Smooth At Last. 3 Blade Props & PolyFlex Mounts

[Lorin Smith]

I have an S2 8.5 I've owned since new and been well pleased throughout it's life but have always tolerated more engine/prop vibration than I thought I should. Delivered with a 12hp BMW and a 17" fixed 2 blade, over the years I ended with a Yanmar 2GM20F and 15" MAX Prop set at 22 degrees pitch. After another cruise this year having the fillings rattled out of my teeth it was time to address the issue once and for all. POLY FLEX engine mounts tamed the most of it. HUGE improvement (Yanmar recommends replacing their spongy mounts every 2 years! Yeah right) Still had vibration powering at 6kts, and went to a 15" 3 blade MAX Prop set at 20 degrees. SMOOTH AT LAST! It seems everybody else already knew 2 blade props create vibrations in the turbulent flow off the keel. The 3 blade does EVERYTHING better than a 2 blade.

 

[bugbitten]

I hate to think how old my 2GM20F mounts are. Where did you source your Poly Flex items?

John

 

[bugbitten]

To answer my own question:

"Thanks for your interest in Poly Flex. The cost is $241.40 each and you buy them from me.

Hugh CarrollThermo Boat Ltd.
Cell 1.250.920.5221
Office: 1.888.769.8495"

John

 

[BobM]

Are you sure that is each and not a 4 pack? On other sites he seemed to sell them as a 4 pack.

 

[bugbitten]

Bob,

I'd be thrilled if it were a four pack. Pleased if it were a two pack. But that's a direct copy and paste from his email. I guess if I were asking folks to spend $1K on mounts for a little Yanmar, I'd give them my cell phone number, too.

John

 

[BobM]

Just not worth it to me...

I just don't run the engine enough to warrant either investment...a $3000 prop or $1000 engine mounts. I will just adjust my throttle to lessen vibration if I hit a bad patch.

Bob,

I'd be thrilled if it were a four pack. Pleased if it were a two pack. But that's a direct copy and paste from his email. I guess if I were asking folks to spend $1K on mounts for a little Yanmar, I'd give them my cell phone number, too.

John

 

[bugbitten]

I just don't run the engine enough to warrant either investment...a $3000 prop or $1000 engine mounts. I will just adjust my throttle to lessen vibration if I hit a bad patch.

Ditto. I find my Yanmar smooth enough, particularly if it's used regularly and the prop's not in too bad shape. I sort of like knowing when it's unhappy and, like you, adjust the throttle (or get the prop cleaned) if it isn't. It'll hum along all day at 2700-2800 rpm, and, with a clean prop, will have no problem approaching it's redline.

I'm mostly interested in new mounts from a safety standpoint, as mine are of an indeterminate age. Sort of like chainplates: they look solid enough, but if they fail...

John

 

[BobM]

If they fail you have the luxury of a complete back up propulsion system...your sails. I agree that new mounts may be worth considering but lately I an finding that it is worth it to pay double for a direct replacement versus having to reengineer an improved version to save a few dollars. I just don't have the time. Look at my fuel tank. By the time I engineer the damn thing I could have paid 500 for a custom tank and been done already and sailing. Needless to say I went the route I did because I thought it would be faster, but it wasn't the case because I just didn't have the time to get to the boat.

 

[bugbitten]

If they fail you have the luxury of a complete back up propulsion system...your sails.

I recall a post - probably in another forum - where an engine mount had failed and the unrestrained diesel (it seems to me that it was kind of close to home - either an S2 or, at least, a 2GM20) promptly punched a cavernous hole in the bottom. They were near enough to shore that they were able to beach the boat and thus avoid a complete catastrophé, but not a happy situation.

John