Using old mast mount to mount newer Radome

[evm1024]

Currently I have a radar pole aft with a Raymarine 24" 4KW HD radome on it. The boat originally came with an old, non-functioning, Raytheon radar with a M88390 mast mount.

The old radome a uses 5 9/16" by 5 9/16" square mounting pattern. And the HD radar of course uses a different pattern (9.17" x 5.5").

Has anyone mounted a "new" radome on and old mast mount with an adapter plate?

The frugal part of wants to get an adapter plate and keep the number of holes in the mast to a minimum.

The safety part of me says get a new mast mount and be sure of the strength.

Do adapters exist?

[a64pilot]

Easy to make an adapter, last boat I made the whole mount. The newer Radar is likely lighter as well, but that would be my concern, to ensure the new Radar isn’t heavier, most likely not, but worth checking.
Why do you dislike the pole?

[evm1024]

Originally Posted by a64pilot

Easy to make an adapter, last boat I made the whole mount. The newer Radar is likely lighter as well, but that would be my concern, to ensure the new Radar isn’t heavier, most likely not, but worth checking.
Why do you dislike the pole?

My thoughts exactly RE weight.

I see a solar arch in my future. We are prepping for a 5 year cruise. At first I thought that Covid-19 would push us out till next year. But perhaps Mexico will be open and "safe" this fall/winter.

[ggray]

This won't address modifying your mount, but may still be useful.

I replaced an 18 year old Raytheon with a new Garmin, and while the hole patterns were the same, the base footprint of the old one was toward the front of the radar, and that of the new one was toward the rear of the radar. We are talking about a matter of 8 inches or less.

I realized then why the newer Raymarine (it too was a replacement) on a friend's boat looked oddly too far forward on the pole mount. Same base situation.

Reading in the manual of my Garmin prior to installation I found reference to "offset". I asked Garmin if I could mount the new radar "backwards" and set as much as a 180* offset, and then come out right. They said yes.

So as well as accommodating the different hole pattern you may find out that you want to do the same to keep the radar in the right place front to rear.

[Smokeys Kitchen]

Originally Posted by ggray

This won't address modifying your mount, but may still be useful.

I replaced an 18 year old Raytheon with a new Garmin, and while the hole patterns were the same, the base footprint of the old one was toward the front of the radar, and that of the new one was toward the rear of the radar. We are talking about a matter of 8 inches or less.

I realized then why the newer Raymarine (it too was a replacement) on a friend's boat looked oddly too far forward on the pole mount. Same base situation.

Reading in the manual of my Garmin prior to installation I found reference to "offset". I asked Garmin if I could mount the new radar "backwards" and set as much as a 180* offset, and then come out right. They said yes.

So as well as accommodating the different hole pattern you may find out that you want to do the same to keep the radar in the right place front to rear.

+1
Just did this two weeks ago. Took off the old Raymarine unit and mounted a new Simrad 4G unit. The new bolt pattern was in the same holes, just offset a little more towards the rear of the dome.

Since my cable exits the rear of the dome in a recessed path, I left the dome a little far forward to allow the cable to just drop straight into the existing mast opening without wrapping around the dome or mounting foot.

[stormalong]

I did this 20 years ago when I replaced a Raytheon R20X with a newer Raytheon. I used 3/4" King Starboard to make the adapter. It is still in use today. King starboard is a great material for this as it does not deteriorate from UV.

[evm1024]

Originally Posted by stormalong

I did this 20 years ago when I replaced a Raytheon R20X with a newer Raytheon. I used 3/4" King Starboard to make the adapter. It is still in use today. King starboard is a great material for this as it does not deteriorate from UV.

Sounds like a good option. Thanks

[ggray]

Originally Posted by Smokeys Kitchen

+1
Just did this two weeks ago. Took off the old Raymarine unit and mounted a new Simrad 4G unit. The new bolt pattern was in the same holes, just offset a little more towards the rear of the dome.
.

I attribute that why what I did was not done on my friend's boat is that his installation was probably done by a "professional" who just threw it up without thinking how it could be done better.

A better job can be done by whoever will live with the results.

[smac999]

Make a plate with 3/4” starboard. Countersink bolts to bolt new plate to pole. (Which is why it needs to be thick) if bolted from top. Bolts in way of new radar.

Make new holes in starboard. This only works if the new holes are wider then the old mount and miss it. (If it does not miss it, just drill 4 new holes in pole)

[CaptNemoO2]

I replaced an old 24' Raytheon radome (circa 1993) with a new digital 18" unit. Same issue with the hole pattern. On my mount, I wouldn't have access to the mounting hardware to the actual radar so the adapter plate had to go on the radar first, then on to the mount. The problem then is there's no access between the plate and the radar to tighten a nut and bolt to secure the whole thing to the mount. I installed stainless tee nuts from the top of the adapter plate in the hole pattern for the existing mount. Then I counterbored the hole pattern for the new radar on the underside of the adapter plate. The c'bore was big enough to fit fender washers, and deep enough so the underside would be flush. The radar is then secured with bolts and fender washers into the molded in threaded inserts in the radar. Plop that onto the mount, and screw it down with bolts and washers into the tee nuts. Like others said, starboard is perfect for this. I used 1/2" thick. Stainless tee nuts designed for wood have prongs that dig in to prevent spinning; those prongs go right into starboard without issues. I also used a flush trim router bit so they plate is exactly the same size and shape as the bottom of the radar.