Nate 2 Posted January 24, 2016 Share Posted January 24, 2016 A mates Volvo 20 something in his cruising yacht is making a screeching sound and losing power at 1400 revs. Any thoughts on where to start? He is out in the gulf with his family and wondering if he should come back. Quote Link to post Share on other sites
The big T 40 Posted January 24, 2016 Share Posted January 24, 2016 Loose fanbelt? Doesn't explain loss of power though. Quote Link to post Share on other sites
Island Time 1,225 Posted January 24, 2016 Share Posted January 24, 2016 Sorry, not enough info. Screeching is BAD. Likely metal on metal. Where to start. Is there any oil in it? What does the temp gauge say? Is there water coming out the exhaust? Is there any water in it (closed circuit cooling) ? Have a look for the source of the sound. Is the sound from the alternator, water pump, turbo (if fitted, prob not on a 20 odd HP), gearbox, shaft where it goes thru the hull etc? Does it do it in gear and out of gear? Do you mean by power loss that it will not exceed 1400 rpm? If so, is that the same in and out of gear? This could be a simple bearing failure on an accessory, or the stuffing box cooling, right through to run main or big ends, requiring a motor replacement/rebuild.... Cannot say at this point. But yes - if the source cannot be located - STOP USING THE ENGINE! at least until identified... Quote Link to post Share on other sites
Island Time 1,225 Posted January 24, 2016 Share Posted January 24, 2016 if it's a belt slipping or a bearing, then using a long screwdriver on the offending part and your ear on the handle end, you will quickly locate the source. Be careful and don't catch it in any moving parts! Quote Link to post Share on other sites
Nate 2 Posted January 24, 2016 Author Share Posted January 24, 2016 Thanks, I will pass this on. Apparently noise starts at 1400 and revs drop to 1100 and can't be coaxed back up. Quote Link to post Share on other sites
Farrari 4 Posted January 25, 2016 Share Posted January 25, 2016 Does it make this sound when it's not in gear? My saildrive made screeching noises and resulted in loss of power when the SD rear shaft seal started to fail. Water was found in the SD oil (Oil was a white murky colour when you pulled the SD dipstick out). Quote Link to post Share on other sites
Island Time 1,225 Posted January 25, 2016 Share Posted January 25, 2016 Water is often found in SD gear casing oil. Not immediately a problem, but will be if it is left.... That is why it is good to check the levels and condition at least weekly! Caught early it's usually a cheap oil seal and some new oil. Left it can lead to a rebuild or new saildrive A "screeching" sound is often a stuffed bearing, bush, or possibly a seal. A seal would not explain the revs restriction in this case. A bearing or a bush failed is the likely cause - a 20 hp motor does not take a heap to stop. Works like this - the bearing/bush is ok until it gets hot (in this case around 1400 rpm under load) then the additional load it creates by binding restricts the revs to 1100. If ignored, it could seize completely which will likely have consequential damage. That would be my guess at this point. This issue could be the in/on the engine, gearbox or drive. If a shaft drive, check the shaft strut for obstructions - a fishing line in the cutlass bearing can do this, and the noise will be loudest with the screwdriver test (see my post above) just above the cutlass bearing mounts inside the hull.... And of course it won't do it out of gear! Awaiting further info.... Quote Link to post Share on other sites
wheels 543 Posted January 25, 2016 Share Posted January 25, 2016 It will be interesting to know the result. I can't really add anything more to the great info already posted, apart from that it sounds serious. I would suggest he doesn't need to come home early. the damage is done by the sound and coming home in a week or two or today is not going to make a lot of difference.The only other thing I can think of, doubt but hey it's possible and it's a little engine, and that is if the ALT bearings have failed and the squeal is the belt driving it. That needs to be checked because failure of the belt due to an ALT seizing will cause the engine to over heat from lose of the engine cooling pump being driven. Quote Link to post Share on other sites
Marshy 30 Posted January 25, 2016 Share Posted January 25, 2016 Yeah thats not a bad suggestion Wheels. Alternator bearing would squeel and can load the engine up hard. A few questions also - when it wont rev out: 1) Does it black smoke? (As if the fuel system is trying to fuel it but its overloaded) 2) Will it rev out in nuetral - eliminating the sail drive, or shaft / gearbox systems as faults. Quote Link to post Share on other sites
Nate 2 Posted January 25, 2016 Author Share Posted January 25, 2016 Thanks for all the feedback. He bought it back in yesterday and managed to get someone to take a look at it. Turns out it was an incorrectly sized alternator belt making all the noise, and the tachometer running off the alternator giving the impression the revs were dropping. Quick fix and back out. Quote Link to post Share on other sites
