[suffolkgateautomatio]

Hi Guys
I have an Alaska 600 and it is a great boat but at 20knots it starts to list to Port. we get 20knots at 3800 rpm so have lots of power left, we have a Yamaha 80hp and I believe it goes up to 5000 rpm. Does anybody know what could cause this to happen.
I have seen a youtube video of the same boat doing 30 Knots ok.

 

[Clinker]

Wouldn’t be surprised if the engine is mounted too low - where is the AV plate in relation to the bottom of the v in the transom?

 

[JonD]

Could be several things. Uneven loading of the boat, batteries, helm setup etc which aren't noticed at low seed but come into effect at speed.
Prop torque can cause a boat to lean, which can become more apparent with speed.
Hull design can also be an issue and the fact you've seen the same vessel doing 30kts ok doesn't actually mean much. That boat could have had issues which the owner has addressed.

First thing would be check loading on the boat and see if adding weight to one side will fix it, this can be done easily with a few drums of water etc.

The engine itself is another area to check. engine height and prop design could contribute to poor handling. Do you know anyone with a 4 blade prop you could try on your boat as a 4 blade will often help with a few issues, including stern lift. With the stern lifted and running higher in the water you may find it behaving far better.
Last resort are trim tabs, though propeller specialists will tell you no decent designed boats should ever need them.
Whats the hull itself like, does it have any obstruction or large transducers on either side.

 

[nab raider]

Years ago I had a Raider 18 with a 140 Suzuki and that engine was offset 40mm to one side to reduce that effect.

 

[cornishfisherman]

i had a 18ft rtk ridid raider with the ob offset its prop torque that causes it

 

[suffolkgateautomatio]

Thank you all for help, I will try all these suggestion in due coarse, when I bought my outboard I thought the prop a lot bigger than my last outboard so its possibly a cause of at least some of the problem