changing gearborx oil

[gaiola]

Hi everyone I have a marine gearbox with reverse and I would like to change the oil of the gearbox, can someone tell me the specification of the oil ? For e.g. tell me 15/40 ,20/50 or 80/90 I am confused  thanks

[bigboy]

What make is the gearbox ? is it mechanical or semi/fully hydraulic

just to put you in the picture i have a hurth gearbox which is semi hydraulic and it tells you to use the red hydraulic rower steering fluid. I also have a technodrive full hydraulic which uses same oil. 

[Granitu]

Typically gear box oil needs to be inspected periodically and only changed if there were any issues with the gearbox.

if you changed the oil already inspect the oil colour as it would give you an idea of any issues with the gearbox.

Normally gearboxes specify whether to use ATF oil (automatic transmission fluid - the red oil) or normal engine oil, typically in the 15/40 to 20/40 range. For Malta use, oil in the 15/40 range would be fine as we do not have freezing point temperatures.

Techno drive advise that for their gearboxes one uses normal engine oil typically a 15/40.

Correct me if I am wrong on something one may always learn new stuff.

[bigboy]

Granitu my technodrive specifies ATF

[Granitu]

Granitu my technodrive specifies ATF

Pretty sure the one I have on my toyota states 15/40 oil.

Could be it varies between engines.

By any chance does your gearbox have an oil cooler?

[Granitu]

You are right big,

I had a technodrive on my previous boat.

They are PRM's

[bigboy]

No i dont have an oil cooler. it is installed on my aux engine (Technodrive TMC 60)

[Granitu]

that it then.

I got to know from a well experienced mechanic the reason why some gearboxes take atf oil vs engine oil.

It seems it all stemms down to how the cooling system was engineered. In his understanding, gearbox engines w/out oil coolers use atf oil as it can cool down without a cooler. Normally these gearboxes are more forgiving to over heating and suitable to engines who do not go above 4000 rpm. Technodrive use such design and the advantage is that they are less expensive and easier to maintain. Cost of any rebuild would be pretty low.

On the other hand, gearboxes with coolers are designed to have a more efficient cooling system cause they are designed for engines that operate at higher RPM's and hefty loads. Funnily, ATF oil is too thin to be employed on these gearboxes and with the cooling system available, ATF oil would operate at a very unreasonable cold temperature.
The most suitable oil is a low synthetic 15w40. Also, a 20w40 is suitable too considering we do not have freezing temperatures. PRM are a brand that use such design and although being one of the best options, they tend to be notoriously costly to rebuild and repair. Apart from that, replacing gearbox oil is quite a tedious process since the oil measuring stick on PRM's is frustratingly difficult to work off.

Both systems are good and for the sake of simplicity, it is better to have a technodrive for engines who work within the 3000 rpm range as they are easier to maintain.

One important note. I was advised that whenever changing gearbox oil, always operate the gearbox for at least 15 mins before changing oil due to oil expansion. Also, operating a gearbox at low revvs wears the clutch faster - I was suggested that every 2 hours the boat is revved up to 1000 -1500 rpm.

[joe]

proset
Granitu

[gaiola]

Hi guys I consider to take the gearbox off so I can see if there's any oil leak and after a very clean up with power wash a table on the side can be visible now and it says  that you have to change the oil every 300 hours and the grade have to be straight 30 or straight 40 , many thanks for those how was interested on mine post

[Granitu]

Hi guys I consider to take the gearbox off so I can see if there's any oil leak and after a very clean up with power wash a table on the side can be visible now and it says  that you have to change the oil every 300 hours and the grade have to be straight 30 or straight 40 , many thanks for those how was interested on mine post

The thing is that you will not find straight 30 oil i think nowadays - At least I did not when I tried.

What they recommend now is a multigrade of 10w 30 or 15w 40 for malta climate.

[bigboy]

Guys from personal experience always check gearbox oil level as i ruined my hurth gearbox 2 years ago. A seal got busted and oil drained out of the gearbox. My bad as i do not check bilges.. pump always on so water is pumped out. It costed me over 1k to fix :/

[bigboy]

To top it all up, i got it fixed and back in place, back out to the fishing grounds.... gearbox nearly empty once again.... mechanic told me all seals were changed but another seal got busted !

[Granitu]

To top it all up, i got it fixed and back in place, back out to the fishing grounds.... gearbox nearly empty once again.... mechanic told me all seals were changed but another seal got busted !

That is something I always do and the reason why I removed the automatic bilge switch. I know It is risky as I am not covered from a risk of the boat drowning from a failed water inlet but I prefer knowing what water is in my bilge rather than having something which unfortunately may hide a problem from you.

In any case everytime i close all water inlet valves.... always hoping that when I switch on then I do not forget them closed.... haha

[gaiola]

Just to tell Granitu that oil straight 30 and straight 40 you can find easily at Lourdes patrol station,the first patrol pump I stopped I find so I don't think is it a problem from your locality to buy, the only problem if you can say it a problem is that you don't find it in a liter so you have to buy a gallon