Manfish wrote:Q1: what is the maximum or suggested maximum weight engine that can be installed on a 1979 OUTRAGE V-20?
Boston Whaler did not specify any limit on engine weight for boats made in c.1979. The best inference to make about an upper bound for engine weight is to infer the engine weight from the maximum horsepower rating, using the weight of an engine available at that time.
The c.1979 OUTRAGE V-20 hull is rated for 180-HP maximum. For more on this model see1978–1985 Outrage V–20http://continuouswave.com/whaler/reference/V20Outrage/
If we look at that as allowing twin 90-HP engines, we then can look at the weight of 90-HP engines available in c.1979. For that information I rely on a collection of the weight of older outboard engines maintained here on continuousWave
. From that collection I would guess that the OMC 90 V4 engine at about 300-lbs might be the heaviest allowed. This gives an inferred transom weight maximum of 600-lbs. However, I think powering with twin 70-HP might have been more common, and those engines would combine to weigh about 500-lbs.
Because 1979 is prior to 1983, I would infer that the horsepower rating at that time was in reference to the engine crankshaft horsepower, not to propeller shaft horsepower. The ICOMIA 28-83 standard for outboard engine horsepower
was not in use then. In ICOMIA 28-83 the rated power measurement point is defined:
3.3.1--Power shall be declared as Propeller Shaft Power at the propeller shaft of engines sold with complete propulsion units, and at the couple to the propeller shaft of engines sold with reduction or reversing gears.
If we presume that there is perhaps a 5-percent loss of power in transmission to the propeller shaft from the engine crankshaft, then in terms of modern engines (which are all rated for propeller shaft power), the maximum power would then be 180 × 0.95 = 171-HP.
This gives new inferred limits
on engine horsepower and weight of 170-HP and 500-lbs (at the most conservative) and perhaps 175-HP and 600-lbs (at the least conservative).
If your choice is to be limited to an engine made by Brunswick under their Mercury brand, then you would probably be limited to a FOURSTROKE or ProXS model.
The FOURSTROKE 175-HP and ProXS 175-HP both weigh 470-lbs (in lightest model) and should be a fit. Your friendly Mercury dealer can explain the differences between the two models.
I don't think you need to power the OUTRAGE V-20 at 175-HP to get decent performance. The PAU HANA, another OUTRAGE V-20 which is used primarily for angling, gets quite good performance from just 115-HP, hitting about 36-MPH using a plastic propeller.