Impatient Engine...?

[boatone]

Have had three overnights on the old lady already this season.......brill weather!
Havent even got round to changing oil, filters etc so far but boat behaving well with one small oddity .
Cruising along happily with both engines around 1500 rpm or so(non tidal thames so river speed).
Suddenly, starb'd engine will increase revs by about 300rpm for a few seconds (15 secs or so) and then drop back to 1500 or whatever. Can do this on and off about every 15 - 30 mins or not do it at all for ages.
Any ideas, stupid suggestions, factual analysis or what have you gratefully received.
TonyR

<hr width=100% size=1><A target="_blank" HREF=http://www.boatsontheweb.com/galleryframes.html> BoatsOnTheWeb, Photo Gallery, Chat Room</A>

 

[DavidJ]

I think diesel pumps work on a speed regulation principle (as opposed to a petrol carb which just sucks it in) so I suspect the regulator mechanism sticking a little. Might get away with some diesel lubricant additive...worth a try
David

<hr width=100% size=1>

 

[jleaworthy]

Air in the fuel lines to stb'd engine. As air passes through governor, governor increases fuel supply and so increases revs. You'll need to bleed lines and find where air is being drawn in - probably somewhere between tank and lift pump. Try tightening all unions as a first step. Good luck.

<hr width=100% size=1>

 

[boatmad2]

Could be any of the following in any order.
Fuel filter partly blocked, weak lift pump, slight air leak somewhere, alternator regulator switching on and off,internal fault in injector pump, partly blocked air filter, water droplets in fuel, incorrectly set antistall regulator on injector pump, movement of engine on mountings pulling on throttle cable. Soz can't think of any more.

<hr width=100% size=1>

 

[mad_boater]

I have the same problem with one of my engines. If you have the old style inline diesil injector pump that needs topping up with engine oil every now and again this could be your problem. The pump needs oil to damp it or it will "hunt" ie.the revs will go up and down. Usually there is a screw for filling it (quite large) on the top of the pump and another half way up the side (small ) to open as a level , when you put the oil in the correct level will be achieved when it trickles from the side screw. Hope this does the trick.

<hr width=100% size=1>

 

[Chris_B4]

I had a similar problem when I took delivery of my boat, engine rpm varied by about 200 rpm or so. It turned out to be air getting in as jleaworthy suggests and was sorted by checking that all the unions were secure

<hr width=100% size=1>

 

[BarryH]

Oh right I see, don't trust me huh! Well everyone else has said what I said........not gonna let you play wiv my tools now!

<hr width=100% size=1>

 

[duncan]

Re: Impatient BarryH(nm)

<hr width=100% size=1>