what's wrong with my boat?

[laopi]

Hi,

I had a 90's 40 HP mercury,  when I drove on lake today, the reverse and forward with low speed all fine, when I try to speed up, I heard a very load noise from motor, and speed  won't change.

Thanks.

 

peter

[grimsbylander]

Sounds to me like either the adjustment is off on the gearbox cable or your prop hub is shot and the load is causing the prop shaft to spin inside the prop.

Edited May 30, 2020 by grimsbylander

[cheaptackle]

I have seen/heard many times lately with this same symptom and they all had pictures/stories of the trailer still attached to the boat in the water.  Hope this is not the case here.  grimsbylander nailed the two possibilities with the easiest fixes.  Worse one is gearbox is shot.  If you are not mechanically inclined have it checked - should be a quick diagnosis (fingers crossed) and hope it's just the adjustment.   New prop won't break the bank, that you should be able to tell yourself just by manually spinning (in neutral) it and see if the hub spins too.  Good luck!

[Garnet]

I think it's your lower unit. Check your oil level and metal shards.

Do a compression check. They will run sometimes just haven't flown apart. 

[EE_]

for a 30 yr old motor, there's a possibility of a worn clutch dog that cannot maintain full engagement with the forward gear when under higher load transmission

[Headhunter]

Check you coils, 30 year old boat and all!

HH