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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4716
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Stared by yahama 150 2 cycle started just fine but when I

Customer Question

Stared by yahama 150 2 cycle started just fine but when I put it in gear forward I here a noise from the lower far box, but when I start giving it more gas the noise goies a way. I only here it at idle. When I turn the prop with the engin off all feels tight. What Gould happen from last year?
Submitted: 6 months ago.
Category: Boat
Expert:  Jeff G. replied 6 months ago.

You're hearing noise from the lower unit correct?

Yamaha had a gear change in 2006 just to address this. In your case I have a couple questions and things I want you to try.

First, is this the same prop as you had last year? Do you hear the noise when the engine is in the water or just on the hose?

Yamaha also came out with a new hub design. Try this, take the prop off and turn it 1/4 turn and reinstall. Also make sure the splines are well lubed and the prop nut is tight.

Also check the gear lube that it is clean and new.

Do these and respond and we will go from there.

Customer: replied 6 months ago.
Same prop yesI bet not as I was on a hose.Drained the oil and and refilledHave not taken the prop, but what would that have an effect to this noise?
Expert:  Jeff G. replied 6 months ago.

I have had a few conversations with Yamaha service about this. In fact I have a 2010 F150 in the shop with the same thing. As I posted Yamaha changed the gears in 2006, so that is an option, replacing the lower unit, although expensive. I've had a couple that moving the prop on the shaft helped. Usually having the lower unit under load in the water and higher rpm and the noise goes away.

I bet you have a stainless steel prop. What is happening is the weight of the propeller and the lack of a load along with slow rpm and the shifter and gears are "rattling", "knocking".

Now if you get a ratcheting sound when trying to put it into gear, that is another problem.

So your options are to replace the prop, replace the lower unit, or don't run in gear out of the water.

Not a real common problem but one I've seen a few times.

Customer: replied 6 months ago.
am I doing any damage to the lower unit? Yes it is a stainless prop that clams with it.
Expert:  Jeff G. replied 6 months ago.

Yamaha says no damage. I've pulled gearcases apart to find no wear at all!

As long as there isn't noise while running you should be fine.

Try it with the prop off and if no noise, that is the problem.

Customer: replied 6 months ago.
the family was planing to go to the lake, but did not want to be one of the ones who has to be towed in because they did not check out there boat befor going out to the water. Sounds like we should be good to go as I don't here the noise when I. One off itle.This is a 1994 engin and just spen a lot to get it running good and she is running better now that it has in the past 10 years. But that said I don't see spending engin.
Expert:  Jeff G. replied 6 months ago.

Try what I posted above, it may help.

Customer: replied 6 months ago.
Ok will doThere is a very small play front to back on the prop shaft is this a problem?
Expert:  Jeff G. replied 6 months ago.

No that is normal.

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