Cruising World - - Contents - By Ed Sher­man

Saildrives are quickly re­plac­ing con­ven­tional trans­mis­sions and pro­pel­ler shafts, but along with their ben­e­fits come some im­por­tant main­te­nance con­sid­er­a­tions.



f you are look­ing at a new or used boat, one of the things you need to con­sider is the propul­sion drive sys­tem. As one of Cruis­ing World ’s Boat of the Year judges for the past decade or so, I’ve ob­served first­hand the pro­lif­er­a­tion of saildrives both in multihulls and mono­hulls. Of the 24 new boats we in­spected dur­ing our 2017 Boat of the Year com­pe­ti­tion, only three had tra­di­tional shaft-drive sys­tems. One had

Iout­board en­gines, one had an elec­tric-mo­tor drive and the rest were all saildrives.

This is all quite un­der­stand­able from a boat­builder’s per­spec­tive. Once a new hull mold is made or mod­i­fied, it is much eas­ier for a builder to in­stall a saildrive, re­duc­ing la­bor costs con­sid­er­ably. Ad­di­tion­ally, be­cause the en­tire drive sys­tem is sup­plied by the en­gine man­u­fac­turer, war­ranty is­sues re­lated to the driv­e­train get passed on to them and claims are out of the boat­builder’s scope of li­a­bil­ity. In the case of shaft drives, en­gine war­ranties end at the cou­pling that con­nects to the pro­pel­ler shaft. The rest is on the boat­builder.

Since saildrives are only avail­able for en­gines up to 80 horse­power, we do still see tra­di­tional shaft drives on larger cruis­ers and in cases where builders of mid­size sail­boats are adamant about the re­li­a­bil­ity and sim­plic­ity of the tra­di­tional propul­sion sys­tems. All this said, our BOTY test­ing sug­gests that boats equipped with saildrives tend to run more qui­etly. Let’s ex­am­ine the pros and cons of each sys­tem along with some

in­sight on things you need to con­sider if you are look­ing at used boats.


Back in 2011, I penned a piece ti­tled “Be­ware the Un­pro­tected Saildrive” (cruis­ing­ 1707saildrive). Back then, the big­gest sin­gu­lar prob­lem re­lated to saildrives was ex­ces­sive cor­ro­sion, and that ar­ti­cle fo­cused heav­ily on ex­plain­ing ways to mit­i­gate the is­sue. Well, time marches on, and the saildrives I dis­cussed in that ar­ti­cle are now a few years older. So, on the used-boat side of this dis­cus­sion, we have plenty of boats out there with saildrives that have nearly a decade or more years in ser­vice, and the ques­tion is have they been pro­tected prop­erly with an­odes? Have the own­ers fol­lowed en­gine-man­u­fac­turer ser­vice-in­ter­val recommendations? If you are look­ing at new boats and are think­ing about long-term own­er­ship, or per­haps long-dis­tance cruis­ing to re­mote ar­eas of the globe, there is plenty to con­sider as well.

Is cor­ro­sion still an is­sue? Ab­so­lutely! It can’t be em­pha­sized enough, alu­minum saildrives are ex­tremely vul­ner­a­ble to cor­ro­sion, es­pe­cially in salt wa­ter. It has been such a prob­lem that Yan­mar is­sued a ser­vice bul­letin back in 2010 ad­dress­ing the is­sue.

An­ode se­lec­tion and siz­ing for saildrives is crit­i­cal, notes the bul­letin. Keep in mind that the an­ode in­stalled on the drive is in­tended to pro­tect the drive only. Any ad­di­tional un­der­wa­ter metal on the boat is go­ing to need ad­di­tional an­odes. An­ode ma­te­rial is crit­i­cal too. Rather than zinc, more boats are mov­ing to alu­minum-al­loy an­odes for salt- and brack­ish­wa­ter ap­pli­ca­tions. In fresh­wa­ter sit­u­a­tions, mag­ne­sium is the ma­te­rial of choice, but it should never be used in brack­ish or salt wa­ter as it won’t func­tion prop­erly and dam­age is sure to en­sue.

