Re-powering a boat with Merc 325 and III outdrive

[donwhiteside]

Hello All- This is a somewhat theorical question, but...<br /><br />My new-to-me 1972 Cruise-a-Home houseboat has a Mercruiser 325, seperate forward/reverse transmission, and a Merc III (not Bravo III) I/O. Things are working OK right now, but this engine and I/O were not well taken care of by previous owners. Evertime I need to do ANYTHING, or check prices and availability of parts for things I might have to do in the future, it is expensive, rare, and info is scarce. <br /><br />I'm wondering what options I have if I decide (or a catastrophe forces me) to replace the entire engine/drive. Is the cutout in the transom "changeable" or are there newer units that would fit? I'm assuming I would find a used/rebuilt unit, or a donor boat. For our purposes (mild cruising in the freshwater Sacramento Delta), we could get by with much less power. Is this crazy to think about?<br /><br />Thanks all.<br /><br />Don

 

[WillyBWright]

Re: Re-powering a boat with Merc 325 and III outdrive

Before you embark on such an expense, consider whether or not the boat is worth it. Especially check out the structure of the boat! A boat built in the 70s is about 99.999% certain to have considerable rot.

 

[donwhiteside]

Re: Re-powering a boat with Merc 325 and III outdrive

Actually, hardly any rot. Lived most of it's life in a covered berth, and the hull is built like a tank.<br /><br />Don

 

[tashasdaddy]

Re: Re-powering a boat with Merc 325 and III outdrive

dj, after viewing cruise-a-home website, i'd do my best to restore to original, although i am a restoration freek.

 

[donwhiteside]

Re: Re-powering a boat with Merc 325 and III outdrive

OK,OK, I am a restoration freak also, but not at the cost of my kid's college tuition. <br /><br />Back to the original question- is it possible, and if so, using what kind of engine and I/O, to change to a more modern drive train?<br /><br />Thanks,<br /><br />Don

 

[Don S]

Re: Re-powering a boat with Merc 325 and III outdrive

72 was the last year Merc used the 427 engine in a boat. Also the last year for the III Drive. It is almost impossible to find parts for them anymore as you have already found out.<br />Yes you can repower with something more modern. With shifting in the sterndrive. (Bravo) if you want to stay with Merc. The transom would have to be redone to fill the hole and recut for the present size hole which is smaller.<br />What size boat, type hull, is it and what speeds are you looking for?

 

[Bondo]

Re: Re-powering a boat with Merc 325 and III outdrive

If the Hull is worth the Investment,.......<br /><br /> Anything is Possible..........<br /><br />A "Donor Boat" is the Only way to do something like that,..........<br />Unless you're willing to cut the check to Mercruiser for All Brand New...........

 

[donwhiteside]

Re: Re-powering a boat with Merc 325 and III outdrive

The Cruise-a-Home is a 31' houseboat, using a "charter boat" hull. Best estimates are that it weighs about 15,000 lbs. (There is a 40' version that is more numerous, most of which have twin engines) I'm a novice, but I think it is a deep V. They were built for cruising Puget SOund and other fairly rough waters.<br /><br />We will confine ourselves to inland fresh water on the Delta, with MAYBE an occasional trip out to the SF Bay. Speed isn't a big need, though witht the current set-up, I hit 21 mph at WOT (aobut 4800RPM). Cruising at 2500 RPM give me about 12 Mph, more than enough for the short distances we go. We really like the cabin design and general "sturdiness" of the boat.<br /><br />Thanks for advice!!<br /><br />Don

 

[rodbolt]

Re: Re-powering a boat with Merc 325 and III outdrive

if speed is not a worry a volvo 5.7 and a DP drive will work<br /> if speed and longevity and ease of maint is a concern try a volvo 8.1 and a DPE type drive. the dpg is nice but were finding severe corroision issues with maint.<br /> but I would spend nothing on the current set up you have other than routine maintanence.

 

[Don S]

Re: Re-powering a boat with Merc 325 and III outdrive

I'm with rodbolt on the Volvo 5.7 MPI DP for your delta dawdling.<br />Just be aware they ain't cheap. A complete 5.7 320hp package (engine, drive, transom shield, instruments, etc.) will set you back around 18K.

 

[donwhiteside]

Re: Re-powering a boat with Merc 325 and III outdrive

OK, thanks guys. This boat will never be worth adding a new power train. I'll keep my eye out for good used units.<br /><br />For the present, I will use and not abuse my Merc 325/III. If nothing fails, it is a great unit- easy easy easy to work on (I dreamed of having a 427 to work on, when I was 16 in 1967!!) and very strong. I've found the parts I've needed so far, but am dreading anything major, if it occurs.<br /><br />The original question- "Can the transom be patched and reconfigured?" seems possible. I've even wondered about using a 200+ horsepower outboard???<br /><br />Anyway, thank again for the help and being such a good resource.<br /><br />Don