Perkins 4-108 Problem

[mmckee52]

This last weekend after a non eventfull motor of about 3hr's to an anchorage for the night, we started to get underway the following morning. When I got the motor running I noticed that I didn't have any voltage output from my alternator
on the control pannel also, at this time the motor's RPM's started to surge up and down all over the place. I thought I was going to have a run away on my hand's but after about 3 min. the alternators pannel showed the correct voltage and the motor ran fine. This is the first time this has ever happened and it took me by surprise to say the least. Could the lack of 12 volts coming from the alternator have caused this? On the way back, 2hrs to our marina everything was alright. Any thought's out there? I know the first thing I need to do is check the connections on the alternator and other places, but it sure was funny (not at the time) how the motor surged and all.

Take Care,

Mike & Glinda
s/v Blue Bayou

 

[Tom Spohn]

I had a similar problem once that turned out to be a malfunctioning starter switch. Replaced it and now no problems.

 

[bobtigar]

This sounds like either an alternator or voltage regulator that is starting to fail or a short in the system. Its happened to me twice. 1st time was insulation warn on the bilge float switch wire lead. Short was because the bare wire was in the water in the bilge. 2nd time was the lead from the ol pressure sender to gauge. Wire made contact with hot exhaust manifold, burned off insulation and shorted out the oil pressure gauge. Both easy fixes. Bob

 

[Rich Stidger]

I suspect that your engine has a mechanical fuel pump, but maybe not? If it is an electric pump (original or replacement) maybe the surging is due to the voltage levels- pump cutting in and out?

Just a thought....

 

[mmckee52]

I always try to keep a positive though and use the KISS (keep it simple stupid) method. I plan to go down and check the wiring attachments and also the belt. It just sceems odd that everything ran smooth just the day before. Ahhhh boats don't you love them, especially when there giving you problems 15 miles from your marina and the weather prediction is for 25 to 32 mph winds and rain.

Keep the ideas coming,

Mike & Glinda

 

[Bill Roosa]

surge question

I have an idea but want to make sure I understand your problem. Did the RPM of the engine surge or did the tach indicate a surge?

Not trying to insult your post but after diagnosing lots of auto engines I have learned that what the customer says is not always interpreted by the mechanic correctly.

 

[mmckee52]

Bill & Rich,
To answer both of your questions at once. The engine was surging while I was down below trying to figure out why the alternator wasn't showing any output, so I can't say what the guage was doing and yes I do have an electric fuel pump. As always on a boat one thing almost always leads to another problem area. I really appreashate all of the input.

Mike & Glinda

 

[sailaway78]

My thoughts

Your problem is a result of either the alternator or regulator trying to die, or a short somewhere. I would really suspect the latter, as it would seem that the battery should run the fuel pump just fine for a pretty good while. It is highly possible that you have a bad connection or a short or broken wire, at or near the switch. This would cut out the field voltage to the alternator and power to the fuel pump, accounting for both problems.

 

[mmckee52]

As soon as I noticed I had good water flowing my next spot to check is the oil pressure guage, it takes about 20 sec to regester a pressure reading, but after about 30 sec I got worried and thats when I went below to check things out. The engine was at idle in neutral and when I saw that the alternator volt meter showed zero output the engine started to surge faster than idle and then it started to go surge slower than idle. All & all I've got to get down to the boat and trouble shoot all of the great ideas everyone has given.

Thanks,

Mike & Glinda

 

[Bill Roosa]

dito Nice-n-easy

Well it is unlikely that all your gages went down at the same time. So I'm thinking a connector has come loose. I'm with Nice-n-easy the sysmtoms of surge and no alternator output looks like the connector that handles both the engine electric fuel pump and the alternator regulator power supply has some problems or the ignition switch is acting up.

As most Hunter owners already know the major cause of electrical and some mechanical problems is the connectors going bad.

 

[mmckee52]

Bill,
I am with you as I said in the beginning using the KISS rule. I really try to elimate the most likley area's where the problem might be first. Although everyone of the great answers that I've gotten have been very helpfull, they gave me other area's that I hadn't considered.

Thanks,

Mike & Glinda