Pontoon Boat & Deck Boat Forum

Does anyone have any experience with the Mercury Spitfire X7 4 blade (not aluminum)?

I have a Mercury CT 115HP 4-Stroke and get 26-27 MPH out of it at a WOT of 5200 RPMs running a PowerTec 15 x 15 Stainless Steel prop model ele3r15pms275.

I'm looking to get the RPMs up closer to 6000 to get it in the right operating range and not lug the motor. I'd like as much top end as I can get but RPM needs to go up to get the full benefit of the HP.

It's on a the Harris model in my signature... 4" wide lifting strakes on the inside of the toons.

This is a topic I am also interested in. I have been researching the aluminum spitfire for my Mercury 115 CT. I am running about the same speed with approximately 5600 rpm. I am curious if it is worth changing to the 4 are prop.

From what I have read, the 115 Hp is not powerful enough to significantly flex the aluminum prop. So the upgrade to the X7 is not necessary.

I wonder if the geometry is the same on both the spitfire aluminum and the X7. If it's a 14" diameter and same pitch with rake and cupping on the aluminum prop, no sense in spending the extra money on the X7 version.

I'm looking to see if anyone is running either spitfire X7 or aluminum on a pontoon boat and if they see a difference in performance and what that is.

I need to get the pitch changed and get the RPMs up at WOT.

I have the aluminum Spitfire 13.8x11 on my new 60hp Command Thrust. PN: 48-8M8026560.
I just did my two hour break-in for the motor last week and I can say I am impressed with it.

My last pontoon had a 60hp BigFoot with a standard 3 - blade prop. The 4 - blade has more more control at low speed maneuvering, plus a better hole shot. I was not able to get above 5500 rpm yet, but I have some water coming back over into the transom and need to raise the motor a hole or two still. Fully loaded in a 10mph breeze I got 20mph @ 5500 rpm.(gps) I expect that will increase rpm and mph a small amount.

Thanks for the information.

You current prop seem like it should be the proper one for your setup, your speed seems 4-5mph low since you have strakes. I'd expect your pontoon with that large displacement 2.1L 115 to run ~33-34mph. Have you played around with the trim much? Neighbor at the lake has a 21' twin tube with strakes and an older 1.7L merc 115 and his does an honest 34mph if you trim the motor out a lot,past 1/2 on the gauge, but will only hit upper 20's below 1/2 trim. My triple tube needs a lot of trim also, best speed comes from lifting the cones a good 1'+ out of the water. Another thought, Under skinning, but I'm assuming any modern pontoon with a strake package should have it included.

I have not played with it much. I just upgraded from 90 HP to 115-120 HP with the Simon tune. I had it out once since then. I am on the shallowest hole on the motor because I was way too deep and pushing lots of water onto the rear of the boat. I will try the trim and then drop it one hole, 3/4" to see if I can trim it up more. Does that make sense, trim, then drop a hole and try trim again?

makes sense to me, With strakes you should be able to make it porpoise with lots of trim (nose/bow bounce up and down on smooth water). If you can't, lower one hole and try again until is does. If you can and still have plenty of trim before the prop blows out then raise it 1 hole and try again. The perfect engine height is usually where it will just start to porpoise before the prop blows out. Mine runs its fastest (~38mph) trimmed right to where is starts to porpoise and will actually crack 40mph if I trim up more and let it porpoise a lot but that's not a fun ride (bow actually rises and drops 2 feet!) I'm raising mine up one hole before boating season starts this year, last season was my first year with the straked center tube.

Thanks. I am going to try the trim up to get it up on plane. If I can't because it vents/blows out, I'll have them drop it a hole (go deeper) and try again.

Where did you get your center tube and the approx price for it?

Got my center tube from Bill Boat parts in Missouri, payed 1200$ but I had to build my own transom as it was an outer tube that had 2 equal full length strakes. He also adds transoms to them for an extra fee. My build is in the rebuilds area of this forum.

Thanks for the info. I'll look up your rebuild post.