Card in spokes noise from back of engine
 

Just as the title states, I developed a strange noise from back of engine after pulling boat to town to get gas. Last Wednesday I dropped boat off lift and idled over to the ramp to load boat on trailer. Everything normal on 2 minute trip to ramp and while loading boat. Make the 20 mile round trip to town to fuel up (not paying more than double at Marina than I can pay on road) and after backing down ramp to launch as soon as I went to turn motor over you could hear what at the time I thought to be the boat in gear and the props hitting something. WTF?! Double check everything...boat in neutral, drive properly trimmed down, boat plenty deep in water, etc. Pull boat forward and everything looks good at back of boat. Put boat back in and go to fire engine and same thing, "thwap, thwap, thwap, thwap...". I stick the boat in storage and call it a day. Saturday I bring the boat home and start the investigation working from the back of the boat forward. Pull outdrive. U-joints (perma-lube) are intact and move freely with no binding. Driveshaft splines look like new and have plenty of grease. I rotate drive by hand since it is in gear after pulling and drive rotates smoothly with no grinding, binding, etc. Stick a light up into transom assembly and can see the coupler splines look new and have plenty of grease. I stick my hand up through the bellhousing and rotate the gimbal bearing and it turns smoothly. Insert the alignment tool and the alignment is good and has not changed since last time I pulled drive. While the drive is off the boat, I pull the kill switch so the motor will not fire and turn the motor over a couple times. I now do not hear the noise. I grease the gimbal bearing, clean and grease the driveshaft splines and reinstall the drive. Next I drain the gear lube. Both magnets are clean and the lube still golden in color (Amsoil) with no evidence of water. Drive is refilled, muffs installed, water on, and fire engine. "Thwap, thwap, thwap, thwap...". Beer thirty.

Yesterday I have a buddy come over so I can get an ear near the drive while the engine is running. I hear no unusual noise in the upper with the engine running. I step back and have him put it in gear both directions. Drive goes right into gear with no unusual noises. Now I crawl as best I can in the bilge. It is a tight fit as the rear seating is over the top of the engine and the back of the engine extends underneath the swim platform a good bit. Buddy fires the engine again and it is clear the noise is coming from somewhere around the back of the engine or in the transom assembly. I can see the snout of the coupler (long steel hub) and best I can see/feel nothing has fallen onto it from above (if it had, it should have made noise with drive off). What little bit of the driveshaft I can see has nothing near it.

The big stumper here is everything is fine on shutdown at ramp and then 30 minutes later, after doing nothing but taking a ride on a trailer, everything is fubar. So, my question to you all is have you ever heard this type of noise before from the back on your engine. Again, it sounds just like the old playing cards in the bicycle spokes noise only a bit more metallic in nature. Can raising the drive all the way up in trailer mode tweak the gimbal bearing (has 400 hours on it) and now it is toast? The noise does not sound like a typical bearing noise and again, the bearing rotated smoothly by hand. I've never lost a gimbal bearing so I don't know what they sound like bad. What else could it be? I was thinking something with the flywheel/coupler/flywheel cover but if that was the case why did it not make the noise with the drive off the boat? I really don't want to pull the motor if I can avoid it.

Boat is a 2004 Chaparral 260 SSi, 496 MAG, Bravo III drive. Engine serial number OM683216 (for BUP! ). I don't have the drive serial number in front of me as the Simrek Halo drive shower wore the decal thru right where the serial number is. I'm sure I have it in my paperwork somewhere.

Fire the motor up with out the drive off, Its fine to run it for a few seconds. See if the noise is still there.

This may sounds stuipd but have you closley inspected your serptine belt? I have seen where they look fine till you run them and they have a loose rip that gives you that smacking sound.

Just shooting from hip here. I could have swore I had a rod knocking in an old s-10 but Oil pressure was good. Ended up the flywheel was cracked. Also changed in gear and out of gear as load changed. Severity increased with more load. I'd probably look toward coupler/flywheel and closely inspect that area. Only so many things it could be back there..... I also had a loose pulley throw me fits but you stated it was definitely coming from rear..... I thought also of internal exhaust flapper, but you stated it didn't do it while testing with drive off. Good luck

Belt is good. No accessories are making the noise. Noise is emitting from back of engine area. Turning over motor with pulling kill switch results in no noise. I'm not firing motor with drive off as I have no fresh water flush attachment to supply water and I don't feel like wasting an impeller. With the drive on, before the motor fires you can hear the noise as the starter rotates the engine, The engine does not have to fire to hear the noise. I never lit it off at the ramp when it first did it on arrival back from gas station. I was hoping it was a water pump, power steering pump, alternator, etc. but no noise from front of engine.

