Tohatsu 3.5 Piston Mark

[Sea Rider]

Hola,

What happens to the engine if a psiton mark is placed upside down, this engine must have the piston mark arrow pointing to exhausst port, now is pointing to flywheel as in larger Tohatsu models. Engine is turning smoothly by hand.

Happy Boating

 

[RogersJetboat454]

Re: Tohatsu 3.5 Piston Mark

Either 1 or 2 things.

1.The wrist pin hole in the piston may be off-set as a counter measure for Piston rocking, noise, skirt wear, and to achieve a bit of a higher RPM. All that can be explained here;

http://www.motorcycleproject.com/motorcycle/text/cows-offset.html

So if you have the index mark for an off-set wrist pin in the opposite location as the one intended, you are going against the grain, and possibly having an adverse affect to all the ones the off-set pin is supposed to help.

2. Or the piston is ported in some way which I'm sure you would have noticed...

There is a reason why Tohatsu payed lots of money to those engineers to design your engine. If the outcome of flipping the piston upside down would work better, I'm sure they would have done that already.....

 

[Sea Rider]

Re: Tohatsu 3.5 Piston Mark

Big Thanks RogersJetboat454,

Very interesting tech article, so a slight 1 mm offset difference will give all that free trouble have proceeded to open the crank case and turn the piston facing down to it's recommended factory position. Accidentaly was about to screw that engine, you always learn something new with the help of others

Happy Boating

 

[TOHATSU GURU]

Re: Tohatsu 3.5 Piston Mark

"What happens to the engine if a piston mark is placed upside down"

Metallic dispersion in an energetic manner.