Phantom 18 Engine Height? (XL shaft)

[Phantom7]

Hi all,

I’m looking for some advice on the setup of a Phantom 18, as we’re fairly new to this and currently struggling to get the performance we’d expect.

We have a slightly unusual boat — it’s a phantom ‘venom’ (2017), the only one built using the original Phantom 18 hull mould but with a completely redesigned deck. It was rigged with an e-tec 130 and had only done 11 hours when we bought it last summer.

The issue is that we’re not seeing the speeds or performance typically associated with a P18 and 130 hp on the back. The motor is a 25” shaft, which means the propshaft currently sits 6” below the hull. It’s mounted on a manual power lift/setback plate that’s already at the top of its travel, so we’re now looking at using an XL-L shaft adapter (see photo) to get the engine higher.

Our main questions are:

• How high can we safely raise the engine without running into cooling issues?
• Will the transom cope with the engine mounted higher on both a jackplate and a lifting bracket? My thinking is the load is still primarily vertical, but I’d like to hear from those with experience.

For reference, with a viper 21p prop we’re currently maxing out at 51mph. We also tried a raker, but it was slower — likely because it’s buried too deep. We understand this is a relatively heavy Phantom 18 and aren’t chasing raceboat speeds, but it seems pretty clear that the current setup isn’t optimal.

Any advice would be massively appreciated!