MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

pete059

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Jul 4, 2012
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Just purchased a sweet speed boat, the ELIMINATOR 234 Edge Powered by a MerCruiser 454BBC 7.4L (Chevy) & BRAVO-1 Outdrive that had vibration problem at idle. After pulling the front engine mounts shown below on the left (MerCruiser part number 814263 or 66284), I noticed that there was not much rubber to isolate any engine vibration from the hull. Being an engineer, I started looking into options to provide better isolation and talked to an engineer that used to work at the Stillwater OK facility. This engineer steered me to a mount that was used years ago called a Cushyfloat shown below on the right. I found the engine mount on the internet and it made a night and day difference. Apparently MerCruiser quit using these Cushyfloats because they were hard to get and more expensive. If you’re having any vibration issues, let me know and I can point you in the right direction. I did have to slot the bottom of the Cushyfloat to get it to line up on the hull.
Merc.jpg
 
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Fun Times

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Re: MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

Thank you for your helpful, informative post, I am sure it will be able to help others in the future.:)
 

Bondo

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Re: MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

Just purchased a sweet speed boat, the ELIMINATOR 234 Edge Powered by a MerCruiser 454BBC 7.4L (Chevy) & BRAVO-1 Outdrive that had vibration problem at idle. After pulling the front engine mounts shown below on the left (MerCruiser part number 814263 or 66284), I noticed that there was not much rubber to isolate any engine vibration from the hull. Being an engineer, I started looking into options to provide better isolation and talked to an engineer that used to work at the Stillwater OK facility. This engineer steered me to a mount that was used years ago called a Cushyfloat shown below on the right. I found the engine mount on the internet and it made a night and day difference. Apparently MerCruiser quit using these Cushyfloats because they were hard to get and more expensive. If you’re having any vibration issues, let me know and I can point you in the right direction. I did have to slot the bottom of the Cushyfloat to get it to line up on the hull.
View attachment 205461

Ayuh,... Welcome Aboard,... I've seen a few styles over the years, but not those,...

Ya Did re-align the motor, right,..??
 

pete059

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Re: MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

Ayuh,... Welcome Aboard,... I've seen a few styles over the years, but not those,...

Ya Did re-align the motor, right,..??

Thanks and Absolutely on the re-aligning of the motor. The part number for the Cushyfloat I used was 17-1609 with a 20mm stud. More info on them at Home - Mission Sales and Supply. They were very helpful in picking the right mount.
 

cobalt1999

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Apr 28, 2010
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Re: MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

What durometer rating did the company recommend for your application, two digit number after the 1609? That mount part # comes in 5 different grades.
 

pete059

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Re: MerCruiser 454 Chevy 7.4L Bravo I Vibration at Idle

What durometer rating did the company recommend for your application, two digit number after the 1609? That mount part # comes in 5 different grades.

I used a 70 durometer.
 
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