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Discussion Starter #1
I have a 1987 Catalina 30 with a 275 hour Universal M25xp. The boat is kept in the SFO bay area where I work, though I live out of state. I’ve owned the boat for three years now, though have rarely used it as I’ve been (very) slowly getting the engine squared away. I just got to the point where I feel good about running it. This evening it fired up instantly, but after about a minute at idle it made what at first sounded like a rattle as if it was shaking against something in the engine compartment. Over the next few minutes the noise drastically increased in frequency. I took a video just before shutting it down. I have only run this engine a couple hours since I have owned it, but it has never had this problem until now. I understand that a super low time engine is probably worse off than a well used, high time engine, but I also know that these engines have a reputation for being very durable. I’m not sure where to go from here and I’m hoping that someone has some advice on how to proceed.

 

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Random guesses.....

dampening plate

stuck valve/lifter

bearings

water pump
 
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Learning the HARD way...
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Agree with @Minnewaska about damper plate (I once saw one of these explode, and the damage was awful). If it is fix it ASAP.

Could also be something on the exhaust riser.

Other possibility (based on the sound to my ear) is the air cleaner may be vibrating.

Disagree about a bearing or valve.
 
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Discussion Starter #4
Thanks for the suggestions guys. I realized this evening that when I refreshed the heat exchanger recently I never clamped it down on the mounting cradle since I wanted to leak test it first (somehow the radiator shop couldn’t do that). Though that isn’t the problem, I did get a little more insight. The rattle isn’t there just after start, only after running a few minutes.

A little background on this engine. I believe it is original, and fairly low time at 275 hours. I bought the boat from the wife of its deceased owner, who didn’t know much about it, and so hired someone at the marina too sell if for her. I hired the same guy to help me sail it across the bay to its new home and after starting right up initially, it refused to do so after a couple hours sailing in sporty winds. There are a few other good stories in between here and there, but the just is; I found a lot of water and marine growth in the tank, enough to fill the racor and secondary filter and...beyond? After mentioning to the sell/sail help what I found, he mentioned that earlier (sounds like he lived on the boat for a while...) he’d accidentally filled the diesel tank with water thinking it was the fresh water, but borrowed a buddy’s fuel polishing equipment, and thought he’d gotten it all out. I thoroughly cleaned the tank, replaced the filters and added Biobor to the new fuel. The low pressure fuel pump wasn’t happy to be full of water, but once that was cleared out everything seemed to be running well. I changed the oil, flushed the coolant and had a radiator shop go through the heat exchanger. Finally i cleaned some corrosion off the wiring harness which brought my coolant temp gauge back to life, and thought I was home free. That was the test run that produced this noise. Also, the noise is produced when the engine is unloaded, i.e. transmission not in gear. I revved it as high as 1700 rpm or so, which seemed to make it worse.

Let me know if anyone has any other thoughts. I’m back in Colorado now, but when I get time to go back to the boat I’ll plan on pulling the bell housing and looking at the damper plate first.
 

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Oh, when I ran it this evening I paid special attention to the exhaust riser and air filter. I don’t believe those are the source of the problem. I may try to get a section of garden hose to try and pinpoint what section of the engine is producing the noise, but for now I’m at a loss.
 

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check the easy one first, the water pump and alternator, loosen the belt and check for play. but does sound like the dampener plate
 

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Discussion Starter #7
Good advice Overbored. The alternator belt does slap around a bit more than it probably should, it’s as good a time as any to check spec and make sure it’s right, though to my ear the sound is harsher and more metallic then a rubber belt could produce. I will start with the water pump before moving on to the damper plate. I actually have a spare pump on the boat, but like the alternator belt, I doubt my noise is being produced by anything rubber. I suppose the shaft that drives the impeller could be the problem....
 

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"Hulabaloo, post: 2051684041, member: 516100"]
Good advice Overbored. The alternator belt does slap around a bit more than it probably should, it’s as good a time as any to check spec and make sure it’s right, though to my ear the sound is harsher and more metallic then a rubber belt could produce. I will start with the water pump before moving on to the damper plate. I actually have a spare pump on the boat, but like the alternator belt, I doubt my noise is being produced by anything rubber. I suppose the shaft that drives the impeller could be the problem....
[/QUOTE]

I realize this is 11d old but he didn't mean the belt slipping would make the sound. He meant loosen the belt tension off so it's not tight on the pulleys then wiggle the pulley on the waterpump(s) by hand and alternator. Those object spin on bearings and if they go bad they make a racket before they seize or blow apart sending the pulley flying. My fresh water pump bearing went and I could hear when it started to go over the insulation of my engine bay and over the sound of my engine at 2600rpm while standing in my cockpit. All those pulleys should have no wiggle or play. If they do the bearings are failing.
 

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While perhaps not the total solution, if you have not removed the aluminum mesh from inside the Universal metal 'can' air cleaner, do so immediately. Our '88 M25XP engine developed quite a bit of blow-by, and our mechanic believed that pieces of that mesh had been ingested into the cylinders. I removed it. I stopped the "air cleaner" can from rattling with some changes to the clamping part on the base.
What lots of other owners of your engine have done is to change to a K&M filter, clamped onto the same intake tube.

As for the torque plate.... in my experience a broken spring jams and stops the rotation.... and if you're lucky that's the extent of the damage.

Best to get a good mechanic on the scene to watch and listen. (perhaps either a marine or tractor mechanic....... same Kubota engine!)
Good luck to you!
 
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Discussion Starter #10
Thanks guyfromthenorth and olson34. I still haven't been out to the boat yet as it is 1000 miles away, but I'll check out the water pump bearing and air cleaner before I get into the major mechanical stuff, and will consider removing the interior mesh of the air cleaner as well. I like doing my own MX, but may be in a position where I will be selling the boat as I won't be in CA for work for 19 months. Still in negotiations with my "director of operations" to keep it though. In any case I may have to hire pro help to get the engine resolved. I'll try to update the thread when I have an answer.
 
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