Island Time 1,225 Posted January 25, 2016 Share Posted January 25, 2016 All good. Time for a basic diesel Maint course I think! Pretty easy fix that should have been able to be easily diagnosed without returning, and the SPARE belt fitted. There was a spare, right? Quote Link to post Share on other sites
too_tall 15 Posted January 25, 2016 Share Posted January 25, 2016 I hope the owner of this boat is a good sailor and looks after his vital components better than he understands his engine. He sounds likely to have sailing into his berth/onto his mooring as a common feature of his future sailing exploits. That squealing should have been very obvious, corrected very quickly, and really, never have happened. Belt squeal is quite a distinct sound. IT.. spares? What are those? I think we carried 6 spare belts for the alternators to Tonga last year!. @ $90 each, thats a considerable investment. Needed 2 of them though ( poor installation of A series belts on 90 amp alternators equals belt eating ). Fixed installation now though. Twin belts, screw tensioner. All good Quote Link to post Share on other sites
Island Time 1,225 Posted January 26, 2016 Share Posted January 26, 2016 Yep TT Agreed. Poor belt alignment is a pretty common problem, especially with retrofitted alts. Many underestimate the loads they bear, and although ok for a few hours around the Gulf, they are not up to continuos duty. Lots of black dust in the engine room, esp near the belts is a real giveaway! Quote Link to post Share on other sites
wheels 543 Posted January 26, 2016 Share Posted January 26, 2016 It is easy for some of us more mechanical minded to wonder how on earth others can't see the simple. But having taught many challenged in the mechanical nous department, I have had to realize that to some, mechanical issues are like me trying to translate French when it is spoken in German by a Russian. Quote Link to post Share on other sites
wheels 543 Posted January 26, 2016 Share Posted January 26, 2016 Actually that brings up a slight side track to the thread, but seeing as the problem is solved.Who has ever tried to change their car tyre lately? Most importantly to this question, "if your wheels have been fitted at a Tyre Shop! I had this happen to me and am now finding it a common complaint. These shops re using rattle guns to tighten the wheel nuts. Just try removing a nut with a wheel brace after it has been tightened with a rattle gun. It is impossible. In fact, I completely bent one brace and I broke another. I ended up with a good Socket and power bar and a length of pipe and then I had to jump on it. There is absolutely no way I could do this on the side of the road. I have had several others give similar stories. Which then brought us to a conclusion, that seeing as we can no longer change our tyres ourselves on the road side, why should we have to carry a spare, jack and other gear in the boot, which is required for WOF by the way Quote Link to post Share on other sites
erice 732 Posted January 26, 2016 Share Posted January 26, 2016 have seen the better tyre shops use a torque wrench but have seen others wail away with the rattle gun and when asked what they were doing told "DONT WAN THE NUTS COMING OFF DO YA!" as well as difficult to remove without special tooling over-tightening can/will eventually lead to snapped off studs which can lead to the loss of the wheel and an accident Quote Link to post Share on other sites
too_tall 15 Posted January 26, 2016 Share Posted January 26, 2016 I would be pretty unlikely to be happy if I saw wheel nuts being tightened to the max a rattle gun with 150psi up its date will do. I actually go to a commercial shop, and they only ever use torque wrenches. In fact, they have a little computer whereby they tap in the rego and it tells them what torque to use. I guess that not a lot do that unfortunately. That being said, no wheel nut has ever bettered me. Not even truck ones. But they get done with a 1" socket set and a big maul.... Quote Link to post Share on other sites
wheels 543 Posted January 26, 2016 Share Posted January 26, 2016 The nuts I had problem with were after Mag and Turbo in Genfield had fitted the wheels.The torque required for most cars is not actually that much. Most cars are on average, from 70ft-lbs to 90ft-lbs. If you are not sure, 80ft-lbs will get you by in most instances. It is not hard to apply 80 with a cross wrench. A good rule of thumb is the following. Remember this for your Boat trailer. 10mm stud 50 ft-lbs 12mm stud 100 ft-lbs 14mm stud 120 ft-lbs 4WD studs can need a little grunt. They tend to range from 100 to 120 for most and those newer really big machines like the Ram and F250 etc can be as much as about 150ft-lbs Quote Link to post Share on other sites
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