Started up the boat this afternoon and no more rough idle. I did not touch a thing. Then I noticed that as soon as I put even a slight load on the alternator the rough idle came back and I had to rev the RPM's slightly to smooth it out. Should I just advance the throttle linkage to have her idle at a slightly higher RPM or is there something else going on with the alternator? The engine is a Universal M25XP with the standard Motorola 55 Amp. I did purchase a new Leece Neville 72 AMP with Balmar MC-612 Voltage Regulator but got cold feet last year about installing it myself. Both parts are sitting under my desk as I type this. I did locate a highly recomended Marine Electrician who is willing to do the work. He just could not do it in my winter yard. The though keeps popping into my head "if it aint broke, don't touch it". Would replacing the alternator solve the "load issue" on the engine or make it worse? The only load on the alternator was my Depth, Speed and Wind along with my GPS.
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If you put the engine in gear without advancing the throttle
does it idle rough?. If yes then perhaps a turn of a screw is in order. Down on the engine there should be a stop screw that limits the movement of the linkage.
does it idle rough?. If yes then perhaps a turn of a screw is in order. Down on the engine there should be a stop screw that limits the movement of the linkage.
Not much of a load!!!
All those loads together probably don't add up to an amp. Recharging the battery after using the starter motor is a bigger load and since you just started it that load would be on the alternator. I am having trouble believing that turning on these instruments is loading up the alternator enough to cause this. The alternator could have bad bearings but that would be obvious from the low rumble but that would not go away with a slight increase in RPM If you have identified that electrical loads are causing the rough idle then a look at the voltage output is in order. See if you can correlate increased voltage (indicating charging and a load on the alternator) with the rough idle. If it was a gas engine I'd say you had some electrical interference causing a misfire but this on has me stumped.
All those loads together probably don't add up to an amp. Recharging the battery after using the starter motor is a bigger load and since you just started it that load would be on the alternator. I am having trouble believing that turning on these instruments is loading up the alternator enough to cause this. The alternator could have bad bearings but that would be obvious from the low rumble but that would not go away with a slight increase in RPM If you have identified that electrical loads are causing the rough idle then a look at the voltage output is in order. See if you can correlate increased voltage (indicating charging and a load on the alternator) with the rough idle. If it was a gas engine I'd say you had some electrical interference causing a misfire but this on has me stumped.
Alternator takes power - sometimes alot!
Chief, if your batteries are low from sitting all week, the alternator is trying to put out max current to bring your batteries up. It really does not matter that you have a light load on it. All engines will get dragged down when the alternator is kicking out current. Alternators can be a significant load to the engine. I think your alternator is OK. EDIT -- This is true if you added the load with the selector switch by bringing your batteries in and out with the load. If I go from battery 1 to battery 2 and one of the batteries are low - it will drag my engine down also.
Chief, if your batteries are low from sitting all week, the alternator is trying to put out max current to bring your batteries up. It really does not matter that you have a light load on it. All engines will get dragged down when the alternator is kicking out current. Alternators can be a significant load to the engine. I think your alternator is OK. EDIT -- This is true if you added the load with the selector switch by bringing your batteries in and out with the load. If I go from battery 1 to battery 2 and one of the batteries are low - it will drag my engine down also.
In order to ID the problem, you have to have everything in
working order so you can eliminate likely causes of trouble. You know that that Motorola 55 is not the most ideal set-up. Take some voltage readings when the engine loads up. It might be that the alternators internal regulator has failed and the alt. is putting out maximum voltage/current. Are your batteries consuming more water? The adage, "if it ain't broke...." doesn't apply to boats because it lulls you into a false sense of security. Boat problems can sometimes be manifested in a different way. If you think you have a problem, you probably do and you'd be advised to look into it before it bites you at the worst possible time.
working order so you can eliminate likely causes of trouble. You know that that Motorola 55 is not the most ideal set-up. Take some voltage readings when the engine loads up. It might be that the alternators internal regulator has failed and the alt. is putting out maximum voltage/current. Are your batteries consuming more water? The adage, "if it ain't broke...." doesn't apply to boats because it lulls you into a false sense of security. Boat problems can sometimes be manifested in a different way. If you think you have a problem, you probably do and you'd be advised to look into it before it bites you at the worst possible time.
Chief, fix one probem at at a time.
If you choose to install the other alternator, you may mix new problems with preexisting problems. If the boat ran well before the filter change, look for possible air leaks. Air leaks mostly affect low speed. When at idle, air slowly filters into the fuel system and wants to stall the engine. At speed, the pump over cdomes the air and you don't notice it's affects. Before you change any engine settings, check for air leaks! First at the filter and second where you bleed you fuel line. Once you get things the way they were, then play with the new alternator. It will be a bonus if installed under good conditions. Fix the old first, or at least know what is not working. r.w.landau
If you choose to install the other alternator, you may mix new problems with preexisting problems. If the boat ran well before the filter change, look for possible air leaks. Air leaks mostly affect low speed. When at idle, air slowly filters into the fuel system and wants to stall the engine. At speed, the pump over cdomes the air and you don't notice it's affects. Before you change any engine settings, check for air leaks! First at the filter and second where you bleed you fuel line. Once you get things the way they were, then play with the new alternator. It will be a bonus if installed under good conditions. Fix the old first, or at least know what is not working. r.w.landau
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