2008 240 OUTRAGE Re-power with VERADO V8 300-HP

Optimizing the performance of Boston Whaler boats
reel connection
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2008 240 OUTRAGE Re-power with VERADO V8 300-HP

Postby reel connection » Tue Feb 13, 2024 8:55 am

Recently I re-powered my 2008 240 OUTRAGE with a Mercury VERADO 30-HP V8 engine, but I am not sure the engine mounting is at the best height. My concern is the engine mounting may be too high, particularly when compared to the original V6 engine mounting height.


Tell me your experience with engine mounting height.

Figure 1. Close-up of engine Anti-Ventilation plate with an extension to show the relationship of the AV plate to the transom and keel.
AV-plateTransom.jpg (44.74 KiB) Viewed 793 times

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Re: 2008 240 OUTRAGE Re-power with VERADO V8 300-HP

Postby jimh » Tue Feb 13, 2024 9:18 am

I do not have any experience with mounting a Mercury VERADO V8 300-HP engine on any boat, and thus not able to offer you any first-hand advice regarding what mounting height should be used on your 2008 240 OUTRAGE boat. But I do not think there is anything about the combination of your boat and engine that would change the general considerations of engine mounting height, so I will offer the following advice.

Typically for optimum performance when the boat is on plane at typical planing speed and the engine is trimmed for that speed and operation, the position of the engine Anti-Ventilation (A-V) plate relative to the flow of water around the engine gear case should be such that the A-V plate is just at or just above the waterline.

The best way for readers to pass judgement on the mounting height of a particular engine on a particular boat is for the boat operator to provide a photograph that shows the relationship of the A-V plate to the water flow when the boat is on plane and at the typical planing speeds, or perhaps in the upper range of planing speeds.

To see examples of photographs that illustrates the position of the engine A-V plate relative to the flow of water around the gear case, see this article:

A-V Plate Pictures

Perhaps the best of those photographs to show the A-V plate position is the view seen in Figure 2 below:

Fig. 2. Overhead view of engine A-V plates relative to the flow of water around the gear case at planing speeds.

Further, in order to intelligently and unambiguously describe the engine mounting height, the method to be used is to cite the position of the engine relative to the lowest possible mounting position, and to measure that increase in height above lowest possible position in units of "holes" above the lowest, with the term "holes" referring to the actual mounting holes in the engine mounting plate that are spaced at intervals of 0.75-inches apart. For more advice on how to use the "holes-up" method of description, read this lengthy article which is dedicated to that purpose and is pinned at the top of the PERFORMANCE forum:

Engine Mounting Height Nomenclature
https://continuouswave.com/forum/viewto ... ?f=7&t=739

Exactly what increase in engine mounting height above lowest possible among the options (one-hole-up, two-holes-up, three-holes-up, or on some engines four-holes-up) will produce the best performance depends on several factors. The ability of the propeller being used to operate in aerated water is a major factor. The ability of the engine cooling water to maintain the required pressure is also a very important consideration. The goal to be achieved in engine mounting height is similarly important. The absolute best full-throttle boat speed in very calm water, or the best performance in rough sea states will tend to favor different engine mounting heights.

For more discussion of engine mounting height, read this article on precisely that topic, which is pinned at the top of the PERFORMANCE forum:

Considerations in Engine Mounting Height
https://continuouswave.com/forum/viewto ... f=7&t=6618

But assessing engine mounting height from an illustration such as seen in Figure 1 is really not possible.