As many here know I'm restoring a 27 sedan.
I was going to install new twin 300 hp Mercs w/ bravo drives in the hole below.
In reading a thread on the new GTMM 27/28 (Magnum hull) & other similar sized boats I see many have a single 600+ hp Merc racing motor set up instead of twins.
The 1 thing that was noticable in the pictures of these singles was the room in the engine bay. The twins to me look so tight shoulder to shoulder.
My questions are many, so I'm looking for pros & cons, positives & negatives from others that may have converted to a single or the other way. And what modifications did you have to do.
Thanks in advance.....

What was it set up for before? What are you expecting out of it? Personally I would do twin smallblocks. But that is just my op.

Having to work on my own boat I run a single BB in my 27 Carrera which also has a tight engine room, I have seen them with twin small blocks and seems like a royal pain to work on . I use mine on a lake though which is different than running out on the open ocean where having an extra engine can be a lifesaver.

I helped on a conversion to convert one of the factory single engine race Magnums [hull #286] MAGNUM FORCE 288 to twin engines. We built low dollar big blocks with Volvo drives and found 5 mph more than the single big block that had a speed III Merc drive. This was done in the early 80's & the owner was very happy with the outcome. With todays technology a single big block may be a good idea for a Magnum sport. However there is a sedan SNOOPY thats did race with a single engine. There are many single engine big block 28' Pantera's & 28' Sunsations out there that are great rides, but I would think twice about changing a sedan. The sedan has higher freeboard & in the wind docking her might be tuff, & stability in ruff sea's might be a little off. In the past I had a single 26' Sea Ray Sundancer, it was a handful.

Most of the feed back I'm getting concurs with you that handling during docking will be a handful.

As was said , I think that a lot depends on where/how you plan to use the boat. Open water safety, no contest. If you consider cost, it will not be cheap to glass in new stringers in your eng compartment which looks all set to receive twins. A 540 or 572 required to make 600-700 hp in lieu of twins will have a big price, (at least as much as twin small blocks) and then you need at least a bravo xr drive/gimble, hydraulic steering etc. Well built 350-375 hp small blocks with reg. bravos will be cheaper, easier to maintain, probably more reliable (less likely to strand you) and probably more well rounded handling.

I redid mine with twin small blocks. With the smaller size vs big blocks, I can get my arm between the motors. It's tight in there, but I like the maneuverability of the small blocks. If you were going to make your boat a racer it might be worth considering going to one built big block, but for an all around boat, the twins work great. Besides, it's much cooler having 2 of everything on the transom.

My 1971 "restromod" 27 Sport has a new pair of 383 ci`s on Bravo 1 drives with full power steering.
I like the sound of twins, the added security for Offshore use, a pair of handed props in place of all the power turning one way. Should I have to work in the engine compartment, 4 bolts on each side of each motor removes the Stainless Marine exhaust manifolds and I have all the space I need. Remote fit the oil filters and remote fit the block and manifold drains, what else do you need to get to that requires all this space I keep hearing about ?
Anyway that my view for what it`s worth
Kalaazar

Thanks Kalaazar, I'ld like to see pictures of your motors installation w/ remote oil filters & how you installed & ran the power steering. Your set up is similar to what I'm considering with the 72. I'm researching the single to understand the pros & cons. I'm most likely will stay with the twins. If you can't post pictures here just add @gmail.com after my member name to send pictures to my email address...

Personally I would go for it.

If your good at the docks it's never an issue anyways.
Furthur more it's rare not to have a dock hand on board
regardless of a single, twins, or tripples.

Years back I would say twins for a back up.
But power is so reliable now days with the technology
always moving forward they just seem to run and run.

Lastly my friend Check300 runs a single 30' Checkmate.
Granted the power is over the top, but it's a real eye opener
reliablity, performance available in a single,...and it idles at
500 rpms which makes it a kitten around the docks.

Jon