Transmission Thump Noise - Yanmar

[Panamajames]

I have a Hunter 42 with a Yanmar 4JH2-TE engine. The question is when I shift from neutral to forward there is a thump. The other direction from forward to neutral there is no noise. Same with reverse. I alway reduce the throttle when shifting.

Another question please. What size hose comes of the mixing elbow. 3 or 4 inch exhaust hose. Mine is original and wire inside beginning to rust meaning leakage. I am not near my boat so I can not measure myself.

Thanks James

[senormechanico]

Our previous boat had a Yanmar 3HM35. The boat was 1 1/2 years old and had a thump when the engine was turned off.

I always thought it was normal.

Several years later, I found a broken motor mount stud. I replaced it and the thump was gone.