Motor noise

The other day I was out I managed to hit a submerged log with my 25hp Johnson. Now, when im wide open, the motor gets louder right at the peak of top speed. It almost sounds like the exhaust gets lifted out of the water a little. So it just might be the exhaust out the prop I'm hearing.

The lower unit looks ok. The aluminum prop looks a little chewed up on all the blades, and one of the blades is bent back. Would the bent blade cause the motor to lift up a little more on WOT causing the thru-hub exhaust to be lifted out of the water? I am ordering a new prop soon, but wanted to know what you guys thought.

I would expect that the prop damage you described could cause some cavitation problems and that might possibly make the through hub exhaust noises louder than normal. But I would expect that cavitation to reflect noticeable changes in your top speed also.

There is a slight drop in top speed. It doesn't have the loud exhaust noise when idling. Just on the end of running wide open and hitting top speed. That's why I am assuming the bent blade is lifting the prop exhaust up slightly out of the water and why I can hear the louder exhaust sound. I am hoping thats the problem anyway.

If the prop is bent anyways I would replace it and see if it goes away. Cheap place to start

Yeah, I just ordered a new prop. I will get the old one repaired for a backup. Hopefully the new prop fixes the problem.

I bet it's cavitation too. May not be cavitating until a certain (higher) rpm.

Did the reverse lock trip when you hit the log?

[url=https://www.tinboats.net/forum/viewtopic.php?p=354418#p354418 said:

waterman » 18 minutes ago[/url]"]I bet it's cavitation too. May not be cavitating until a certain (higher) rpm.

Did the reverse lock trip when you hit the log?

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Yes, the motor jumped up a little releasing the lock.

It has to be some type of ventilation/cavitation issue. I found this video that kind of explains what I think might be happening.

https://youtu.be/YJA_4oND8lU

what year is your motor? if its pre early 90's you don't have a thru hub exhaust....

[url=https://www.tinboats.net/forum/viewtopic.php?p=354441#p354441 said:

shawnfish » Today, 05:36[/url]"]what year is your motor? if its pre early 90's you don't have a thru hub exhaust....

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1999

New prop on and good as new. =D>

jojo,

I'm PLEASED that that fixed the problem. - I was afraid that you had "torqued" the foot & that's a HARD fix.

yours, satx