More performance Yamaha 8HP 2 stroke

[zoojeeper]

G'day from Australia.
I'm chasing some info on upping the performance of an 8HP Yamaha 2 stroke outboard, whether or not it is feasible or even worth it. It's only done 20 hours so is still basically brand new. Have it set up with a 3.4m tinnie (Aluminium boat, Ozzie slang) and it is just barely getting on the plane. I know upgrading would fix this but I'm not ready to just yet and am just looking for a little extra performance. It feels like another 1HP would be enough. Any advice is extremely appreciated.

 

[robert graham]

Re: More performance Yamaha 8HP 2 stroke

Hot-rodding that motor for maybe 1 HP is not going to be cost-effective or a good idea. Just leave it like it is and adjust your weight in the boat towards the bow to help with planing. Enjoy it and buy a bigger motor later. Good Luck!

 

[Rosco 11]

Re: More performance Yamaha 8HP 2 stroke

Hey ZJ,
A fellow Aussie here . . . I have just a couple of tips to get the tinnie going better.

The cavitation plate on your motor ( the flat part above the prop) should be level or slightly higher than the lowest point of your keel. You may need to raise your motor on the transom. Don't lift it too high, or you might cavitate the prop. If it's too low, you will create more drag through the water . . .slowing you down.

Do you have a fin on the motor ? . They often help to get your boat onto the plane quicker.

Good luck . . .let us know how you go .

 

[Triton II]

Re: More performance Yamaha 8HP 2 stroke

Hey ZJ,

It might help you some more if we know some more. Which propellor are you running? What weight is the boat? A 3.4 dory/tinnie should easily plane on 8hp one-up so it must be either:

Motor not running well.

Prop to big or small.

Too much weight.

Too much drag (is the hull covered in barnacles etc?).

Once this cimmunity knows the answers, it'll be easier to help. Cheers,

 

[99yam40]

Re: More performance Yamaha 8HP 2 stroke

He is correct, do you know how many RPMs you are getting to at WOT and what the motor is designed to run