Power not revs

Canal Boat - - Back Cabin: -

TONY REPLIES... Don’t dis­miss a fuel prob­lem. The amount of fuel re­quired re­lates to the power the en­gine is de­vel­op­ing, not the revs. The power re­quired to rev an en­gine in neu­tral is very lit­tle more than at tick­over. An en­gine with a fouled prop run­ning flat out at, say, 900rpm will use more fuel than one driv­ing the boat nor­mally at 1,500 or 2,000rpm.

I as­sume you have checked your prop is clear and tried giv­ing it a mo­men­tary rev in re­verse in case fallen leaves or weed have packed into the prop disc.

As long as you have ad­e­quate oil and oil pres­sure, and there are no signs of over­heat­ing, it points to a fuel sys­tem prob­lem, but first check the gear­box oil is at the cor­rect level and nice and clean. Make sure, too, your stern gland is not run­ning hot.

Then re­place/clean all your fuel fil­ters and wa­ter traps. Drain the old ones into a tub so you can in­spect the fuel. Take the old fil­ters apart so you can in­spect what they might have caught. If the fuel is dis­coloured, there is any sign of jelly like sub­stances or there are more than a few drops of wa­ter, you have a fuel is­sue.

If you have an older en­gine such as a BMC, Perkins 4-10x, or older Lis­ter, check the strainer and wa­ter trap un­der the fuel lift­pump cap. Try blow­ing back down the sup­ply pipe into the tank in case it’s blocked. You might have an air leak in the fuel sys­tem but, as you don’t men­tion dif­fi­cult start­ing or the need to bleed the sys­tem, this is less likely.

The symp­toms might in­di­cate a faulty lift­pump but check the fil­ters first. Mit­subishibased en­gines (mainly Ve­tus and more mod­ern Thorny­croft) of­ten use a cylin­dri­cal elec­tric lift­pump with a small fil­ter un­der an end cap. These are known to cause prob­lems when they are not changed dur­ing a ser­vice. When cruis­ing, my boat loses power in­ter­mit­tently. The revs drop to­wards tick­over and then pick up again. With the en­gine in neu­tral, even when the en­gine ap­pears to be strug­gling in gear, I can im­me­di­ately rev it up to or be­yond 2,000rpm. That makes me sus­pect that the is­sue isn’t fuel-re­lated; I only lose power when in gear and it seems to hap­pen more at higher revs. I’m cur­rently on a month-long hol­i­day and if this con­tin­ues it’s go­ing to ruin it be­cause I can’t rely on the en­gine.

PLEIADES, from the CB web­site

Newspapers in English

Newspapers from UK

© PressReader. All rights reserved.