finally got the infamous rattle out of my 08 250 pro xs. ended up being the bottom plate on the jackplate. it wasn't loose but it had a small gap most of the way around the 3 sides but touched in some places. took it off and grinded it down to where there is a small gap all the way around and now she's perfect.
just thought i'd share in case anyone else runs into it. i have a 10" bob's plate.
ha ha....i just tightened mine before my last trip out and the rattle stopped completely too.
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Geoff Bel
08 Blazer 210 Pro V w/07 Mercury 250 Pro XS
I thought you were gonna say that you looked at your lower unit and found a Yamaha sucked up into the low water pickups!!!!
Good find! We've noticed a little less vibration on "jackplate mounted" engines by putting a "small bead (5/16")of 3M 5200 Sealant" on the transom brackets prior to mounting the engine (even though "sealing the bolts is not necessary).
BTW... not sure what boat you have this on, but I think I heard that Bob's has a "thicker plate" for the bottom... might be worth the call.
Dual Mercury Master Technician- for Mercury Outboards, Mercruiser and Mercury Racing at European Marine in Greenville, SC.
Still consider myself a "Marine Apprentice" after 48 years (learn something new every day).
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My buddy's 2007 Ranger Z-22 has a Merc 250 Pro XS on the Bob's hydraulic plate and he has that same rattle in the 3000 RPM range. Apparently, that thicker plate isn't the solution. At least not for him.
I don't really have that rattle on my 225 Pro XS. At least it's nowhere near as loud anyway.
That's not it on mine. I have a 10" Bob's and the bottom plate is tight.
Still rattles like it is fixin' to go BOOM but it now has over 200 hours (2007 Z21) and it runs like it did from day 1.
Seth
I don't think anyone suspects that the rattle indicates that anything is actually "wrong" with the motor that could hurt it if not eliminated. Most are just annoyed with the sound.
Personally, I like it. I've convinced myself it's the carbon fiber reeds harmonizing. I loved the sound of the old Opti's that would chug, skip and miss at idle. Reminded me of the 3/4 race Isky cam in my old 57 Chevy with it's 301 motor (bored out 283), two 4-barrel Carter AFB carbs and Hedmann headers
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sethv »</TD></TR><TR><TD CLASS="quote">That's not it on mine. I have a 10" Bob's and the bottom plate is tight.
Still rattles like it is fixin' to go BOOM but it now has over 200 hours (2007 Z21) and it runs like it did from day 1.
Seth</TD></TR></TABLE>
the 4 bolts on mine were tight also, but it still made that horrific noise. grinding it down to where there was a small void on all three sides is what cured it. my noise could not be passed off as anything normal. it was really, really loud.
we also have a 31 fountain with twin 03 xs's with over 1200 hrs and they don't have the noise i had on the 08.
look at the edges of the bottom plate and see if it touches in some spots and not others. even though it doesn't seem to bother you, it might be worth fixing if it's as simple a fix as mine was.
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