Thanks. Yeah my fear is it is in the flywheel/coupler area. You would think it would do it without drive installed but maybe the driveshaft being inserted in the coupler puts enough load on it to where the problem will show up. It sounds like the flywheel is hitting the flywheel cover. Like maybe a bolt has backed out. But man if that is the case why does it not do it with drive off? I simply do not have enough room to get any good view of the area with engine in boat. I barely have room to change the IAC on the engine it is tucked so far under the swim platform with almost zero overhead clearance. The worst part of pulling the motor will be the stupid 500 lb. if it's and ounce fiberglass rear seating/engine hatch. Thing is a cumbersome beast!

If you are 100% confident it is from the back of the motor, take the belt off and fire it up without the drive on and see if the noise is still there. You won't hurt the water pump that way.

You wont hurt the water pump running if for a few seconds with the water pump hooked up,

Other wise grab your garden hose shove it in water pick-up hole where your drive was, that will give it enough water to idle off of.

My guess is hub adapter just weird that it was fine one second not the other.

Thought about cutting the male end off my hose and shoving it into the water pickup hose but just ran out of steam on Saturday. As donzi matt stated above, I could also just take the belt off. Sometimes the obvious eludes me which is why I need you guys to help me out! :ernaehrung004:

If you have a cell phone with a camera you can reach down and take a bunch pics from different angles, maybe see something that way.

Just seen this, funny you guys throw my name in the mix.

Here is what I would do -

You can take off the inlet or unhook the water inlet cooling hose and hose clamp a water garden hose inside that inlet hose. Turn water supply on and start engine ASAP make sure it pumps water. Of course leave Serp. belt on.

Or take off inlet coolling hose back side of water pump housing and buy a 3 feet to ??? however long hose to connect to back side of inlet water pump impeller housing and either adapt a garden hose inside your hose that you just added or drop that hose in a full bucket of water and keep filling the bucket while engine is running to cool the engine properly..

The testing end here - the outdrive still OFF so take an engine alignment tool and stab it like you are checking alignment - how well is your alignment ??? or is it way off ? next test is leave the alignment tool in and run the engine ? How well of a perfect circle is the engine alignment tool rotation while the engine running or is the circle egg shaped pattern when engine running ?

What kind of shape is your gimbal bearing and U joints ?

have you scanned the engine and looked for available power ?

running the engine with drive off is the best way to separate the systems so you can pin point what side the noise is coming from. Drive side - or engine side.

A real quality doctor stethoscope really helps to. Use this all time even for fuel injectors while running. they can be pricey for a real good one but worth it for what I do day in and day out

Loose bolt (s) flywheel to crank???

Will have to read more posts here about whats going on but will throw this out just in case -

ignition Spark arc from either a bad spark plug wire(s) or spark plug(s) itself. or even a cracked coil (possible tower area) ? just a guess at this point

Since you turned killed switch off and cranked over engine no sound ( pulling kill switch kills spark hence no noise)

I would really look at this especially rear plugs and spark plug wires. Especially port side

Boat had developed a miss a few weeks back. 400 hours so tossed a set of plugs in and boat ran like new again. When I was in the bilge yesterday I double checked all my work from that job. All boots still seated on plugs and the oil line bracket I loosened to gain clearance to get the number 7 plug out was still properly tightened back in place. I will give this area more attention to make sure it is not a spark noise but when I was in the bilge laying in the port side I didn't notice any arcing. The noise more resembles a rod knock than a miss/arcing wire. Best I can tell it is coming from engine centerline back towards inner transom plate.

Truer words ,and all that !

Just something else to throw into the mix . A few years back I had an alignment problem (from new install) that didn't manifest itself until about 60 hours (a 502) .
With the hatch down and idling it would come and go and sounded like someone dragging anchor chain up onto the deck of a tin boat. The coupler went shortly after that .

As stated in initial post (sorry it is a bit longwinded), alignment good, u-joints good, gimbal bearing rotates smoothly. No idea on available power as I do not have a scan tool. Thanks!

The sound you're describing sounds like an exhaust manifold gasket leak.

Funny you should mention that . A few years ago a friend with a pair of 350 Mags had a slight 'pap , pap ,pap' sound in the engine room when running . In the process of poking around and trying to locate it I smelled exhaust gas , faintly , but it was there .
Feeling around by hand I eventually felt the blowout of an exhaust manifold gasket.

^^^^ will agree with that to exhaust manifold gasket leak.

you need to run the engine with drive off to see the what happens


An alignment tool can pull in and out real easy but when engine running and alignment tool still stabbed the circle pattern will tell you a lot.

1 if rotation pattern is egged shaped - warped coupler mounting, loose coupler, even bad coupler. Loose flywheel, bad gimbal bearing.

