Are larger HP Outboards more susceptible to blown powerhead?

I've owned a few smaller HP two-stroke Outboards ranging from 9.9 HP to 60HP (and 2 9.9hp 4stroke's), never had any of them blow (knockin' on wood :lol.

Some of my buddies who run large bass boats have blown their powerheads, one on a brand new 250 XS Merc!

This got me thinking, why do you hear about blown powerheads so much more on larger bass boats but seldom do you hear about it on small outboards?

Is this a thing or do I just not hear about the smaller outboards blowing their powerheads?

It seems the less experienced, when faced with an off song motor, run the piss out of it hoping it will clear. Or will run home wot to see what is wrong.

Loose one cylinder on a 6 cylinder is not like loosing one out of two. Easier to run on one dry or hot slug with the other 5 okay... for awhile...its the other 5 that trash the motor.

I personally think it is due to a combination of factors:

1. Horsepower per cylinder
2. Boat as rigged
3. Use and duty cycle

Horsepower per Cylinder:
Think about it, a 9.9hp 2-cylinder motor is producing 5hp per cylinder, while on a 250hp V6 motor, each cylinder is ~42hp per cylinder. Bombardier has made their Rotax engines capable of producing up to 90 or so HP per cylinder, but that's the exception. Add that torque load per cylinder to the rest of the factors and I think that's what contributes to the dreaded Ka-BOOM!

Boat as Rigged:
It's been my experience that the far majority of boats (where admittedly my experience is on offshore boats) rigged wear the wrong pitch prop (too steep!) and have the motor mounted way too deep. The former, IMHO, is that Dealers mount the prop in the test bulletins, but most owners weigh down their boats far more than the light hulls "as tested".

For the depth, most OB owners don't know that to turn a deep-V hull effectively ... that YES you may need to trim the motor in some. If not, the prop blows out or ventilates. Dealers mount them a good inch or two deeper so "no one complains" about their new $20K motor, when it is User error :roll: .

Use and Duty Cycle:
V6 OBs tend to be used on very heavy or very fast boats ... and sometimes both at the same time. I knew a charter Capt of some reknown who blew a motor each and every year as he insisted on being the 1st boat on the fish, regardless of the sea state ... or the fate of his motor. Others just pound down the throttle in their role as a 'weekend warrior' without any regard to the motor's fate or health.

Properly pitched and set-up, and cared for with not only a good oil additive (if injected or mixed) or good oil change routine and smart use/duty cycle, i.e., warming it up properly, not running over-loaded and over-pitched for the load, and not running WOT all the time ... and an OB should last a long time. I mean, my gawd, just look at all of the 5hp to 90hp vintage 1970s and older OMC or Merc OBs that are out there that are still running!

But maybe the best answer is the "amount of "work" the OB is being asked to do. Add a tremendous amount of loading onto an improperly setup OB and that 'work' now becomes huge.

Besides not adding oil ... IMHO the surest way to blow up an OB motor is to lug it, i.e., like running a manual transmission auto in the wrong gear. I see most people with boats wearing too steep a pitch prop. When I try to help them and tell them they need to test the boat at WOT ... they reply "But I don't run it there ...". They just don't get it.

Everyone here is more or less onto it.
The higher horsepower per cylinder engines are more prone to failure. They will not put up with the abuse a low horsepower single or twin cylinder will. It takes heat to produce horsepower. Plain and simple. A piston in a high horsepower V-6 when run hard has to get rid of a ton of heat quickly. When a cylinder starts to fail the rest of the cylinders will happily carry the failing one along until a rod exits. Most owners are not savvy enough to hear and feel the failure quick enough to pull the throttle(s) back in time.
Low quality oil and or gasoline may stick rings and reduce the capability of a piston to get rid of heat. Once that piston passes a designed in tolerance it will stick. Build up of sediment, corrosion, and silt in water jackets....same thing.
On Carbureted V-6 engines for example bad gasoline left in carbs will affect the lower carbs differently than the top carb. The owner may know it is running poorly but thinks he can "clear it" by running it. Engine runs lean and the rest is history.
Same engine, either carbed or injected. Worn water pump. Upper cylinders will see less cooling water....rest is history.
Water in fuel, lower carbs will see it first.....rest is history.
These are but a few scenarios seen on a fairly routine basis in any good shop.
A savvy owner can and will get a full service life out of any engine if he takes care of it and runs it often and properly.

Pappy hit it pretty good. Also consider that an untrained ear can't tell the difference between running on all 6 (or 8) or running on 5 (or 7) cylinders. Even myself I've had them come into the shop saying low power but they sounded "normal" to me since I don't get to mess with the V6's and V8's very often. Know plenty of guys who will dig them out of the barn where they've been sitting for many years, dump old gas, put fresh in....or in some cases dump fresh gas on top of the old gas, then head to the lake and run it. Dirty carbs and all. And end up with melted pistons and holed blocks. I actually bought a 2004 Pro Craft with a 150 Yamaha on it that had just that happen to it, owner said $800 for the whole rig and I couldn't pass it up since that was what I was looking for. Sent the powerhead off to missouri and had them rebuild it, reinstalled and tuned it myself and then sold it as quick as I could. Boats are holes in the water that you pour money into and the bigger they are the more cubic dollars that they seem to "like".