Yamaha 115 losing speed and RPM in turns

[c130nav]

I have a 2000 yamaha F115 fuel injection four stroke outboard. I am not getting full RPMs of 5600 going straight and when I turn I loose speed and the RPMs go down. I am only getting 4200 RPMs going straight. What is causing the problem?

Thanks

[Woodnaut]

What type of boat is this on? Any chance of extra weight in the boat causing addition load?

[99yam40]

over propped, not set up properly, or a sick motor

[c130nav]

The motor is on a pontoon boat. No extra weight.

I check the compression and the compression is good.

[JB]

lose, losing

[Woodnaut]

130 - Double check your toons to make sure they're not holding any water and the boat isn't pulling more draft than it should.