After almost 35 years in the hobby (off and on due to working, now retired!) I will be installing my first 4-stroke. I just purchased a Hanger 9 Pluse 60 XT and planned on installing a great used Magnum 91 4-stroke I purchased here on RCU. But I have a concern.

I ran the Magnum out at our club field on a home made test stand just to get familar with it. I guess I was not ready for the vibration difference between it and all the 2-cycle engines I've had over the years. The Magnum was smooth when at idle (and boy, that idle was great) and smooth at the top end (about 9000 RPM with a 14/6 Voss prop) but there was a couple of spots in the low midrange that I was really surprised by how much it vibrated.

Is this how 4-cycles are, should I purchase a special 4-cycle mount (like the Du-Bro) or am I just worried about something that is normal. The guys at the field thought it ran great, just looking for reassurance I guess.

Thanks