Anyone bolt their 9.9s to the motor mounts?

Post here for issues with outboard engines (i.e Yamaha 9.9) on PDQ yachts
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catalacmarc
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Anyone bolt their 9.9s to the motor mounts?

Post by catalacmarc » Sat Aug 17, 2019 4:16 pm

My boat has a heavy rubber over the motor mounts and not matter how tight you make the mount it tilts up some in reverse. With a previous cat, I was able to fix the mount with a lag screw set in epoxy (put it in, pull the lag and soak the resulting hole with epoxy, grease the lag and put it back in when the epoxy has mostly set). Curious if anyone has done anything similar? I did make a heavy rubber bushing between the heads of the lags and the motor clamp on the previous boat so that there would be something to dissipate the shock load on the lags.

Marc

danhaun
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Re: Anyone bolt their 9.9s to the motor mounts?

Post by danhaun » Tue Aug 20, 2019 7:00 pm

Yes. My 32 has 2.5 inch SS lag bolts through the rear bracket (2 each) going into the transom. But I have to remove these before pulling a motor for service or whatever. I have to get in the water to do this because access in not possible via the well (which is a problem in the winter). If I leave lag bolts out, there is no change in performance.


I am curious about the rubber on your mounts and often wondered if adding some vibration control would reduce the resonance when motoring. Could you post a photo or two?

Dan Haun
TomKat

catalacmarc
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Re: Anyone bolt their 9.9s to the motor mounts?

Post by catalacmarc » Thu Aug 29, 2019 5:15 pm

Dan, here are a couple of photos. This is a 1991 PDQ 36, the inboard sides of the motor wells are removable, gives good access to remove the lag screws when I want to pull the motor. The mount has a quarter inch sheet of rubber glued on both sides as well over the top. What I did was to drill and set quarter inch lag screws into the mounts as shown, remove them and epoxy the holes, then greased and reinserted the lags with the bushings. The second photo shows a bushing on a partially removed lag. After the epoxy cured, the lags actually came out. From the outside in, there is a stainless steel washer, two ~quarter inch thick disks of rubber cut with a hole saw on a drill press out of some rubber gasket material salvaged out of a local gasket company's dumpster, a metric stainless steel washer (14 mm inside?) that fits around the rim of a nylon bearing sleeve which goes through a nylon washer (you can't see it in the picture, it is under the inner stainless steel washer. The nylon bearing sleeve has a quarter inch interior diameter and is thin enough to fit into the hole in the motor mount, did have to shorten it 2 or 3 mm with some very course sand paper. The nylon bearing sleeve and nylon washer isolate the lag from the aluminum motor mount. I don't know how the wells work for the 32, but access is pretty easy for the 36 although the boat looses some maneuverability under power from the motors being closer to each other.
Marc
bushing 2.jpg

bushing 1.jpg

danhaun
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Re: Anyone bolt their 9.9s to the motor mounts?

Post by danhaun » Fri Sep 06, 2019 3:29 pm

Thanks, Marc. This is very interesting. ... wondering if anybody else has this setup.

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