Gimbal Bearing vs Coupler Noise - Test Procedure

loadnet · Oct 22, 2003

1976 24 Searay 351 Mercruiser 233 hp I'm wondering which is the best way to determine what's causing a slight howling/scraping type noise - I swear - I'm begining to hear comming from the backside of my 351? when idling the engine. I'm thinking, remove the belt first to rule out pully, water pump noises traveling 'thru' the engine to the rear? Or remove the outdrive / start her up, and see if the noise is still there and IF I DO GO THIS ROUTE, can I run this engine with outdrive REMOVED, and no water hooked up for a few minutes or so just to see if the noise is still present? Thanks, PB

johnkc · Oct 22, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

captain, when you remove the drive reach in and give the gimbal bearing a turn to see if it is rough ,if it is then that is the noise. if you want to make sure though you can start the engine for a minute without the drive .but if that makes you nervous have someone hold the garden hose in the water passage in the bell hsg while you are in the boat running it .it is a lil noisy and exhaust comes out the bell hsg.so whoever holds the hose has to be brave,there feet may get wet also.good luck !

loadnet · Oct 22, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Thanks.. JohnKC Is the noise I'm describing sound like what 'could be' a gimbal bearing to you, or??

johnkc · Oct 22, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

yupp,most likely gimbal bearing.

loadnet · Oct 22, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Thanks JKC Appreciate the quick response!

affa · Oct 22, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Hello I read here somewhere that the noise would become stronger if you turn the steering full to one side if it was a bad bearing Affa

djvan · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

My bad gimble bearing sounded like a low "grumbling" noise. Almost like when a 4wd truck is in 4wd (if you have a 4wd you'll know what I mean). DougV>

loadnet · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

I've turned the outdrive full starboard and full to port IN and OUT of the water, and the noise does NOT increase. It may be that the bearing wear is in it's very early stages. My ears don't miss a trick when it comes to my engine sounds... and I just know, I hear something different going on behind the engine. If ya stick your head down behind the engine (at idle) the noise is a little more evident. Like a faint howling, or scraping noise almost. I've had the boat out a good number of times since first hearing the noise and it hasn't seemed to get any worse at all, which is weird? Guess I'll yank the Outdrive and make believe I'm a Proctoligist.

llerrad · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Don't forget to check the coupling on the flywheel could be a worn rubber bushing.

tylerin · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

CaptainHF, I'm not sure what your looking for by running w/out drive. The gimbal won't be turning and you won't hear anything from your coupler w/out the spline shaft sticking in her. Is there another noise your looking for?

loadnet · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

No matter what I do right now I can't really zero in on the noise...so I'm thinking if I yank the drive and fire her up and the noise goes away at least that rules out the engine all together, except for the coupling of coarse.. Now If I reach in behind the engine, how will I know if the coupler bushing is shot? Will there be movement side to side or something on it? I know I'll be checking out the gimbal to see if it turns rough, or feels like the race is rough, but the coupler I'm not really sure the best way to test if it's wiped out or not. I've been running the boat 3 times a week over here so the noise is very faint. I'm trying to jump on this weird development before it causes a 'real' problem down the line.

tylerin · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

I've never had a coupler go out but what I gather is Rubber smell-coupler coming apart Overheat problems-engine not turning impeller Rpms rising and no mph gain. These are symptoms. Couplers don't make noises they either work or they don't

tylerin · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

By the way CaptHF, If and when you pull drive get your hands on an alignment tool (a must to reinstall drive). Poor engine alignment is probably the #1 cause of coupler problems

loadnet · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

..with all that in mind I believe I do not have a coupler issue, because the engine was aleigned perfectly when the outdrive was last installed, and no rpm rise problems, or smell of rubber anytime at all. Probably just the gimbal on it's way out the door. OK thanks for all the scoop. I'm all set now with the info you've provided me. Take care,

tylerin · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Check your u-joints while you have the drive out. Grease em up

loadnet · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

Yup!... that's on my "Things To Do" List for sure. Thanks!

Destin · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

I had a high pitched squeaking noise, sort of like eek-eek-eek, coming from the back of the engine that I could only hear at idle. When I pulled the Alpha1 outdrive, I had gear lube in the bellows. Turns out the oil seal on the input drive gear had worn thru the rubber, and the little steel compression spring was cutting a groove in the drive gear. My mechanic said he almost had to replace the gear, but he was able to use a special service seal to bypass the damaged area. He also told me that Mercruiser had a service bulletin not to use any synthetic HP Gear Lube, because that had caused problems with failing oil seals. I have never found any information to support that.

loadnet · Oct 23, 2003

Re: Gimbal Bearing vs Coupler Noise - Test Procedure

..thank you for that info. I do believe I have a gimbal bearing worn but not anywhere near needing replacement, however I'm ripping it out and replacing if I just feel the least little bit of roughness when I stick my hand in the gimbal housing and turn it back and forth.. Don't want anything seizing up on me when I'm 10 to 20 miles out into the ocean. Doesn't sit too well with me.

Gimbal Bearing vs Coupler Noise - Test Procedure

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