Solid mounts

[fivepinhunter]

I have a 98 mariner efi 0g740194. I am looking at replacing my motor mounts with solid mounts. I do hit some stumps occasionally at idle. Has any body had experience with these mounts under similar conditions. I don't want to install if they are going to cause more damage. Thanks

[OldTimer57]

The first thing they will do is "buzz" every fastener in your boat loose. Screws in the console, front panel, etc.

The second thing they will do is remove any play caused by softer rubber mounts, if your boat is capable of 60+ it will help with chine walking.

The final thing is the vibration will annoy the heck out of you.

Of course if you hit lots of crap, a little give is better than a little break...

[Bruce2]

I have plastic mounts in my motor that i made out of delrin and vibration is not that noticeable as the plastic(delrin) has some give and absorption to it but not near the amount of the rubber ones. When i was searching for mounts i believe Sierra makes some of the delrin type mounts and Bobs makes some out of metal and i would think the metal ones would have more shake and vibration to them.

[91@Storm]

I have the solid mounts in my 98 150 and haven't had any issues.

[pt-73]

Solid mounts are standard on the high performance 2.5 Mercs. They are not an issue.

[skeeter91]

ive put solid(aluminum) in every motor ive owned(v6)only time i ever had a vibration issue was due to a unbalanced prop,bent prop shaft, or just before she blew up!

[OldTimer57]

It is definitely there. And there's no way to get rid of it. Solid mounts give much more precise control, and much more vibration. And the vibration is NOT caused by a bent/unbalanced prop. It is caused by motor power pulses (6 per revolution). At 600 RPM, that is ten revolutions per second. 60 power pulses per second which is a 60hz vibration. At 6000 RPM that turns into a 600 hz vibration which will buzz things. Whether they come loose or not depends on how they were put on. Nylock nuts helps a lot. Might need a touch of blue locktite on others, and on self-tapping screws that do things like hold windshield on and such. If you've never had soft mounts you probably won't notice anything that seems odd. I went from stock rubber mounts on a 92 XR6 to Bob's solid aluminum mounts, and I could definitely tell the difference. Not a bad problem at all, but it is noticeable.

Most boats I have driven have a "buzz" at higher speeds. If something is loose you will know it because you will hear it. IE an instrument where the hold-down strap/bolts are not tight. However, at the speeds we see, I much prefer solid mounts that keep the motor locked with respect to the hull. The less slop, the safer the boat is and the easier it is to drive and deal with chine walking issues.

[skeeter91]

[QUOTE=OldTimer57;9038777And the vibration is NOT caused by a bent/unbalanced prop. It is caused by motor power pulses (6 per revolution). At 600 RPM, that is ten revolutions per second. [/QUOTE]
so neither of these cause vibration but changing the mounts does?

[gaboy]

I prefer a softer material like uhmw instead of aluminum. what I dislike most is the aluminum of both parts will wear and the more it wears the more noticeable the vibration. replacing a softer material is an easy fix compared to fixing a mounting socket.

[EuropeanAM]

so neither of these cause vibration but changing the mounts does?

The stock (non-racing) mounts ABSORB vibration. Changing to solid mounts eliminates much of the vibration dampening.

It does, however, give a more more precise control feel (and can be very beneficial in high-performance applications).

[OldTimer57]

so neither of these cause vibration but changing the mounts does?

The motor causes the vibration, but rubber mounts help to isolate that vibration and keep it in the motor (and absorb some of it converting it to heat as the rubber flexes), not letting it transfer to the hull so much. Solid mounts and you get the "buzz" since everything goes right to the hull, which becomes a speaker cone of sorts. In a fast boat, I'll grudgingly take the vibration. :)

[scstarr]

Had them in my boat forever never noticed much extra vibration but with solid mounts and hyd. steering my boat drives like its on rails.

[OldTimer57]

so neither of these cause vibration but changing the mounts does?

No. They certainly WILL cause vibrations, of the worst kind. But with a perfect prop and shaft, the motor still vibrates. Closest thing to no vibration is an electric motor, and even they still vibrate since they have very short duration power pulses...

[cajunrgfm]

This is the reasoning behind both types

The stock (non-racing) mounts ABSORB vibration. Changing to solid mounts eliminates much of the vibration dampening.

It does, however, give a more more precise control feel (and can be very beneficial in high-performance applications).