WEIRD RPM REVS ON A UNIVERSAL M18

[FOB]

The other day I was heading back into my marina, doing about 2500 RPM, when I noticed there was a fluctuate in revs… it goes from 2400 – 2600 ever second or couple seconds… this is only happening when im above 2000 RPM… has anyone ever seen this before?I have changed my fuel filter and bleed the fuel since then and the same thing is still happening… I bleed the fuel system again just to be sure there is no air in the lines... and there is none!Anyone have any idea what this can be?The boat is a Catalina 27 – 1985 with a Universal M18 engine.Thank you to any repliesFOB

 

[jviss]

More info

Is it just the tachometer that is fluctuating, or can you hear and feel the engine speed fluctuating? Is the tach signal taken off the alternator? Are the house batteries being charged when this happens, and are they nearly full, or nearly empty?

 

[Ross]

The governor is hunting but I don't know enough

about the innards of the engine to go beyond that. It can be corrected.

 

[Ross]

FOB, I was just looking at Boatdiesel.com

it seems that Kubota makes the Universal engine so if you talk to the mechanic at your local lawn and garden Kubota equipment dealer they will probably know what the fix is. This happens often in land based equipment and you can hear it for a hundred yards.

 

[FOB]

More Info

I feel the engine flucuating... im not sure what you mean JVISS when you ask is the tach signal taken off the alternator (sorry). the house batteries are always charging when this happens, this is happening both when the batteries are lower,and when they are fully charged... Thanks for all the info so far!!

 

[Jim 5757]

RPM Fluctuation

May I suggest you post your question at Torresen's site? They are THE source for Universal (& many more), but Brian & Gordon Torresen moderate what looks like a nice forum with lots of tech input. Just one favor... let us know if you find an answer! (I'm leaning towards the governor, too).Jim Ocean Gate, NJ

 

[Peter]

tranny slipping

I've had the same problem on a catalina 27 I've recently come across, though I've seen it jump above 3000 rpm, with an apparent loss of drive. I suspect it is the transmission slipping out of gear. I hold the gear selector all the way forward to keep it in gear, and I have no problem. After short sails, I've noticed it doesn't have the problem coming back into the marina. Perhaps it goes away once the transmission gets warmed up. I'm still investigating the issue myself.

 

[jviss]

Questions

I was thinking that if it didn't feel as if the engien speed was really changing, that the electric tach could be faulty, or that the belt was slipping; since most electric tachs take their signal off the alternator, if the house batts were low, causing a big load on the alternator, and the belt was slipping or"grabbing," this migh tshow up on the tach.Most likely answers were suggested - governor problem or slipping tranny.

 

[Harry]

Check your fuel lines

We had similar symptoms. After changing the filters and making sure the prop wasn't partially fouled, I checked to make sure the fuel pickup screen in the tank did not have any algae growing on it. When that was clear I checked the supply and return lines and found them being pinched, intermittently restricting fuel flow. Rerouted the lines and the engine runs great.Harry

 

[FOB]

Air in the glow plugs??

A friend of mine told me that there could be air in the glow plugs. Is this true? He said that I should try bleeding them and ensure there is no air in there. Has anyone ever heard of this? I was under the impression that once you bleed the system via the bleeder at the fuel filter that I was good to go?I have noticed a vibration since this has started to happen... the vibration comes and goes as the engine fluctuates. I noticed it more today when I was out. Maybe this might shed a little more light to pin point what the issue could be?Thank you all once again!FOB

 

[Franklin]

FOB

you're funny Glow plugs are just little small cigerette looking sodering irons. In otherwords, they are just little metal things that get hot when electricity is applied to them. No air, no fuel, no nothing goes through them but electricity. They are used to help the engine start when it's cold and they are only used in diesel engines.