Plane issue

[Riverrat65]

My 22 foot Sylvan Mirage with 150 HP Mercury is not running flat in the water at about 5 mph. It does ok when running lower speeds or faster. 5 is a good speed to cruise but the front pops out of the water no matter where I have the trim. Would adding a whale tail help? 14×14 prop is on the boat now.

 

[briangcc]

Ayuh...cause at 5mph you're not on plane, you're starting your climb out of the hole. This climb will point your bow up.

Lower than that, you're just plowing water as the motor isn't providing enough thrust to get it up. Higher than that and you're probably out of the hole and actually on plane - wag is 15-20mph more than likely.

I'd shuffle people around on the boat so that there's more weight in the bow to get it back down as I seriously doubt a whaletail is going to get you on plane at 5mph.

 

[flashback]

Trim tabs may help a little but at 5 mph it probably won't be much.

 

[garbageguy]

My 22 foot Sylvan Mirage with 150 HP Mercury is not running flat in the water at about 5 mph. It does ok when running lower speeds or faster. 5 is a good speed to cruise but the front pops out of the water no matter where I have the trim. Would adding a whale tail help? 14×14 prop is on the boat now.

At a 5 mph boat speed, relative to either the water, or to the land - I think you'll be digging hole w that size boat of, any configuration.

For comparison, our boats (including a 14 ft aluminum w 25HP outboard, 19 ft fiberglass inboard, and a 25 ft fiberglass with IO, trim tabs, and a 'whale-tail') will dig a hole 'at 5 mph'.

 

[harringtondav]

What @briangcc said. Between no wake and planing speeds you boat is simply plowing. The faster you plow the more resistance and the stern drops more. Tabs or an anticavitation plate fin may help, but moving gear/passengers forward will probably help as much.
.....mid engine inboard ski boats tend to work better at these speeds.

 

[jimmbo]

At 5 mph, there isn't even any water being Disturbed by the Boat. Even at 10mph, the bow isn't going to rise much, it at all on a 22 footer. If the engine is tilted up for Shallow water, I guess the Bow might rise a bit, when power is applied

 

[airshot]

At 5 mph, nothing other than weight distribution will change the way your boat rides..