Pre­pare your diesel for the sail­ing sea­son be­fore launch day

SAIL - - Contents -

My wife, Ter­rie, and I laid up our Malo 47, Nada, ashore in Spain this past Au­gust and came home to take care of other busi­ness. We will be re­turn­ing to Nada to­ward the end of this month. All sys­tems were work­ing fine when we left, but it can­not be pre­sumed this will be the case when we go back. Me­chan­i­cal things need reg­u­lar use and tend to seize up with­out it. Me­chan­i­cal and elec­tri­cal equip­ment also both suf­fer from the salt at­mos­phere in­vari­ably present along any coast.

There is al­ways an el­e­ment of trep­i­da­tion when I step on board the boat af­ter a long layup and turn on the main bat­tery switch. Will the panel come alive, or are the bat­ter­ies dead? Af­ter that, as­sum­ing the elec­tri­cal sys­tem boots up as it should (and fol­low­ing a mo­ment of bliss­ful re­lief !) there are also a num­ber of tests I run both be­fore and af­ter I’ve fired up the en­gine to help en­sure things go well in the months to come.


The Holy Trin­ity for diesel en­gines is clean fuel, an un­ob­structed air­flow through the en­gine and ex­haust and com­pres­sion lev­els that re­sult in high enough air tem­per­a­tures to ig­nite the in­jected diesel fuel. In what fol­lows, I am go­ing to as­sume read­ers have been dili­gent about rou­tine main­te­nance. Even so, the #1 cause of prob­lems with marine diesel en­gines is con­tam­i­nated fuel. Over a win­ter layup, es­pe­cially with a metal tank that is not full, there will be con­den­sa­tion on the tank walls that will re­sult in a small pool of wa­ter in the base of the tank. This must be re­moved rather than wait­ing for it to be col­lected in the pri­mary fuel fil­ter.

CLEAN FUEL: On all the boats we’ve owned over the past 30 years, I have in­stalled a pumpout line set to within an eighth of an inch of the low­est point in the tank and con­nected to ei­ther a 12-volt diesel fuel pump—avail­able from any au­to­mo­tive store—or a man­ual pump rated for diesel. I al­ways pump a sam­ple of fuel from the base of the tank be­fore crank­ing the en­gine at the be­gin­ning of the sea­son, as well as af­ter re­fu­el­ing and through­out the sea­son it­self. In re­cent years I have also added yet an­other line of de­fense again wa­ter in­tru­sion in the form of a hy­gro­scopic (mois­ture ab­sorb­ing) fil­ter on my fuel tank breather from H2Out.

In ad­di­tion to wa­ter, this sam­pling line will also re­veal the pres­ence of any other fuel con­tam­i­na­tion that might ex­ists. Many read­ers, es­pe­cially those with older boats, will have se­ri­ously fouled fuel tanks. All of us are also go­ing to be faced with an in­creas­ing po­ten­tial for bac­te­rial foul­ing in fu­ture as we find bio-diesel creep­ing into our fuel sup­plies.

If foul­ing is found, the sin­gle most im­por­tant fa­vor you can do your­self is to find a way to get into the tank and clean it up—as soon a pos­si­ble! This is vi­tal if you want a re­li­able diesel en­gine. The cleanup is typ­i­cally not easy, as I know from ex­pe­ri­ence af­ter we had to do it on our own boat af­ter tak­ing on a batch of se­ri­ously con­tam­i­nated biodiesel in Swe­den. On the plus side, how­ever, it’s less trou­ble than hav­ing your en­gine conk out when you most

need it, like when you’re claw­ing your way off a lee shore.

AIR­FLOW: Once I’ve as­sured I have clean fuel, I turn my at­ten­tion to the air­flow through the en­gine on both the in­let and ex­haust sides. Many small marine diesel en­gines have a foam air fil­ter on the in­let side, which must be rinsed out pe­ri­od­i­cally. Oth­ers have a re­place­able pa­per el­e­ment fil­ter. On the ex­haust side, be­cause many of us run our en­gines un­der-loaded and for only short pe­ri­ods of time (when get­ting in and out of slips or pick­ing up and set­ting an­chors) there will of­ten be car­bon foul­ing. It is there­fore worth break­ing the ex­haust hose loose every two or three years to check for this. It is OK to have a fine film of car­bon on the hose wall, but there should not be any sludge or crust. If there is, you must re­place the hoses and change your op­er­at­ing prac­tices to in­crease the load on the en­gine when it is run­ning. While you are at it, check all hoses for signs of soft­en­ing, hard­en­ing or crack­ing, and the hose clamps for cor­ro­sion of screws and bands. Re­place as nec­es­sary.

