What's the most HP an Ericson 29 can handle?


Junior Member
This is not quite a racing question per-say as I'm talking under power, but if I was thinking about repowering an Ericson 29, what the most HP the design could benefit from? I don't fully understand the principle, but I believe any hull has an upper limit of the HP it can benefit from, and above that limit the HP is wasted? Hopefully that made sense, trying to articulate something I'm not clear on.



Sustaining Member
A4's, which were very common in 29's, put out a theoretical 30hp. The amount of power you want has more to do with what wind and tides you anticipate being up against. The M-12 (about 10hp) I have in the 28-2 does not perform well when I'm facing 15 to 20+ winds on the nose. I'd welcome a bunch more horsepower. It's about conditions and not hull speed.

Loren Beach

O34 - Portland, OR
Senior Moderator
Blogs Author
With a (per sailboat data website) 8500# displacement and 22 feet of static waterline, there is a definite upper limit to the amount of HP you can utilize. There is the limit (sort of...) to how much speed you can generate once you hit "hull speed", and my SWAG is that you might max out at about 6.5 for a top maintainable speed in smooth water with a clean bottom.
The displacement, OTOH, puts you up there with 'bigger' boats. After all, my Olson displaces only 2K # more. Our boat was spec'd out with a 23 hp diesel and when I repowered I went with a 25 hp diesel. This seems fully adequate, with a bit to spare. Beyond generalizations, it's hard to compare our hulls, with ours being much flatter aft, allowing more speed due to a more WL.

As for the common inboard used by a lot of boat builders in the 60's/70's, the A4 gas engine, it came in a couple of HP ratings with 30 being very common. My guess is that if that engine had been 'rated' at 20 HP instead, no one would have noticed any difference in real world usage.

Apologies for pontificating.... and really, I betcha that any modern diesel of about 20 HP would be 99.8% adequate for the E-29. Something like the Betamarine 20 is often pretty easy to "fit" into a boat, as well. It's a more compact block than earlier designs.

Keep posting, and let us know how your idea spools out.

As Red Green used to say on his wonderful TV show: " Keep your stick on the ice, and we're all pulling' for ya!"

Dave G.

1984 EY30+ Ludington, MI
Maybe if you are dragging a dinghy and are in area of challenging seas go to 25hp max ?

"If the women don't find you handsome, they should at least find you handy."


Curator of Broken Parts
Blogs Author
Loren's estimate is correct. Can't immediately lay hands on the raw data but this was what I measured with a fresh bottom in a calm backwater with the A4. Note that at the upper end, the prop wash on the rudder is so strong that it is very difficult to hold the boat on course. On the other hand, this is what it takes to approach Bonneville dam from downstream, or possibly to fight some of tides in the Salish Sea.

If things are as simple as they appear to me, this suggests that the answer is somewhere around 18-20 HP.


Junior Member
I really appreciate those reply's. I'm not in a position to re-power currently, but when I am I'll be coming back to this thread. Currently have 11 hp which is fine for a 1st timer, but if I reach the point where I'm on longer trips / more open water I think I'd want more hp as backup.


Member II
The Universal Diesel on my E28 scared me when I bought it three years ago. It is water cooled with 4000hrs so I installed a kicker. Here’s the thing, the Universal still runs like a Swiss watch. Realize 4000hours over 40years is a low 100 hrs per year. The kicker outboard is for sale.


Curator of Broken Parts
Blogs Author
Perhaps this thread should be tagged with the idea that a lot of this also depends on the propeller. (I.e. things are never as simple as they first appear.) The “Indigo Prop” mentioned above was designed to try to make the best use of HP available from the Atomic 4. A lot of boats are equipped with props that lug down this motor way before it reaches optimal RPM. Lots of discussion on this elsewhere.