Slight knock at idle / 1995 OMC

[Shade Tree boy]

Hello,

I purchased a 1995 Four Winns with an OMC 4.3 GL and cobra sterndrive earlier this year. I have noticed on a few occasions a low volume knock coming from the stern area of the boat. I dont think it's an engine knock. It seems to go away or become much less pronounced after the engine and sterndrive have reached operating temperature. I noticed it more than ever the other day as I was flushing the engine for winterization. Everything was cold except the engine, since it had been sitting in the driveway for a few weeks. I ran the engine up to normal operating temps and the knock seemed louder than before. Certainly louder than when it's in the water. Another detail is that I don't hear the knock if I'm outside the boat. I would appreciate any and all comments, guesses, and troubleshooting ideas. I would like to solve this issue this winter, so I can have a trouble free summer. Thanks!!

 

[Black as]

Re: Slight knock at idle / 1995 OMC

I had the same thing when I purchased my boat but I have a V8 and found that my idle was to low, not sure if that's your issue but just a thought anyway.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

Good thought Officer Black as. I'm glad no one is throwing out serious problems....yet. I will definitely look into this.

 

[sea wolf]

Re: Slight knock at idle / 1995 OMC

Hello,

I purchased a 1995 Four Winns with an OMC 4.3 GL and cobra sterndrive earlier this year. I have noticed on a few occasions a low volume knock coming from the stern area of the boat. I dont think it's an engine knock. It seems to go away or become much less pronounced after the engine and sterndrive have reached operating temperature. I noticed it more than ever the other day as I was flushing the engine for winterization. Everything was cold except the engine, since it had been sitting in the driveway for a few weeks. I ran the engine up to normal operating temps and the knock seemed louder than before. Certainly louder than when it's in the water. Another detail is that I don't hear the knock if I'm outside the boat. I would appreciate any and all comments, guesses, and troubleshooting ideas. I would like to solve this issue this winter, so I can have a trouble free summer. Thanks!!

If the knock is coming from the stern drive, then it may be u-joints. You'll have to pull the drive & inspect them. You won't hear the knock when the boat is in the water as the drive is submerged. When's the last time they were greased?

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

It's hard to say when they were greased last. The guy I bought it from had it for 4 years and I doubt he pulled the drive. The u-joints would make sense. Could it be the gimbal bearing? I am comfortable pulling the drive and greasing or even replacing the u-joints and gimbal bearing. My concern is the engine alignment portion of the job. What is that about? My manual says i need a special tool but it's not as descriptive as I would like for it to be. Is this a big job, or something a shade tree boy could handle?

 

[sethjon]

Re: Slight knock at idle / 1995 OMC

You could handle it with very little problem. Its a metal tube if you will, that fits into the engine with the OD off and when it slides in easily you're aligned. Sometimes getting to that point is a PITA but not rocket science. The tool should cost about 50-60 dollars.

 

[stackz]

Re: Slight knock at idle / 1995 OMC

tool is cheap on ebay most of the time. frisco made one himself if I remember correctly.

are you able to get your head next to the engine when its making the noise to see if its coming from the drive or the engine?

 

[sea wolf]

Re: Slight knock at idle / 1995 OMC

It's hard to say when they were greased last. The guy I bought it from had it for 4 years and I doubt he pulled the drive. The u-joints would make sense. Could it be the gimbal bearing? I am comfortable pulling the drive and greasing or even replacing the u-joints and gimbal bearing. My concern is the engine alignment portion of the job. What is that about? My manual says i need a special tool but it's not as descriptive as I would like for it to be. Is this a big job, or something a shade tree boy could handle?

If the drive hasen't been off in 4 yrs., then it's long overdue. The gimbal bearing will usually make a growling noise when it's shot or it will feel rough when u spin it by hand. I'd pull the drive, inspect everything & go from there.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

Thanks for all the comments. I must say I am a little intimidated by the thought of pulling the out drive. My concern is not my ability to put it all back together, but more about the things I don't know. "You don't know what you don't know" kind of thing. The last thing I want is to get something wrong and cause additional damage. Besides checking the engine alignment, is there anything else I need to know?? Thanks again for all the great input!!

 

[DBreskin]

Re: Slight knock at idle / 1995 OMC

Thanks for all the comments. I must say I am a little intimidated by the thought of pulling the out drive. My concern is not my ability to put it all back together, but more about the things I don't know. "You don't know what you don't know" kind of thing. The last thing I want is to get something wrong and cause additional damage. Besides checking the engine alignment, is there anything else I need to know?? Thanks again for all the great input!!

If you have a manual, even a Seloc manual, It's easy to learn to pull and replace the outdrive (assuming you don't run into anything needing repair.) After you've done it once, you can do it in 5 minutes or less. Reinstalling takes only slightly longer if the drive is aligned.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

OK...so I have purchased an alignment tool off ebay. From all the other threads on here it appears that alignment tools are all pretty standard and even interchangeable between volvo/penta and mercruiser. My concern is that my manual calls out a different omc part number for the alignment tool on my 1995 omc than it does for the 1993 and earlir models. Does this mean that the tool is dimensionally different? It also talks about a "splined" end of the tool, but my tool and all the sketches of these tools that I have come across do not have splines. Can some one clarify if the tool I have will work on ALL Omc sterndrives, and does the end have to be splined?

 

[bruceb58]

Re: Slight knock at idle / 1995 OMC

Your tool is fine. The tool should not have splines.

More than likely the part number changed when the joint venture between Volvo and OMC occurred.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

Excellent input everyone. I successfully finished the project this past weekend. It was surprisingly easy. The only difficult part was getting the drive back on. Getting the u-joint drive shaft through the gimbal bearing and then into the engine coupler took longer than the whole job. The u-joints looked great although certainly needed new grease. The grease that was pushed out still looked ok. She is greased to the max now!! The Gimbal bearing had a very smooth feel and action to it, and there was absolutely no play in the bearing whatsoever. I replaced the rubber o-rings as well as the water sealing seal. Another interesting detail was that when I started to grease the spider component of the u-joints I couldn't find the zerk fitting on one of the spiders. After closer inspection I noticed a hole in the spider where I suspected the zerk fitting should be. I started to fish around inside the bellows, which by the way had a pool of gear oil it. In the pool of gear oil I found the missing zerk fitting. The threads were damaged on the zerk fitting so I replaced it with a new one. I was surprised to find gear oil in the bellows. Is this normal?

 

[Bridar]

Re: Slight knock at idle / 1995 OMC

I was surprised to find gear oil in the bellows. Is this normal?

It's not unusual, but its a sign of a leaky seal.

 

[cr2k]

Re: Slight knock at idle / 1995 OMC

Leaky upper seal on your outdrive. Check your drive for water in the oil. You did use a good Spline grease on the splines? Doesn't take long to ruin a coupler.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

When I changed the stern drive gear lube and there was no evidence of water in the gear lube. On the contrary the lube looked very good. There were no metal filings either. I used moly grease, as per my manual, on the drive shaft splines before re-assemble. I did notice, however, that the lower gear lube was overfilled before I changed it. Could over filling the gear case force the leakage?? All the seals and components appeared to be in great shape.

 

[Shade Tree boy]

Re: Slight knock at idle / 1995 OMC

OK...so spring like weather has finally arrived in middle TN, so I made the test drive yesterday. Whew...that was a long time to wait and wonder if it worked, and whether or not I screwed something up. THE KNOCK IS GONE!! Everything ran, and shifted flawlessly. She is ready to burn up some 4 dollar a gallon gasoline.