View Full Version : Z-21 Engine Vibration help

03-18-2012, 02:00 PM
70451well, It's 70 today, I've got the itch to get the Z-21 in the water. I'm an experienced Tech with Cars and trucks, but I need some input. Before I waste money on this project. My boat is an 87 Z-21 540 hrs new 350 last year. I bought this bought for the right price with an engine vibration at around 22-2600 rpm. I thought for sure I was going to find a bad outdrive input shaft. I removed the out drive last fall and put the water to it and started it up. To my surprise we still had the same vibration. Now my question is.... The boat is an '87, It has the outside bolt valve covers on it which leads me to believe it is an "86 or before engine. I do not know if mercruiser held on to the pre '87 two piece main seal engines thru 87 or what. If so I believe the flywheel can not be interchanged because the bolt pattern is different, but I believe the balancer can be. I am going to replace the coupler because it looks like hell. any advice on the engine situation would be a big money saver because when I do things like this, I usually way overspend and replace everything. A second question is, I may run this boat down at the cape this year, so fresh water cooling is a must. I put a fwc kit in my old checkmate senator I used to have and It was shoehorn and a prayer to get it to fit, just wondering if anybody had any insight to that, Thank you in advance, Andy.