1958 18hp seahorse sluggish

[Huntingducks117]

I rebuilt the carb and put new spark plugs in my 1958 18hp seahorse about 1 month ago. The motor ran great for the first 3 time out. I took it out yesterday and the motor would not go any faster than trolling speed. I took it home and cleaned the spark plugs and made sure that they were firing. They were dirty, but I cleaned them and they seemed to be firing good. I made sure that the prop was clean of fishing line ect. I took the motor back out, and no change. It was still running very very slow. The motor starts up great, and it sounds fine, but there is no power. Any suggestions on what else to check
Thanks

 

[JB]

Re: 1958 18hp seahorse sluggish

Have you looked at the throttle plate and stator to make sure they are advancing properly, and in synch?

Have you checked compression?

What happens if you pump the primer?

What happens if you squirt some fuel mix into the carb?

 

[F_R]

Re: 1958 18hp seahorse sluggish

It almost certainly is running on one cylinder. Basic checks as suggested by JB are in order. Add to that, a proper spark check. Sparking across the spark plug gap is not a proper spark check. It has to jump a 1/4" gap in free air.

 

[rolmops]

Re: 1958 18hp seahorse sluggish

I suspect the high speed adjustable needle(carburetor).These things have a tendency to vibrate out of place and loosen up.the next thing you know is that your mix is much too rich and it will really bog her down.