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MOP
06-22-2005, 10:21 PM
I am back to square (1) with the mystery noise! I took my last shot at it with the new wire set thinking a possible a low RPM cross fire issue, to a point it does sound like that. Believe me I know those type noises, never picked up rattles any on I/O's, but get on an inboard that has a tranny rattle you know damn well it has a cylinder issues.
Anyone know anyone from Merc that may know the general design/construction of the long snout Bravo coupler? I have stethocoped every inch of the engine, bell housing, starter and it sounds very good and normal. Several other good motor heads have said no way to an engine! I have black boarded the oil several times it is clean and clear, true it is only a visual but does show any crap in the oil. The only thing I can not check with the stethoscope while running is the coupler, I pulled the tin and checked the coupler bolts, tugged a few times and places on the flywheel, the mounts have been checked and rechecked. The noise is at its loudest at 5-600 RPM and can almost be be felt, it is off and on up until 900-1000 -0- at higher RPM it is sweet. It is not drive related, it did it before the drive went on. Need to get this one behind me!

Phil

Rootsy
06-22-2005, 10:25 PM
I am back to square (1) with the mystery noise! I took my last shot at it with the new wire set thinking a possible a low RPM cross fire issue, to a point it does sound like that. Believe me I know those type noises, never picked up rattles any on I/O's, but get on an inboard that has a tranny rattle you know damn well it has a cylinder issues.
Anyone know anyone from Merc that may know the general design/construction of the long snout Bravo coupler? I have stethocoped every inch of the engine, bell housing, starter and it sounds very good and normal. Several other good motor heads have said no way to an engine! I have black boarded the oil several times it is clean and clear, true it is only a visual but does show any crap in the oil. The only thing I can not check with the stethoscope while running is the coupler, I pulled the tin and checked the coupler bolts, tugged a few times and places on the flywheel, the mounts have been checked and rechecked. The noise is at its loudest at 5-600 RPM and can almost be be felt, it is off and on up until 900-1000 -0- at higher RPM it is sweet. It is not drive related, it did it before the drive went on. Need to get this one behind me!

Phil

did you remember to tighten down all of the nuts holding the windage tray to the main cap bolts? Did you set the height of the oil pump pickup correctly? or is it rattling against the bottom of the oil pan? did the pickup have a tab to secure it to a main cap bolt? did you weld the pickup to the oil pump prior to assembly?

jsut a few more "thoughts" fwiw...

JR

Just Say N20
06-22-2005, 10:37 PM
"It is better to keep your mouth shut and let people think you a fool, than to open your mouth and remove all doubt."

But, at the potential of being helpful, here goes. Our 31 express cruiser has two Crusader 270 hp V-Drives (Chevy 350). I couple of years ago, I began to hear a terrible noise from the starboard engine. It quickly got to the point of sounding like marbles in a can, but only below about 1,200 rpms. Higher and it would clear up.

Turned out to be the vibration dampener. I don't know if out drives even have such a thing; three sided thing that bolts to the flywheel, has a round center piece with 6 or 8 springs around the center with a spline in the center the transmission shaft fits into. The springs are to dampen the connection between the engine and the transmission. All the springs were worn to the point of being lose. You can see it inside the bell housing in the picture. I replaced it, and no more noise. Paid $120 for the first, and found another supplier and bought the second one for $65.

MOP
06-22-2005, 10:47 PM
Jamie garenteed not in the engine its self, I have rolled the RPM up and down for me and several others with the stethoscope the noise is out the back off the block a slightly louder when standing on the port side. The stbd side has more stuff to possibly block the sound, that is led me to pull it and check the mounts which were fine, the engine has a nice normal sounds at any RPM, several of my buds and myself have a ton of years racked up listening to the stuff. The last run I made trying the 24's added up to about 30 miles, performanced sucked a bit but ran great, good oil pressure and temp.

Phil

Good night have to be up at 5:30