Just wondering is a stern drive can be changed to a newer one?

[wipe_out]

Seem to me there are lots of great looking older boats at really good prices that would make a brilliant project.. The vast majority in the sizes I have been looking at are on stern drives.. Now I know that the general feeling is that old stern drives or stern drives that have been poorly maintained are pretty much doomed.. So lets assume that's the scenario and the drive is dead..

So cost aside.. Purely from a mechanical perspective..

Is it relatively easy to replace an old stern drive with a new one?
In other words are the required holes in the transom roughly the same between old and new drives or does it require major rebuilding of the transom to "move" the holes?

Can the old engine be easily connected to a new stern drive or does the whole engine and stern drive have to be replaced as a complete unit?

Just wondering..

 

[jimmy_the_builder]

I'm sure volvopaul or spannerman will be along in due course with the expert answer - but my lay understanding is that there are basically three parts to this, the outdrive, the transom shield, and the engine. Whilst I imagine it would be theorectically possible to mate some contemporary leg and transom shield with a legacy engine, in practice surely you'd just buy the entire package and minor-mod the transom to accept the new shield, and the bearers for the new engine mount positions. If you were thinking about a VP bundle for example, I would have thought that the advantages of integrated EVC control of engine and leg would be quite attractive.

Cheers
Jimmy

 

[volvopaul]

I would not spend good money on a old boat you will never get your money back on the outlay.

Volvopenta did some deals this year on packages but I think that's over now, boat shows are the best time to get a deal but when you come to sell I doubt someone will buy your boat that's dated in design just because its got a newish engine and drive.

If say you bought a very cheap petrol boat you can get good used and refurbished engine and drives, I come across them from time to time. The main issue with drives and shields is corrosion, parts are horrendously high, boats from the 90s are now on the list for new drives and shields, some keep going its all dependent on how well they have been looked after from the start.

My advise is think it through seriously before you buy.

 

[wipe_out]

I would not spend good money on a old boat you will never get your money back on the outlay.

Volvopenta did some deals this year on packages but I think that's over now, boat shows are the best time to get a deal but when you come to sell I doubt someone will buy your boat that's dated in design just because its got a newish engine and drive.

If say you bought a very cheap petrol boat you can get good used and refurbished engine and drives, I come across them from time to time. The main issue with drives and shields is corrosion, parts are horrendously high, boats from the 90s are now on the list for new drives and shields, some keep going its all dependent on how well they have been looked after from the start.

My advise is think it through seriously before you buy.

Those are absolutely valid points and I think there would have to be a good reason for spending the money considering what older boats sell for and the pretty high price of drives and engines..

But..

How difficult/big is the job of changing the drive to a current model?

 

[PCUK]

The answer to your initial question is quite easy. You just need the appropriate conversion plates if the drive is different. If you really like the boat then spend the money, you will certainly get a better return when you come to sell but surely the point is to have the boat you like and want and not concentrate on the cost, otherwise why have a boat at all?.

 

[rbcoomer]

Unless you are going to gain some other significant benefit in terms of economy or performance, I'm not sure I see the point. I'd probably save some money and have the original outdrive refurbished (doing mine myself - Alpha One Gen1) or replace like with like. From what I've read here the criticisms of outdrives etc, age isn't really so much of a factor and reliability itself is down to maintenance and a bit of luck! The weak points seem to revolve around impacts, entanglement and water ingress - I don't see how a new unit vs a well maintained old unit would improve odds on any of these and the prices of old units seems to support this? If the drive is dead then an exchange could be a viable option as parts are possibly salvageable and might result in a better overall deal but if this means changing the transom plate etc and you otherwise don't have to, then costs will probably outweigh benefits? (IMHO )

I can understand the logic if changing the engine to say diesel where new gear ratios or heavier duty drive is required (e.g. Alpha to Bravo X) or if buying a new package of engine and drive because engine is significantly more powerful/economic, but not convinced that changing the drive to a newer unit is in itself a guarantee of reliability as they can all break!

 

[julians]

I think you have more likelihood of an older drive failing than a new one, but new ones can fail too. So replacing drive is no guarantee of easy maintenance. I think id just be tempted to run it and see how it goes, and if it breaks then just replace with like for like.

The alpha drive on my sea ray failed after 3 years/200 hours, i'd owned it from brand new and it had been properley serviced each year. One of the cogs in the drive sheared a couple of teeth off. I had it rebuilt (cost circa 2k), never did find out why it failed, there was nothing obvious at fault, ie no water in oil etc.

 

[spannerman]

If its a Mercruiser then all the transom assemblies are the same, just a couple of extra holes if its very old, so plug and play. All Mercruiser motors connect the same way so no problem of compatability if keeping the original engine, just make sure you get the correct gear ratio drive for the engine you have.
If its a Volvo there are differences between old and newer transoms but nothing that can't be modified.
If going from Volvo to Mercruiser or the opposite then there are ready made adapter plates available to save filling big holes where the previous transom shield was.
Whatever you decide it will mean engine out to replace the transom Shield, the drive itself is easy to replace but I'd replace everything external if you are planning to keep the boat, assuming the engine is OK, if not then perhaps a complete repower is a solution then you can decide petrol or diesel and how much horsepower and which manufacturer you prefer, but bear in mind you will also have to upgrade the controls and replace the instrruments if changing from one make to another.

 

[wipe_out]

If its a Mercruiser then all the transom assemblies are the same, just a couple of extra holes if its very old, so plug and play. All Mercruiser motors connect the same way so no problem of compatability if keeping the original engine, just make sure you get the correct gear ratio drive for the engine you have.
If its a Volvo there are differences between old and newer transoms but nothing that can't be modified.
If going from Volvo to Mercruiser or the opposite then there are ready made adapter plates available to save filling big holes where the previous transom shield was.
Whatever you decide it will mean engine out to replace the transom Shield, the drive itself is easy to replace but I'd replace everything external if you are planning to keep the boat, assuming the engine is OK, if not then perhaps a complete repower is a solution then you can decide petrol or diesel and how much horsepower and which manufacturer you prefer, but bear in mind you will also have to upgrade the controls and replace the instrruments if changing from one make to another.

Thnaks.. That's very much what I was interested to know..

 

[oldgit]

Do not forget to factor in the labour costs !
Would always be inclined to make very very sure that the stern of the boat concerned is in a fit state to handle any extra power from new unit.
On older stern drive boats any water which has pentrated the stern via the transom assembly over the years,will damage the internal wood panel and require substantial remedial work before you can even start enlarging/reducing the holes.

 

[rbcoomer]

Do not forget to factor in the labour costs !
Would always be inclined to make very very sure that the stern of the boat concerned is in a fit state to handle any extra power from new unit.
On older stern drive boats any water which has pentrated the stern via the transom assembly over the years,will damage the internal wood panel and require substantial remedial work before you can even start enlarging/reducing the holes.

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