Thunderbird Boat question.
 

I'm writing for a friend who owns a 1975, 21 foot, cathedral hulled, I/O (4
cyl. poss Chevie).
He runs the boat on a lake at 6400 feet asl. It will not 'come out of the
water', but it planes fine when two people are placed on the bow.
Is there an adjustment (stop) somewhere on the I/O drive, that limits how
far the propeller drive assembly can rotate forward?
in advance. . .thanks to 1 & all. . . charlie

Thunderbird Boat question.
 

On Jul 25, 6:05*pm, "pintlar" wrote:
I'm writing for a friend who owns a 1975, 21 foot, cathedral hulled, I/O (4
cyl. poss Chevie).
He runs the boat on a lake at 6400 feet asl. *It will not 'come out of the
water', but it planes fine when two people are placed on the bow.
Is there an adjustment (stop) somewhere on the I/O drive, that limits how
far the propeller drive assembly can rotate forward?
in advance. . .thanks to 1 & all. . . charlie

No, the drive will tilt "under" or "in" as far as the rams will go.
There is an adjustment on the side that prevents it from tilting out
too far. Some trim tabs, even the cheaper "automatic" ones, would
help a lot. One of those "whale tails" that bolts on the outdrive
would also help some but not as much as the tabs. The whale tales are
cheap.

http://www.saveonboating.com/whale-t...stabilizer.asp

It is probably a chevy 4 but merc made it's own 4 cyl for a little
while. A 4 is a bit on the small side for a 21 ft boat. Combine that
with the engine being tired after 34 years and the hull probably being
waterlogged for several hundred extra pounds and that's about all the
perfoirmance you can expect at altitude.

Thunderbird Boat question.
 

On Sat, 25 Jul 09, "pintlar" wrote:
I'm writing for a friend who owns a 1975, 21 foot, cathedral hulled, I/O (4
cyl. poss Chevie).
He runs the boat on a lake at 6400 feet asl. It will not 'come out of the
water', but it planes fine when two people are placed on the bow.
Is there an adjustment (stop) somewhere on the I/O drive, that limits how
far the propeller drive assembly can rotate forward?
in advance. . .thanks to 1 & all. . . charlie

What brand of outdrive does he have? Mercruiser?.... or OMC? If
it's an OMC, your choices are up or down. A Mercruiser might have
variable trim, just depends.
Did it just start acting like this recently? And has he recently moved
it up there from sea level? And has it been kept in the water or on a
trailer? Is the bottom clean? You've checked for bilge water, right?
We need a little more information please.
Rick