Reply To: 1959 Sportwin Powerhead noise

[frankr]

bob-d wrote:

Hi all, just started a new to me 10 Hp 59 Evinrude Sportwin in my test tank for the first time. There was a distinct metallic knocking noise in foward under load, that went away at low revs in neutral.
Used the rubber hose method to try and pin point where the sound was coming from, it seemed to be the middle of the crankcase. I was thinking piston slap, but head area was quiet.
Compression is 75/70. Pushed a screwdriver against the pistons and no movement.
Ideas.
Thanks,
Bob D

I was ready to pounce on the classic 10hp clatter until I read your last sentence. Those motors are famous for beating the wrist pins loose in the pistons. The usual diagnosis is to follow the piston half-way down on it’s downward stroke with a screwdriver, stop turning and give the piston a push with the screwdriver. The looseness will show up as a clunk. The cure is pistons, rods, and wrist pins from a 1961-63 10hp.