The an­tifoul­ing paint used both on the drive it­self and the en­tire bot­tom of the boat should not con­tain any cop­per, per Yan­mar. Cuprous ox­ide (cop­per) is the tra­di­tional ma­te­rial used in al­most all bot­tom paints, so you’ll want to be care­ful when choos­ing any an­tifoul­ing.

Above and be­yond that, even the slight­est chip in the paint on a saildrive will open the door to al­most im­me­di­ate cor­ro­sion of the drive hous­ing. The process to re­pair said chips and en­sure proper ad­he­sion and pro­tec­tion is com­pli­cated. The Yan­mar ser­vice bul­letin out­lines that as well; it can be Oil

found on­line at cruis­ing­world .com/0707yan­mar.

If your boat is plugged in at a dock most of the time, you will need a gal­vanic iso­la­tor in­stalled in your shore-power sys­tem. With­out the iso­la­tor, you run the risk of your boat’s an­ode(s) help­ing to pro­tect one of your dock­mates’ boats that may have inad­e­quate pro­tec­tion in­stalled. That sce­nario will cause your an­odes to be de­pleted much more quickly than nor­mal, ex­pos­ing your own drive units to po­ten­tial dam­age.

The im­por­tance of main­tain­ing ap­pro­pri­ate lev­els of “hull po­ten­tial” — an elec­tri­cal term that ad­dresses cor­ro­sion pro­tec­tion — as pre­scribed by drive man­u­fac­tur­ers is so crit­i­cal that I would rec­om­mend in­stalling a hull-po­ten­tial me­ter on any boat equipped with saildrives. This me­ter tells the op­er­a­tor in real time if they have suf­fi­cient an­ode pro­tec­tion in­stalled.

Re­gard­less of the make or model of your saildrive, fol­low­ing the ad­vice pro­vided in the Yan­mar bul­letin is


go­ing to help you keep cor­ro­sion at bay.


Saildrives are just like out­board en­gines in the sense that the lower unit of ei­ther is where the ac­tual gears for for­ward and re­verse are lo­cated, so lu­bri­cat­ing oil needs to be sealed in and wa­ter must be kept out. The es­sen­tial dif­fer­ence in the case of the saildrive is that it stays sub­merged 24/7; be­sides the threat of cor­ro­sion, it makes any leak­age a big prob­lem that may go un­de­tected.

From a main­te­nance per­spec­tive, drive makers all rec­om­mend at least an­nual drive oil changes and in­spec­tion of the fluid’s color for any sign of milkiness, which in­di­cates wa­ter in the oil and lower-unit seal leak­age. If con­tam­i­na­tion is found, a haulout and seal re­place­ment will be nec­es­sary.

Be­sides the unit’s gear-case seals, the drive assem­bly is sealed around its perime­ter with the hull of the boat. This seal was one of my big­gest wor­ries about the tech­nol­ogy ini­tially, be­cause a fail­ure here would cre­ate a sig­nif­i­cant point of en­try for wa­ter. It turns out my fears were un­war­ranted. The his­tory here is quite good, in fact, and I’ve not heard of any fail­ures.

That said, we are at what I be­lieve may be a turn­ing point in the his­tory of saildrives. The ma­jor drive man­u­fac­tur­ers in the United States, Yan­mar and Volvo Penta, rec­om­mend re­place­ment of the blad­der seals ev­ery five and seven years, re­spec­tively. But based on my re­search of some ma­jor full-ser­vice boat­yards, peo­ple are not hav­ing the work done at the rec­om­mended in­ter­vals. In fact, a quick scan of some of the ma­jor on­line fo­rums brought me to the J/109 group, where this topic is a ma­jor dis­cus­sion point. It seems many own­ers are go­ing 10 years and longer be­fore re­plac­ing the outer and in­ner blad­der seals on their saildrives. Cost is prob­a­bly the driv­ing rea­son for the de­lay. Pric­ing that I found var­ied from $2,500 to $4,000, de­pend­ing upon the drive’s lo­ca­tion and how it was in­stalled. Own a cata­ma­ran? Mul­ti­ply by two.

