Volvo Penta DP-E Drive Oil - Frequency of Change

[boy boater]

The recommended oil change period for my DP-E Drive is every 200 hrs or at least once a year.

Putting to one side that the drive operates under water in a more hostile environment than a car gearbox (in fact my boat is on a dry racking berth which means it is in the water only when being used), the fact that it is in essence a gearbox why is it necessary to change the oil more frequently than in the case of a car's gearbox/differential, i.e often once in every several years and sometimes never in the life of the car?

It is understandable that it is necessary to change the engine oil and filter every year since this gets contaminated with the products of combustion and hence goes black in the process.

However, without these contaminants to hasten drive wear and corrosion, subject to the regular checking of propellor shaft oil seals for leakage, the checking of gaiters/boots on a regular basis (and changing, if necessary) and the periodic checking of the oil for emulsification (due to the ingress of water), surely advanced synthetic drive oil should perform perfectly well for several years?

 

[[2068]]

Outdrive gears do get quite warm - google "drive showers" to see some quite bizarre third party solutions to keeping the upper gear set cool.

Also, however good your propshaft seals are, a little bit of water does get in somehow.

You do the sums:
- Change the oil on an outdrive = £150 or so
- Don't change the oil. There is undiscovered water & milkshake in there. The case hardening is removed on the lower gear set by the water/milkshake. The gear teeth end up loosing their hardest parts as metal shavings in the bottom of the outdrive. The dealer tells you this is not economical to repair, but offers you a reconditioned outdrive for £3500.

Your choice.

 

[boy boater]

(i) Gearbox oils in cars also get hot but the oil is designed for the application/operating temperature experienced and this is presumably true for outdrive oils?

(ii) Is it really true that oil enters the outdrive regardless of how good the propshaft seals are?

(iii) I understand the impact of emulsified oils in gear boxes (incidentally, I seem to recall that Seagull outboard engines ran with emulsified oil in the gearbox by design?) but I had eliminated that possibility in my original post.

(iv) I understand the £150 vs £3500 argument, my question was all about whether there is the need to invest £150 every 12 months or 200 hours when there is no evidence that the need is there. In other words, if the condition of the outdrive and its operating conditions are good why doesn't the oil last longer than 12 months, i.e. why does it degrade in 12 months whilst some car gearbox oils are spec'ed to last for the life of the vehicle?

 

[[2068]]

You're trying to apply automotive logic to a boat.

Cars are designed to cost as little to maintain as possible when used in fleets. So, the gearbox is "filled for life". Not because it's some sort of magic oil that lasts indefinitely, nor because the gearbox in a car is a happy combustion-product-free place to be for oil to be, but because it enables the manufacturer to delete off the service item "change the gearbox oil" from the schedule. Given the duty cycle (light and frequent), this is an acceptable situation for the average motorist.

An outdrive gearbox doesn't have the same duty cycle.
An automotive gearbox is not usually left standing for weeks on end without turning.
When you do start your car, you don't fill it with rugby players, put it in second gear, then drive up a steep hill at 3/4 throttle for three hours continuously.
Your car doesn't live underwater.
Apologies to KAD44 owners, but most car engines are not so powerful that the gearbox is right on the edge of what it can handle without exploding.

So, who has designed the perfect oil for the second situation.
Answer: Nobody! The hint to this is the multitude of oils that VP have specified over the years, and the fact that an older version of the service schedule recommended that you chuck away the outdrive and put on a reconditioned one at something like 1200 hours

Given the above, a cheap way of way of making the outdrive last as long as possible is to change the oil regularly. If you want to save money, stop upgrading your phone so often

 

[boy boater]

Thank you for that, FlowerPower.
I think your second, more comprehensive reply is well argued and makes very good sense.
I will carry on changing the outdrive oil as recommended!

 

[Jim@sea]

You also have to remember that one day you may want to sell your boat and a full and detailed service history may help to sell your boat compared to a boat where the boat owner has skimped on servicing. Plus you have piece of mind.

 

[volvopaul]

Hi Boy, you cannot possibly compare the automotive logic against the marine environment, just take it that you change the oil every year and save yourself a lot of money in the future.

Even though you are drystacked and I service both boats that are permanently in the water and dry stack is abosolutely no safeguard against damage to seals etc.

You only have to get a wrap of fishing line around the prop and in seconds the seals have been damaged, keep checking the oil level as its easy for you on DS, but remember the water will be at the bottom of the gearbox, so the dipstick length may not show up water in the oil, thats why you change it every year.

2.5 litres per drive is not a lot to pay.