Mercury 40 gearbox

[paulbrown22]

The gearbox on the 2011 Mercury 40 4-stroke EFI ELPT 3 cylinder (Model 1A40413KZ, Serial 1C159134, gearbox part number 8M0021572) on our sailing club safety boat has just imploded and we need to replace. Our other safety boat runs a brand new 2023 Mercury 60hp, and looking at that outside at least the gearbox casing seems to be identical, although different ratios internally. Looking online at the exploded parts diagrams they seem to be nigh on the same internally, other than the final drive ratios.

Does anyone happen to know if the 60hp gearbox is compatible with the 40hp engine by any chance (drive ratio difference aside, which I can always adjust with a prop change if needed - it spends 99% of it's life at very slow speed!). As online the 60hp gearboxes seem quite easy to come by, but I can’t find one specifically for a 40hp Mercury.

Thanks,

Paul

[beamishken]

Originally Posted by paulbrown22

The gearbox on the 2011 Mercury 40 4-stroke EFI ELPT 3 cylinder (Model 1A40413KZ, Serial 1C159134, gearbox part number 8M0021572) on our sailing club safety boat has just imploded and we need to replace. Our other safety boat runs a brand new 2023 Mercury 60hp, and looking at that outside at least the gearbox casing seems to be identical, although different ratios internally. Looking online at the exploded parts diagrams they seem to be nigh on the same internally, other than the final drive ratios.

Does anyone happen to know if the 60hp gearbox is compatible with the 40hp engine by any chance (drive ratio difference aside, which I can always adjust with a prop change if needed - it spends 99% of it's life at very slow speed!). As online the 60hp gearboxes seem quite easy to come by, but I can’t find one specifically for a 40hp Mercury.

Thanks,

Paul

Probably the easiest thing to do would be try swapping them over , a bit of a pain but not a huge issue in the grand scheme, the 40hp needs to come off anyway & a good opportunity to service & check the impeller on the 60 while your on.
Probably unlikely anyone has tried this if they are different ratios but like you say a prop change should get you where you need to be.

[paulbrown22]

Originally Posted by beamishken

Probably the easiest thing to do would be try swapping them over , a bit of a pain but not a huge issue in the grand scheme, the 40hp needs to come off anyway & a good opportunity to service & check the impeller on the 60 while your on.
Probably unlikely anyone has tried this if they are different ratios but like you say a prop change should get you where you need to be.

Thanks Ken - yes, just a bit of a pain at this club getting the only remaining working RIB out the water, and a bit of a shame to start removing the gearbox on a brand new engine that's only 2 months old and barely done 10 hours work! But potentially we have to do that if we want to find the answer...

[beamishken]

Originally Posted by paulbrown22

Thanks Ken - yes, just a bit of a pain at this club getting the only remaining working RIB out the water, and a bit of a shame to start removing the gearbox on a brand new engine that's only 2 months old and barely done 10 hours work! But potentially we have to do that if we want to find the answer...

Ahh okay sorry I missed the 'new engine" bit & assumed probably due a service this time of year 🤦*♂️must pay more attention
Hope you get sorted 👍

[gpsguru]

Originally Posted by paulbrown22

Thanks Ken - yes, just a bit of a pain at this club getting the only remaining working RIB out the water, and a bit of a shame to start removing the gearbox on a brand new engine that's only 2 months old and barely done 10 hours work! But potentially we have to do that if we want to find the answer...

Any decent Merc dealer should be able to answer that question over the phone.

The 40 and the 60 are the same 'family' of engine, so my guess it that the gearbox casing is the same.

[Davie]

Do what Ken says and pull the box, the crankshaft spline may be different.

[paulbrown22]

Thanks all - the casing seems to be an identical casting number, but Merc say they aren't interchangeable between the 40 (3 cylinder) and 60 (4 cylinder) without saying exactly what/why. I've been picking through the parts diagrams to try and see exactly what is different and interestingly the drive shaft shares the identical part number between the engines. The water pumps seem to be different though, and obviously some of the gears. I need to make/buy a suitable a puller tool to get the bearing carrier off the current gearbox, and then will see what's wrong with the current one and if I can scavenge some parts from a 60hp.

[willk]

Originally Posted by paulbrown22

Merc say they aren't interchangeable between the 40 (3 cylinder) and 60 (4 cylinder) without saying exactly what/why.

Possibly the same huge but somehow undefinable difference between the cost of a Child's portion and an Adult Half portion: One is 50% more expensive