I have no plans to test the merc stainless spitfire due to the fact that they seem to want over $500 for it. At the price point the turning point express mach 4 is the best prop I’ve tested in all aspects.

KPE wrote:

Hey TRJB, you’re correct on all accounts. The only thing I disagree with is that I lost top end mph with the turning point. The conditions of the test were, unfortunately, different and we have to account for that. I did “lose” 2 mph but I also had 3 additional people + gear in the boat. I need to get out on my own but I would hazard a guess that I will easily see 45-46 under the same optimum conditions as with my alum. spitfire.

I will say that I have no plans to test the merc stainless spitfire due to the fact that they seem to want over $500 for it. At the price point the turning point express mach 4 is the best prop I’ve tested in all aspects.

Kyle, did you buy your Turning Point prop from their website or somewhere else? I had a Turning Point on my previous boat and it outperformed all others, so I’m a fan. My boat is similar in size and power to yours, so I’d be willing to go with the same set-up you have.
Thanks for sharing your results and information.

Hey Robert,

I picked up mine from a friend who works for a distributor. Sounds like they have a decent stock of the turning point props though so should be easy to find one! They had no stock of the merc spitfire earlier this summer so that also factored into my decision.

I have an 18.5ft aluminum boat with the same motor. Shipped with Laser II 19 pitch. Getting about 43 mph @ 5800 WOT. Less than stellar hole shot and blows out from time to time. I’m going to drop a pitch and go with the 17p Spitfire X7 (currently on order). I’ll follow up with results if I’m able to run it yet this year.

FYI Supreme marine has some props you can pay $30 for and try out on the lake. I did this once, but had a bent prop shaft which ended up being my issue.

Finally ran my boat yesterday with only me and my gear with the turning point 13.25×17p express mach 4.

44.6 mph at 6k rpm. So i didn’t particularly increase top end however i lose next to nothing when i add weight; added 2 guys in identical conditions yesterday and i got 43.4 and maintained good holeshot. I also don’t blow out in turns anymore as I often did with the 13″ spitfire.

13.25×17 seems to be the optimal sizing for my rig. I’m sure any 4 blade in that size would perform nicely.