Ba­si­cally, re­place­ment of seals re­quires lift­ing the en­gine off its bed so the work can be per­formed. On some boats, ac­cess is go­ing to be quite lim­ited and en­sure a la­bor-charge night­mare, and it’s a task that al­most cer­tainly tran­scends the ca­pa­bil­i­ties of most do-it-your­selfers.

One rec­om­mended an­nual check that is not too dif­fi­cult is to test the mois­ture sen­sor in­stalled on most units to in­di­cate wa­ter in­tru­sion past the outer seal. It is rec­om­mended that an­nu­ally, an owner or me­chanic un­screw the sen­sor and dip it in a cup of wa­ter to see if the alarm warn­ing light goes on.

Close to home at least, an owner would know that if the outer seal did be­gin to leak, there would be ad­e­quate warn­ing that work is needed im­me­di­ately. I’m not sure how I’d feel about that no­ti­fi­ca­tion half­way across the Pa­cific

on the way to Tonga, but then again, I think if I were go­ing that far afield with a saildrive-equipped boat, I’d be in­clined to re­place th­ese seals be­fore­hand.

In fair­ness, I’ve been on board many mono­hull cruis­ing boats with shaft drives and drive seals that were in­ac­ces­si­ble, per­haps with a gen­er­a­tor in­stalled di­rectly over the tra­di­tional stuff­ing box or drip­less shaft unit. This is a real is­sue for any voy­ager.

Re­search on the re­sale value of older boats that of­fered both saildrive and con­ven­tional prop shaft-drive set­ups showed a def­i­nite pref­er­ence to­ward the shaft-drive con­fig­u­ra­tion. Boats from Cana­dian builder Hin­ter­hoeller used both saildrives and con­ven­tional shaft drives back in the 1980s. The boats equipped with the saildrives have shown about a $10,000 lower price when com­pared with the shaft-drive of­fer­ings.


Re­cent re­ports from the field in­di­cate there are prob­lems with shift­ing for both Volvo and Yan­mar saildrives. The so­lu­tions, like the is­sues, are con­sid­er­ably dif­fer­ent.

Volvo rec­om­mends a change in the gear oil used with its units. Orig­i­nally, the com­pany rec­om­mended the use of au­to­mo­tive au­to­mat­ic­trans­mis­sion fluid. Now it rec­om­mends the use of SAE 15W-40 en­gine oil for all drives made af­ter Septem­ber 2010. When sail­ing, one of the ques­tions that of­ten comes up is what to do with the gear shift when the en­gine is not run­ning to keep the pro­pel­ler from free-wheel­ing.

Volvo rec­om­mends set­ting the con­trol lever in re­verse if a fold­ing pro­pel­ler is equipped. If a fixed pro­pel­ler is fit­ted, ei­ther neu­tral or re­verse is ac­cept­able.

As for Yan­mar, the com­pany has plenty of doc­u­mented prob­lems with its cone-type clutches slip­ping, most par­tic­u­larly on its SD40 and SD50 mod­els. The SD20 and SD30 mod­els used dif­fer­ent clutch de­signs and do not have any his­tory of is­sues. Re­gard­ing the SD40 and SD50 mod­els, a rou­tine-main­te­nance re­quire­ment is to in­spect, re­place or “lap” (re­seat) the cone clutch mech­a­nisms of the drives ev­ery 500 hours, and Yan­mar rec­om­mends re­place­ment of the cones ev­ery 2,000 hours. Most do-it-your­self sailors prob­a­bly will not be will­ing to dive into this project, and the num­bers I found on­line for this ser­vice topped out at about $4,000! In my on­line search­ing, I did find one ser­vice bul­letin that made recommendations on what to do to up­grade from a model SD40 or SD50 saildrive to the new­est SD60 se­ries. The SD60 uses a dif­fer­ent kind of clutch mech­a­nism — mul­ti­disc ver­sus cone — that doesn’t have the slip­page prob­lem. The new­est Volvo saildrives also use mul­ti­disc clutch mech­a­nisms.