Af­ter that, take a close look at the ex­haust el­bow. This is typ­i­cally the point at which cool­ing wa­ter is fed into the ex­haust, which in turn means these el­bows ex­pe­ri­ence a com­bi­na­tion of high tem­per­a­tures and salt wa­ter in­jec­tion. Over time, cor­ro­sion is in­evitable. Some el­bows re­main in­tact for many years, while oth­ers may cor­rode through in as lit­tle as 3-5 years. A leak­ing el­bow will al­low po­ten­tially lethal car­bon monox­ide into the boat.

COOL­ING SYS­TEM: Your en­gine’s raw wa­ter cool­ing sys­tem in­jects the afore­men­tioned salt­wa­ter into the ex­haust, again typ­i­cally at the el­bow. Check the strainer for foul­ing. It is also a good idea to pop the cover off the raw wa­ter pump and check the im­peller for any signs of dam­age: no­tably crack­ing of the vanes at their base or flat­ten­ing of the tips of the vanes where they rub on the pump hous­ing. Flat­ten­ing in­di­cates con­sid­er­able wear—time to in­stall a new im­peller. Es­pe­cially if the boat has been laid up in a cold cli­mate, crank the en­gine just enough to ro­tate the im­peller a quar­ter to half a turn; some­times the vanes that are up against the cam inside the hous­ing will take on a per­ma­nent set, which in turn will cause them to not contact the hous­ing be­yond the cam, mak­ing them use­less in terms of pump­ing wa­ter.

At some point in the raw wa­ter cir­cuit there will al­most cer­tainly be a vented loop—a de­vice that pre­vents sea wa­ter si­phon­ing into the en­gine when it is shut down. This is a crit­i­cal piece of equip­ment that is rou­tinely ig­nored dur­ing ser­vic­ing. The valve at the top of the loop must be re­moved and washed clean of any salt crys­tals. If there is a leak-off hose from the valve into the bilges, make sure there are no kinks with low spots that can hold mois­ture. While you’re at it, the lower end of the hose should never be be­low the level of bilge wa­ter, an­other con­di­tion that will ren­der the vented loop in­ef­fec­tive.

Fi­nally, your raw-wa­ter sys­tem may have one or more sac­ri­fi­cial an­odes to in­hibit cor­ro­sion. If present, these must be in­spected and re­placed if more than half con­sumed. Their ef­fec­tive­ness is di­rectly pro­por­tional to their sur­face area so if you wait un­til they are en­tirely con­sumed be­fore re­plac­ing them, they will not have been work­ing prop­erly for quite some time.

BELTS: Check the ten­sion on any belts and look for signs of ex­ces­sive wear, hard­en­ing or crack­ing. The generic rule of thumb for V-belts is that you should not be able to de­press the cen­ter of the long­est stretch of belt run more than 1/3 to 1/2in with con­sid­er­able fin­ger pres­sure. For ser­pen­tine belts—the type with mul­ti­ple small grooves—you should not be able to twist the belt more than 90 de­grees. Note that the load on a V-belt is taken by the sides of the belt. If the belt and/or pul­leys have worn to the point where the belt is bot­tom­ing out in the pul­ley grooves, the belt needs re­plac­ing, maybe the pul­leys as well.

GENERAL: Every few years, closely in­spect the en­gine feet for ex­ces­sive cor­ro­sion of the metal parts, and/or soft­en­ing of the rub­ber in­serts. Some en­gine man­u­fac­tur­ers rec­om­mend re­place­ment every five years, but in prac­tice, so long as oil and diesel are not spilled on the rub­ber, they gen­er­ally will last much longer than this. Fi­nally,

clean not just the en­gine but the en­tire en­gine com­part­ment. A clean en­gine will make any leaks ob­vi­ous when it is run­ning, en­abling pre­ven­tive ac­tion to be im­me­di­ately taken.


Once the en­gine has been in­spected, we are ready to launch the boat. If you have a me­chan­i­cal “drip­less” shaft seal, as op­posed to a tra­di­tional stuff­ing box, once the boat is in the wa­ter you should pull back the boot un­til some wa­ter squirts out. This will en­sure there is no trapped air pocket that might cause the seal to burn up. That done, it’s time to start up the se­cond phase of your sys­tem’s com­mis­sion­ing pro­gram.

BAT­TERY CON­DI­TION: I am as­sum­ing you have kept your crank­ing bat­tery at least near a fully-charged state dur­ing the layup. If not, and it has been par­tially or fully dis­charged, it has likely suf­fered sig­nif­i­cant in­ter­nal loss of ca­pac­ity through sul­fa­tion. This loss of ca­pac­ity can of­ten be re­cov­ered, but re­quires spe­cial­ized charg­ing equip­ment.

