re-powering from volvo md17d to d2-40

[bmartinsen]

Hi All
First day at this site, very nice. I have a 20,000lb monohull and have been cruising for about 5 years it has an old Md17d, still runs but leaks oil,blows blue, over heats, water pump starting to seep, governor not well,etc. This is connected to saildrive that needs work. Anyway, I've decided on replacing it with new D2-40. The cost difference is about
5k to rebuild everything(assuming they get it right the first time) to about 15k for new.

The Prop selection is the biggest problem for me. The old engine had a 17x14 2 blade fixed. It ran well at 5kt@2k and would max at about 3k.
I know that it should be 3600 but sounded like the engine was going to
explode at 3K.( I'm going to check accuracy of tack today.)


Has anyone out there done this switch? I'm told old exhaust will work fine.
Bed will be changed but that is included with motor.

Any comments appricieted.

I currently live in Grand Cayman without any local dealers of any brand and since I have a saildrive every redo requires lifting boat. $$$ and the last time they lifted with strap under engine. /so the rebuild option can add up very fast.

Thanks
Brad

[Boracay]

Repowering reminds me of the old joke about the man who was banging his head against a brick wall.
When asked why he replied "It feels so good when I stop."

Seriously though, When I repowered Boracay with a John Deere 4045D I did spend a considerable amount of time checking measurements.

Overall size, engine and gear controls, spacing and location of engine mounts, and the size of the flexible coupling all deserve special attention.

Particularly check the location and size of the exhaust hose. Specifications are not particularly forthcoming about this and it can be a real surprise.

Check also that Volvo have not changed from rear engine mounts to gearbox mounts, and if they have what adapters are needed.

I ordered an extension for the wiring harness and this was well worth the money.

I needed to have adapters made up for the engine mounts, the gearbox /flexible coupling/propeller shaft coupling and the exhaust.

I went with new engine/gearbox mounts and feel this was worth the money.

For the propeller you can calculate from your current boat speed (GPS) and propeller shaft revolutions what your current size should be.
Then calculate what size propeller will be needed. I ended up with a prop that is way too coarse and will need to repitch by up to 4 inches when I next slip.

[bmartinsen]

Thanks for the reply. Since I'm replacing motor and saildrive the installation is a bit
simpler. Cut out old bed and put in new one over big hole in bottom.
As for the trannys both ratios or very close 2.2:1 and 2.19:1 The new engine actually has a lower max rpm at 3200 instead of old 3600. Max torque at 1800-2000. My only option from volvo appears to be 11 or 12 pitch in the 3blade folding props. Only they can't ship me both to try out
Brad
BTW -check tack accuracy-ok