Check­ing pric­ing on the Yan­mar SD60, I came up with a ball­park re­tail price of $5,000 for a com­plete new drive. There are some ad­di­tional parts re­quired for a con­ver­sion, but it’s all quite doable. This price does not in­clude la­bor.

In a nut­shell, if I were look­ing at boats with Yan­mar saildrive propul­sion, new or used, I’d be check­ing driveg­ear model num­bers.


Com­pa­nies such as Catalina and Hall­berg-rassy still use tra­di­tional shaft drives across their model ranges, and the builders say they have no plans to change any­time soon. Larger sail­boats also rely on con­ven­tional shafts be­cause saildrives are not avail­able for en­gines above 80 to 85 horse­power.

As I think back on my own ex­pe­ri­ences ser­vic­ing boats with shaft drives, all the pro­ce­dures were rel­a­tively easy and, for the most part, fell into a pos­si­ble do-it-your­selfer’s re­al­ity. I never had to worry about a blad­der leak caus­ing a boat to sink. I never fret­ted about an alu­minum drive case dis­solv­ing out from un­der the boat due to gal­vanic cor­ro­sion. Shift­ing was mostly a trou­ble-free ex­pe­ri­ence. The only ma­jor chal­lenges were cut­lass-bear­ing re­place­ment, be­cause it re­quired a spe­cial puller to get the job done, and the oc­ca­sional shaft seal that was in­ac­ces­si­ble due to a builder in­stalling too much gear on top of the shaft and stuff­ing box.

I’m sa­vor­ing those fond mem­o­ries be­cause if I were look­ing for a new cruis­ing sail­boat in the 30- to 50-foot range, mono or multihull, it would prob­a­bly have one or more saildrives in­stalled. We’re look­ing at a par­a­digm shift here: No main­te­nance slack­ers al­lowed!

Ed Sher­man is ed­u­ca­tion vice pres­i­dent for the Amer­i­can Boat & Yacht Coun­cil and a fre­quent CW con­trib­u­tor and Boat of the Year judge.

A zinc an­ode sits be­tween the bronze fold­ing pro­pel­ler and the gray body of the saildrive (above). Be­cause the zinc is split, it’s eas­ily re­placed with­out re­mov­ing the prop.

Oil check point Ac­cess is key to proper main­te­nance of any saildrive. Trans­mis­sion fluid and oil should be checked rou­tinely, and be on the lookout for any milky-look­ing fluid that would in­di­cate wa­ter in­tru­sion. In the in­stal­la­tion on the left, ser­vice points are easy to get to; on the right, the en­gine space is cramped, mak­ing main­te­nance more dif­fi­cult.

On the left, a drip­less shaft seal is eas­ily reached should emer­gency ser­vice be re­quired. On the right, if the in­ner or outer seal around the saildrive needed to be re­placed, a me­chanic could take ad­van­tage of the clean in­stal­la­tion to raise the en­gine and drive and make re­pairs.

In­ner seal Trans­mis­sion-fluid cap

The tra­di­tional shaft-drive in­stal­la­tion (above left) is a me­chanic’s dream when it comes to be­ing able to ac­cess the prop shaft cou­pler, left of frame, or the stuff­ing box ad­just­ment bolts on the bronze fit­ting, pic­tured in the right of the frame. On the saildrive (above right), the cool­ing wa­ter in­take valve is easy to get at in case it needs to be closed in a hurry.

Prob­lem area Any nicks in the paint on an alu­minum saildrive hous­ing cre­ate an unfavorable an­ode-to-cath­ode re­la­tion­ship, which will al­low ex­treme cor­ro­sion to com­mence. The drive should be in­spected an­nu­ally, and painted, if nec­es­sary.

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