Help Diagnosing Engine Bay Smoke
 

Hi all,

I'm in need of some advice that will let me sleep decent through the night. I just bought a new boat (very nice to me) that has been in the water 2 times in 3 years. It has had very good maintenance and has 204 hours on it. After a good check of fluids and warm up procedure on the hose in the driveway (new impeller) I thought she was ready for a sea trial. Left the dock on a slow idle watching all of the gauges for 10 minutes or so. Throttled up on a plan and let her run at 30 MPH while continuing to watch the vitals. I didn't make it a 1/4 mile and I started to smell smoke similar to burnt rubber or grease. Throttled back off a plane, shifted it in neutral and raised the engine hatch. As the hatch was going up a large amount of smoke was coming out of the engine compartment. Shut the engine off and floated for a bit trying to determine the cause. Pretty sure I shed a few tears at this point too:) I could tell the smoke was from the back of the engine area and while the boat was off I could hear a crackling sound from the input shaft area. Similar to grease crackling on a hot object. Started it back up to head for home and noticed a vibration had accured from this point on. Never smoked again on the way back to the dock but the vibration/growling sound stayed with it in all gears and in neutral. I've looked at the coupler and it doesn't seem to have shredded rubber anywhere nor does it look like it got hot at any point and the splines look fine from the outside. We are going to pull the drive this weekend in hopes that it is the gimbal bearing. Has anyone ever heard of a gimbal bearing doing this? My main goal is to be somewhat certain that it's the gimbal and not the long process of pulling the engine should it be a coupler. It's a 502 Mag with Bravo One drive. I appreciate any advice given because I know there are many experienced people on this forum I can turn to and most of them have had their hearts drop when a similar situation has happened to them:)

Thanks,

sounds like either the gimbal or a ujoint. sounds like it sat quite a bit. I've seen nearly new bearings go bad from sitting. a little water/condensation and a little time they can grow a little rust.

Gimbal bearing or u-joints for the growling noise but neither of those will give you smoke. burnt smell and smoke is the coupler.engine may be out of alignment causing all of above.

Is there a chance that the gimbal froze up and got hot enough to cook all of the grease making the smoke described? There's just two things that don't add up to me. 1) The crackling sound (almost like a cooking bacon sound but slower crackles) coming from the input shaft area after the boat was off for a while. 2) No small rubber pieces in the hull or signs of coupler getting hot when looking at it. Another thought, I lost no propulsion when the smoke hit or when driving back to the dock. I've heard if you smoke a coupler it's similar to a transmission slip. I guess I'm just trying to live the pipe dream and hope it's not the coupler. I will keep you updated as we tear it further apart. I'm a glass full kind of guy so I still have hope since a few people think it could be the u-joint/gimbal. Thanks for the replys so far.

Well growling specially when you turn is probably the gimbal, needs grease or replaced, and sometimes they just growl. was the boat stored before you bought it because people store engines in a million different way, they fog the carbs, put a cap full of oil on top of pistons, WD-40 things to prevent rust, or just flat out lube the hell out of. Let it run in your driveway and watch it, double check all fluids and grease nipples. I mean if the boat sat for three years, its probably going to burn off some crap and vibrate and growl a little bit

Oh and grease the prop shaft and anything else that has a grease zook on the lower unit

It definitely growls when you turn it. When running on the hose in the driveway in neutral it growls the most with the outdrive straight forward. If you turn it hard to the left it goes away completely and hard to the right makes it growl about the same as straight forward. The growling goes from very noticeable to completely quiet depending on the outdrive direction. Haven't seen what it does tilted up or down because by this point I knew something bad was happening and didn't want to run it longer than absolutely needed in fear of making things worse.

OK I have another problem. Either the bearing is welded on the input shaft, rusted on the shaft or the coupler is binding it on. The outdrive will not break loose and pull out. Any suggestions?

worst case: open up the top of the drive, loosen the nut so you can take the drive shaft out of the drive, pull the engine out with the drive shaft stuck in the coupler, and go from there...

that is only if it does not (the drive) pull out!

Driveshaft will not pull out with engine, it will not pass gimbal bearing.

All six nuts are off or I should say four of them. Left the last two nuts on with only a couple of threads just incase the outdrive gods granted my wish and it broke free. I can clearly see it has separated. The bottom seem has about 1/4" gap and the top of the seem has about 1/32" gap. If tried squirting penatrating oil in the coupler and gimbal. Had a partner bump the starter a few times to see if that would help. Tried pulling on the top of drive with a piece of wood at the same time. I'm down to building a jig that will put pulling pressure on the drive as I try to tap it with a hammer. Open to any and all suggestions:) The weather has just recently changed to beautiful and the longer it stays that way the more frustrated I become:)

Good news, got the outdrive off with some advice on another thread. Used the tilt cylinders and a block of wood between the top of the outdrive and the gimbal ring. Just bumped the tilt a little bit at a time then went back and rocked it back and forth and kept repeating this cycle until she broke free. Had water in the bellow and the gimbal bearing rusted right onto the input shaft. Needles to say I don't have to worry about pulling the gimbal bearing because it came out with the drive. Just need to get it off the shaft now:) The teeth look great on the input shaft and coupler. Hoping it didn't damage the coupler or throw it out of wack somehow. A few more hundie and couple more nights of working on her and we should be back out in the sunshine. The beer sure tastes a lot different at the end of a project than the do at the begining. I can finally get a good nights sleep. Thanks everybody on this website for your help. I will keep you posted. Maybe my next thread will be something a little better like how to throw down some better numbers on a pass:)

Thanks again.......

Have a final update:

After drive was pulled noticed coupler had a pretty good wobble to it. You could actually watch the alignment tool (ITS) touch the inside of the gimbal bearing the entire time the engine was rotating. It looked like 1/4" out of round in reference to the gimbal. Pulled the engine and put a new coupler on, parts houses don't give those away either:) Did have to tweak the engine a little to the port side (1/4") to get it to center on the gimbal. I didn't think the rear engine mounts would give me any play due to design but it did give me what I needed. Anyway, long story short she is all buttoned up with new coupler, gimbal bearing, seal, bellows and no more Y-pipe which makes things in the back much better to access. She runs great so far and am very happy to have had a great knowledge base like this forum to help me:)

Thank you..........

I would just take it for another slow run. If the boat has sat its going to burn off some grease and oil. Whoever stored it last might have sprayed down the engine with oil. I mean everytime i leave something for just the winter it smokes and spits and rumbles. re-grease everything, Wd-40 some moving parts. Dont forget alll the grease points on the lower unit. Sounds like she may need just a good run