they are 1/2 bolts, but Mercury uses fine thread if you want to re use the nuts. Fastenal around here carries them.
The vibrations are only bad with the motor trimmed all the way down to the stops, and mostly in the 2000-2500 range for some reason. I noticed that one stop point on the mounting bracket was more worn than the other. I suspect that one side is slightly shorter and may be bouncing off the mountiing bracket. If my theory is correct, after the longer side wears down, in about 5 years, the vibrations should go away. In the meantime, I'll have to trim just up off the stops. After a few more test runs yesterday, I noticed that my claim of no bow rise out of the hole was incorrect. There is a very slight rise initially, but so slight compared to most boats that I didn't notice it at first. Depending on what happens with a boat load of people and a heavy pull behind, I may have to revisit the wedge option. One factor I had to point out to my son was that just like a high performance car, this boat is always going faster than it feels. I cautioned him about the speed of the boat when driving by others. Kevin
Kevin, My motor is now 13 years old and it still has increased vibration when it is against the fully trimmed in stop. In that situation there is metal to metal contact between the motor and the boat. When trimmed out a little the the trim cylinder rubber mounts are free to dampen out the vibrations. It only takes a bump on the trim to get rid of the vibration and since I run a wedge, I have plenty of in (or down) trim so I don't have to worry about it. HAHA. The Hydrodyne had a extremely stiff transom that seems to act like a sounding board. Most of the people that run these motors (like bass boats) only have two speeds---stop and wide open and the motors are designed with that in mind in my opinion. I think you will find that a full tank of gas and 5 people on board with a skier or two will make a difference. Your boat is a foot wider than an 18 which makes it a real load hauler and allows the tank to be mounted in the rear. I like your motor choice among the newer V-6's for the weight. You may find that the four blade has too much blade area for heavy loads. A three blade will let it spin up quicker (slip more) in a heavily loaded situation which gets the motor into the power band quicker. When my daughter ran the 150 Evinrude I wound up with an un-cupped 17 re-pitched to an 18. This is equivalent to about a 16 - 17 pitch in a typical steel prop with a little cup. jim
Jim, I concur. One bump up on the trim switch and the bad vibes are gone. The four bladed 15"x18p merc prop seems to work well. Maybe it's just because I'm happy with the overall performance of the boat and motor. So far I've tested the boat at tricking speed (12-16 mph) and it runs well. I'm getting a strong 47 mph at 5200 rpm for barefooting. I'm quite confident that this boat will do it all for us, including pulling the kite and holding a steady 38-43 mph with a load. I will try a three bladed 15"x17p merc prop later this spring and I'll probably opt for a wedge installation when my Merc Rep gets some extra time. The Optimax seems to run well at all rpm ranges. Almost everything I've been told about the 17.6 and the Optimax combo seems to be holding true,, and then some. Kevin
Kevin, Those numbers look good to me. That may be the right prop. My daughter's boat liked the 18 pitch also. I think the 17.6 is an all around good family boat. My daughter chose that boat because she thought the children would be less prone to falling out of it and she is familiar with all the Dynes. Just don't drive an 18 until you have the $$$ to own both of them. jim
Correction. I'm doing 47mph at 5600 rpm. After doing some 360's around the boat, I'm getting a bit of prop blow out coming out of the hole?? Not uncommon, but I was hoping a four bladed prop would have stopped that. I'm still working on my relationship with this boat. Kevin
Jim Do you know what lengths your bolts are - particularly on top? I can order these from McMaster-Carr and would like to get them ordered today. I think my current 5" bolts will work on the bottom but I'll probably to to 51/2 down there. I think 7" will work on top. I can get 1/2x13 in these lengths. Just curious as to the length on your top bolts because I know you have a wedge on there. Thanks!
