cliffm
Well-known member
- Joined
- Nov 25, 2021
- Messages
- 68
- Location
- Elliott Bay Marina
- Fluid Motion Model
- R-27 (Outboard)
- Vessel Name
- Wave Crest
There's been lots of discussions on exhaust hub length, so I thought I'd provide a graphics of the differences of the 3-blade props I've tested on our 2022 R27OB.
The shortest exhaust hub shown Yamaha SWSII at 5 5/8"
The longest exhaust hub shown Mercury Enertia at 7 1/2"
The middle exhaust hub shown Turning Point Mach3 OS at 7"
Based off Forum pictures, the longest option is Channel Surfing SCE5 modified/with 4" diffuser, which I'm guessing would total at 9 1/2"
The Sharrow MX3 appears to be less, maybe 8 1/2" but longer than any of the current commercial castings.
As many R27OB owners can confirm, the Yamaha SWSII 15P has a short "on plane" rpm range. Our R27OB responds better with the longer exhaust hub of the Mercury Enertia 14P staying on plane at +300 rpm lower than Yamaha.
Currently I prefer the very low torque steer response and manners of the Turning Point Mach3 OS 13P which is close to the largest radius that will clear the lower unit anode. Performance wise its extremely close between the Enertia and Mach3 with the Enertia a smidge faster top end and the Mach3 better mid and low end.
I have not tried/ran a PT SCE5 modified, but the published MPG is definitely above my best documented 3-blade MPG numbers.
Historically Mercury has had longer exhaust hubs on both the Enertia and Rev4 prop lines. Mercury's recent Enertia Eco prop line has an even longer hub at 8 1/4" along with a full 16" diameter, advertised as better MPG numbers than the previous 2.
All this data is showing the impact the exhaust hub can have on MPG numbers and prop performance.
When the PT SCE5 modified is available in a single stainless casting, maybe we'll join the 5-blade user club.
The shortest exhaust hub shown Yamaha SWSII at 5 5/8"
The longest exhaust hub shown Mercury Enertia at 7 1/2"
The middle exhaust hub shown Turning Point Mach3 OS at 7"
Based off Forum pictures, the longest option is Channel Surfing SCE5 modified/with 4" diffuser, which I'm guessing would total at 9 1/2"
The Sharrow MX3 appears to be less, maybe 8 1/2" but longer than any of the current commercial castings.
As many R27OB owners can confirm, the Yamaha SWSII 15P has a short "on plane" rpm range. Our R27OB responds better with the longer exhaust hub of the Mercury Enertia 14P staying on plane at +300 rpm lower than Yamaha.
Currently I prefer the very low torque steer response and manners of the Turning Point Mach3 OS 13P which is close to the largest radius that will clear the lower unit anode. Performance wise its extremely close between the Enertia and Mach3 with the Enertia a smidge faster top end and the Mach3 better mid and low end.
I have not tried/ran a PT SCE5 modified, but the published MPG is definitely above my best documented 3-blade MPG numbers.
Historically Mercury has had longer exhaust hubs on both the Enertia and Rev4 prop lines. Mercury's recent Enertia Eco prop line has an even longer hub at 8 1/4" along with a full 16" diameter, advertised as better MPG numbers than the previous 2.
All this data is showing the impact the exhaust hub can have on MPG numbers and prop performance.
When the PT SCE5 modified is available in a single stainless casting, maybe we'll join the 5-blade user club.
