The smallest boats with a standing-height engine room?

I had a Gobbi 27 Sport (30 feet over all 10 feet wide) from 94 till 2008, and the boat had standing engine room with sun pad closed. Full walk around the engines, only you had to sit low to port side.
Interesting for its size, the boat had rather large Volvo41s 200hp with stern drives. I think that boat had one of the best technical layouts I ever saw.
Separate boiler box (to stbd), separate battery box (to port), both molded in fiberglass. Separate fuel tank in between the cabin and ER, which you could easily remove (remove hatch floor with six screws and you take it out).
Infact once I did remove it and clean it.
Also very seaworthy, for example I did Messina to Porto Rosa (over 30 nm) in 1.5 to 2 meter waves to the nose at 20 knots with no slamming.

The very reason I keep coming back to the Hatts...... I'm planning to do my own maintenance to a very large extent and accessibility is paramount. Ask me about my rear engine, rear radiator motor home.....

In terms of engine room space, check out the Grand Banks 52 Europa. I'm 6'4" and can stand up in the engine room next to the engines and generator. Lots of space. Getting to the engine room is not quite walk-in though. There is a ladder from the saloon or you can get to it from the lazarette but that requires bending over quite a bit. Engine room access was one of the primary reasons for us to go with the GB52 Europa.

Well, that is the rub. On these size boats, you still have to bend over to work on everything because most things are not mounted on the wall at waist level.

Have a look at a Sunseeker 52' Manhattan(Newer model years). Surprising amount of space in the Engine Room. I'm 5'10" and have all kinds of room above my head and can essentially walk around both engines with ease, as well as get to the Seakeeper and GenSet. There is a small walkway through a bulkhead to get to the running gear, but rarely have to go in there.

Both the 48' and 53' Ocean Yachts MY have stand up/walk in engine rooms. 1988/1991 or so..

48 ,56,53 Ocean Motor Yachts. Great layout and....they are affordable.

Grand Banks 49 classic

+1, I really like the layout on those boats.

I think the OP's question also revolves around whether the engine is covered by hatch covers or is a walk in ER. My 33 Egg had engine hatches in the salon and I could get anywhere on those engines. Presently I have a walk in ER with about 5 feet of head room. I find it very comfortable. I have a thick knee cushion and a tool chest seat down there and they allow me to work in corfort -seated or kneeling. What's equally important to me is being able to get to the outboard side of the engines. My generator is located squarely at the head of and between both engines. It eliminates easy acess for an ole' cuss like me. 10 years ago it was fine, I could squeeze thru the space between engine and genny. Recently, I've thought about designing some sort of a genny mount which would allow me to laterally travese the genny one foot either way but could be locked down in place when access is not needed.

Definitely Kadey-Krogen 39 - possibly the best "couples boat" ever built.

The KK44 is on our short list. Just wish the ER was taller

That is a great boat. Hadn't seen one, now on our short list

Krogen Express 52

OP seems long gone, but this is a great thread to keep alive for those looking for stand up ER.
Mine is half stand up. Storage, fuel tanks and genset are forward and stand up. Twin cummins with heaps of room to every side with zeus pods are crouching stand up room.
2009 Californian Veneti 50. One off by Navigator before they went belly up after the 2009 US economic shenanigans.

My point is having a 50' boat with crouching stand up full access to all gear is more than fine for me, so those thinking they need full stand up ER, but don't want or need a 60+' boat, you may be surprised how less than stand up is okay.

I am 6’-2” and can get around both sides of my Prestige 590 with Zeus/Cummins pods. The engine room space was a BIG attraction for me to select this model. 2.5 gph at 8.5 knots or 49 gph at 20 knots. Not a trawler, but at slow speeds similar fuel burn.

I asked my mechanic and he indicated no issues standing up in my 48 Cabo