U joints that seem butter smooth by hand rotation testing is not a 100 % determining factor that they are good. The true inspection is to pull caps off and look for scaring and needle bearings that could worn as well. Greasing U joints helps to disguises this with hand movement testing. Just went thru this as the U joints felt 100 % great by hand but internal inspection showed a different story. Scaring seen after pulling caps off. Installed brand new U joints - the noise and slight vibration I had went away completely. Just saying and not saying this is your problem but IMO has not been ruled out 100 % either. .

simple to test for exhaust leaks and blown gaskets is with a smoke machine non running engine or run the engine with a portable gas tank mixed with fresh gas and a heavy dose of 2 stroke marine oil. You Will see the smoke of the oil coming thru the gasket leaks when running the engine. Bump up rpms to keep the engine running long enough .

More info - Just saying for carb apps run engine and oil fog thru carb with trans fluid oil or marine fogging oil at around 1200 running rpms. the oil smoke will come thru any gasket leaks hence you found your leaks. Do this all the time.

A loose spark plug can make a really loud tick since it will still fire the mixture and you are getting peak cylinder pressure escaping. You did just change the plugs, checked that boots are tight, but plug could still be loose. Maybe the tow to the gas station was enough to vibrate it a little further out of the head?

Thanks BUP. Never thought about running engine with alignment tool in place. U-joints are perma-lube. I agree I need to run engine with drive off, not just turn engine over with drive off.

I've been trying to think of what the drive to town and back on trailer could have vibrated loose. Thanks for the suggestion I'll check that.

If the coupler came loose for some reason or is out of round it could be hitting where it exits the rear of the bell housing, flywheel ring gear ?

Not to harp on you but for information, homey Depot has everything you need.

1-1/4" vinyl hose, garden hose to NPT fitting, pipe bushing, hose clamps. Just fiddle with the available fittings until you find a pipe bushing that fits snugly into the hose, screw in the garden hose fitting and you're good to go. Works great with DWP lowers.

Like I said pull off water impeller housing water input hose then buy a long enough hose to reinstall and fill bucket with water then stick that hose in the bucket of water and start engine. So simple to do and barely any extra cost.

keep a garden hose with min of water on filling the bucket so your engine / impeller does not suck the bucket dry of water.

I have something similar I made with a ball valve. Use it for winterizing and running in the driveway, but my water pump is relatively easy to get to in order to swap hoses.

other advantage of pulling belt is sez for sure if it is or isn't a belt driven accessory. doubt it though. what probly caused it was one more torque of input shaft tilting drive all way up to trailer position. so most likely culprit is gonna be coupler or u-joint or front bearing on drive...

[QUOTE=dereknkathy;4357216]other advantage of pulling belt is sez for sure if it is or isn't a belt driven accessory. doubt it though. what probly caused it was one more torque of input shaft tilting drive all way up to trailer position. so most likely culprit is gonna be coupler or u


Yes, other than the ride on the trailer the only thing the boat went thru that it has not gone thru since launch this spring is the drive tilted all the way up into trailer position.

Yes, wondering if tilting drive all the way up to tow did something to the coupler/flywheel.

Never had a need for a freshwater flush...until now! Yeah, should be easy enough to fab one up. Thanks. .

Lifter? Is the sound up top?

http://33outlaw.zenfolio.com/img/s5/...41913930-3.jpg

Attaches to garden hose.

I would change the gimbal bearing while you have it apart ( you've gotten your money's worth at 400 hrs ) . Are you sure its a greaseable and not a newer sealed bearing ? Also , make sure to use new drive installation o-ring kit ( once the o-rings on yoke flatten out , yoke can spin inside inner race ) .

Yes the gimbal bearing is greasable. I've owned the boat since new and it gets greased every year. I know exactly how many pumps it takes to properly grease it on the years I don't pull the drive to grease the driveshaft splines and check alignment. U-joints are perma-lube. I probably will toss a gimbal bearing in even though this one still rolls smoothly.

Not a typical lifter noise and coming from behind the motor best I can tell. Speaking of lifter noise, anyone else pizzed that GM discontinued their EOS years ago? Man that stuff was magic for noisy lifters!

Maybe the starter nose gear is not fully retracting and clicking on the flywheel, you won't hear that just cranking it over, but you will when it starts.

Might be starter related but really doesn't sound like it. After exhausting all the obvious causes that I have the capabilities and facilities to diagnose, I gave up and took it to a shop hoping their Merc techs can quickly/accurately pinpoint the problem. Not a good time of year around here to get some shop time due to winterizations. I appreciate all the suggestions and will post an update once I hear back from the shop. If the motor has to come out, it opens up a whole other can of worms in terms of what to do in addition to fix the problem on a 400 hour engine.

BUP got it on the water supply issue. Most gardenhoses even at full blast will not match the flow of a bravo pump at idle. If possible in your case ,if you can put 4" or so of clean water in bildge and just let the pump suck it out with a hose flowing in ,should get you 2 or 3 min run time without any bad pressure/volume mismatches.just make sure dont have any junk down there that can get sucked into pump.

Government (EPA) nailed the EOS years ago. Wasn't GM's fault.

However, I believe it is back, just under a different nme and part #. I'll go do a search.