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Charles, Marine Mechanic
Category: Boat
Satisfied Customers: 3309
Experience:  US Navy (Ret) Certified Mercury Marine Tech with over a decade of repair experience.
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I have an 05 Yamaha f250. Developed a loud whine, when in

Customer Question

I have an 05 Yamaha f250. Developed a loud whine, when in gear, increases with increased RPM's. Is also idling a little rough, and exhaust is loud..
Submitted: 2 months ago.
Category: Boat
Customer: replied 2 months ago.
I checked lube in lower unit. It was down to a few ounces, thick like mud, no metal chunks, and no water. I also cleaned fuel injectors, VST, and VST filter. Jumped fuel pumps, both operational, also running off external tank. Replaced water pump, and greased shaft.
Customer: replied 2 months ago.
Can't get over 5200 RPM's
Expert:  Charles replied 2 months ago.

Hello, my name is***** will assist you.

Expert:  Charles replied 2 months ago.

with the sound increasing with the RPM, this could really be anywhere on the engine. Start with a compression test and make sure that all 6 are over 180 PSI and with in 15% of each other. Then test the spark, you could just have a bad coil on the engine.

Customer: replied 2 months ago.
Charles, I forgot to include compression was #150 on all 6 cylinders, and all had spark. I even disconnected each plug, individually, with no change in operation. When I accelerate in neutral, the whine is not present, is present only when in gear.
Expert:  Charles replied 2 months ago.

Change the gear oil, it is not supposed to be like mud. Just 90W oil

Also, would you please post the full model number of the engine?

Customer: replied 2 months ago.
Charles, the lower unit lune was changed, water pump replaced, and shaft greased. Motor is a Yamaha f250 TURD,
6P2 U (###) ###-#### N
Expert:  Charles replied 2 months ago.

you are going to need to drop the lower unit and inspect parts 29 and 38. 29 would lead to loud exhaust, and 38 could be the source of the chirping sound.

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