motor sounds like it's hitting bottom.

[Redfox03]

I have a 97 15hp mercury outboard that i bought last year. I noticed that whenever i get to about half throttle, it'll sound like the motor is hitting the bottom, but i'll be in deep water. it's like a thumping sound and the motor kind of shakes like i hit a rock or something. could this just be the prop coming out of the water? yes, i do have it trimmed all the way down in case you guys ask. i've checked it out and everything is in working order. i noticed sometimes it doesnt do it. could it be that it's digging too far in the water when i take off?

 

[Zum]

Still alittle confused about the question.
I will say that I don't think it's because of the last statement.
Only at half throttle it makes this noise?
Full throttle it disappears?

 

[thudpucker]

I'd bet its your shifting dog coming out of mesh with the Drive gear.
Better take it apart and see.
On the OMC's I've fixed that with a "Dremel" tool grinding wheel. Dont know about Merc's.

 

[Redfox03]

yes, it seems to only happen when i'm speeding up. sometimes it doesn't do it at all. I've noticed if i gradually speed up sometimes it wont do it, as apposed to just gunning it. thudpucker, how do i check the shifting dog? will i see it as soon as i take the cowel off?

 

[thudpucker]

I've never had a Merc lower unit apart, but on the OMC's the shifting dog is in between the FWD and REV gears, down in the lower unit.
You have to take the lower unit apart to see those gears.
As I said, I dont know about Merc's.

Go to Google with your engine numbers and see if you cant come up with a drawing or parts diagram. Then you'll know.