The actual horsepower of the E-TEC 90 was typically less than 90-HP, and it varied with the model year, as reported in the EPA test data. Depending on the year,
the "90" was rated as low as 82-HP and as high as 89-HP. The E-TEC 90 was often used to re-power MONTAUK 17 boats with very good results.
As for the E-TEC 90 H.O., I am sure it will produce more horsepower than the standard 90-HP model, probably 99-HP or close to that. Most comments I found about the V4 90 H.O. mention more low-RPM power, which seems quite likely with the extra cylinder. More low-RPM power would be useful if you expect to be towing water skiers, although these days kids do not seem to water ski; they are all getting towed around on plastic inflated toys.
A good way to see the actual rated EPA testing horsepower is to view the Emission Decal on either engine. The power will be stated in kiloWatts. To convert to HP multiply kW by 1.34.
Here are some other considerations:
PARAMETER 90 90 H.O.
Weight 320-lbs 390-lbs
Oil Tank Internal External
Alternator 25-Amperes 50-Amperes
Note that the weight difference is greater than what you seem to have assumed. Back when the MONTAUK 17 was designed, a typical 90-HP engine 20-inch-shaft model would have weighted about 300-lbs. Putting 390-lbs of the V4 90 H.O. is really pushing the transom weight into new territory. (Weight of older engines taken from an
archived article.)
The 90 H.O. is a good choice if the boat's rated horsepower limits you to an engine with a decal that says "90". But the typical MONTAUK 17 was rated for 100-HP, so the power added by the "H.O." tuning is probably within the horsepower rating.
The need for an external oil tank could be a consideration. Having the oil tank under the cowling in the standard 90 is a nice advantage in my view.
The V4 90 H.O has more alternator power available, if that is a consideration for your use.
From my general impression, the three-cylinder E-TEC 90 was perhaps the most trouble-free model of all the E-TEC engines.
Another consideration regarding the H.O. model: if the engine uses a mechanical valve in the exhaust path to affect power output at different throttle settings, those valves can be a maintenance concern. I do not know with certainty if the 90 H.O. had such an exhaust valve, but I recommend you investigate that further.
The model year of the engine is also a consideration. Minor changes made during the production epoch 2008 to 2012 are described in an article I wrote. See
E-TEC Model Year Changeshttps://continuouswave.com/forum/viewto ... 132#p35944I would look for an engine made in model year 2009, 2010, or newer, if possible.