EN­GINE OIL: Be­fore crank­ing, the en­gine oil level needs to be checked and the fresh­wa­ter side of the cool­ing sys­tem in­spected by re­mov­ing the ra­di­a­tor-type cap to en­sure it is full. Also be sure to open the raw-wa­ter sea­cock. We al­ready made sure the fuel is clean and the air flow through the en­gine un­ob­structed, so as long as we have a healthy crank­ing speed and good com­pres­sion, we should now—in the­ory, at least—be able to get the nec­es­sary heat to ig­nite the in­jected diesel and our en­gine more-or-less has to fire.

Un­for­tu­nately, the re­al­ity is that over a long layup the oil will have drained off the cylin­der walls and com­pres­sion may ini­tially be low. Es­pe­cially in colder cli­mates, we may there­fore have trou­ble achiev­ing ig­ni­tion tem­per­a­tures.

If you have glow plugs, these will pro­vide ad­di­tional heat. If not, open the throt­tle wide and crank. If the en­gine im­me­di­ately fires up, you have ex­cel­lent com­pres­sion. If not, the en­gine is likely a lit­tle old and tired. Let it sit for a minute or so. The pause will al­low the diesel al­ready in­jected into the cylin­der to drib­ble down onto the pis­ton rings to im­prove com­pres­sion as well as al­low the bat­tery to catch its breath (the ini­tial crank­ing will have also warmed the cylin­ders). Crank again. If the en­gine does not fire on the se­cond or third at­tempt, there is some­thing amiss that needs to be in­ves­ti­gated.

Is it smok­ing? As­sum­ing the en­gine fires, check the ex­haust for wa­ter flow to make sure the raw-wa­ter cool­ing sys­tem is func­tional. Look for smoke. White smoke is probably wa­ter va­por, and if so is of no con­cern. Blue smoke, on the other hand, comes from burn­ing oil and should rapidly clear up as the en­gine warms. If it does not, the en­gine will likely run fine with lit­tle or no risk of a se­ri­ous fail­ure any time soon. How­ever, fur­ther in­ves­ti­ga­tion is war­ranted. Black smoke in­di­cates a prob­lem with im­prop­erly burned diesel. If it only oc­curs on older en­gines dur­ing sud­den ac­cel­er­a­tion it is not a prob­lem. How­ever, in all other cases fur­ther in­ves­ti­ga­tion is rec­om­mended.

CHARG­ING SYS­TEM: Now that the en­gine is run­ning we should run some tests on the charg­ing sys­tem, which re­quires a qual­ity dig­i­tal mul­ti­me­ter. (If you don’t have one, put it at the top of your next birth­day wish list.) In­crease the en­gine speed to around 1,500 rpm; this will push the al­ter­na­tor to a rea­son­ably high level of out­put. The sin­gle most im­por­tant volt­age on most sail­boats is what is called the “bat­tery ab­sorp­tion volt­age.” To check it, set the me­ter in its DC volts mode and put the probes across the bat­tery posts to which the al­ter­na­tor out­put goes. Watch this volt­age. If the bat­ter­ies are dis­charged, the volt­age will climb slowly. When it stops climb­ing, we have reached the ab­sorp­tion volt­age. If this is be­low 14.2 or 14.4 volts, you are un­der­charg­ing your bat­ter­ies, which will sig­nif­i­cantly im­pact the func­tion­al­ity and health of your elec­tri­cal sys­tem.

If there are other bat­ter­ies aboard your boat that are par­al­leled-in, be sure to check their ab­sorp­tion volt­ages as well. If these are lower than the pri­mary bat­tery, you may have volt­age-rob­bing split-charg­ing diodes in the sys­tem, that or volt­age drop in the ca­bles and con­nec­tions. One way or an­other, if any ab­sorp­tion volt­age is low, you need to find a way to cor­rect it.

Fi­nally, if your bat­ter­ies are more than a few years old and ex­tended cruis­ing is part of the plan, af­ter a top-up charge I would also run a ca­pac­ity test to make sure they will re­main up to snuff in the months ahead. (A de­scrip­tion of this process will have to wait for a fu­ture ar­ti­cle.)

All be­ing well, the re-launch will have gone smoothly with no un­ex­pected hic­cups. Most times that we have re­turned to Nada af­ter an ex­tended layup, I have had us me­chan­i­cally and elec­tri­cally ready for sea in just a few hours. A day or two of putting the main­sail and head­sails back on fol­lowed by pro­vi­sion­ing, sees us set up to head off­shore for an­other cruis­ing sea­son. This year we are look­ing for­ward to ex­plor­ing the At­lantic coasts of Spain and Por­tu­gal. s

Vented loops also need to be checked

This im­peller needs to go! Don’t ne­glect your en­gine mounts

Check­ing belt ten­sion

Launch day, not later on, is the time to en­sure your en­gine is ready for the com­ing sea­son

Sam­pling fuel to en­sure it’s wa­ter-free

In­spect the shaft seal as soon as the boat is afloat Mak­ing use of a dig­i­tal mul­ti­me­ter

And check the oil, of course!

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