Slow Cruising Speed Question
 

I recently did a sea trial on a boat I'm thinking about buying, a 1990
Thompson 288 Adventurer flybridge cruiser with twin 350 mercruiser inboards.
I was disappointed to find that at 3200 RPM, trimmed for max speed, it could
only make 13-14 knots, as indicated by GPS, and at WOT, around 4800 rpm, it
topped out at about 24. This was in glass-smooth protected waters with
little wind. The engines seemed to be running fine, but this seems a rather
slow boat. It's my understanding that much over 3200 rpm the 4bbl carbs
open up and send fuel consumption through the roof. Any thoughts or advice
for this beginner?

Steve

Slow Cruising Speed Question
 

Something's not right. Was the bottom clean? The next thing I'd check is
the size of the props against the original equipment and find out what RPMs
they spec'd at WOT. It's hard to believe a hull could be that inefficient
but it's certainly possible.

You're right about the rpms and secondaries. Normally they open about 3400
rpm and when they do, most fuel consumption curves start to hockey stick.

jps


"Steve Helling" wrote in message
...
I recently did a sea trial on a boat I'm thinking about buying, a 1990
Thompson 288 Adventurer flybridge cruiser with twin 350 mercruiser
inboards.
I was disappointed to find that at 3200 RPM, trimmed for max speed, it
could
only make 13-14 knots, as indicated by GPS, and at WOT, around 4800 rpm,
it
topped out at about 24. This was in glass-smooth protected waters with
little wind. The engines seemed to be running fine, but this seems a
rather
slow boat. It's my understanding that much over 3200 rpm the 4bbl carbs
open up and send fuel consumption through the roof. Any thoughts or
advice
for this beginner?

Steve

Slow Cruising Speed Question
 

Maybe the anchor was down dragging on the bottom =)

"Steve Helling" wrote in message
...
I recently did a sea trial on a boat I'm thinking about buying, a 1990
Thompson 288 Adventurer flybridge cruiser with twin 350 mercruiser
inboards.
I was disappointed to find that at 3200 RPM, trimmed for max speed, it
could
only make 13-14 knots, as indicated by GPS, and at WOT, around 4800 rpm,
it
topped out at about 24. This was in glass-smooth protected waters with
little wind. The engines seemed to be running fine, but this seems a
rather
slow boat. It's my understanding that much over 3200 rpm the 4bbl carbs
open up and send fuel consumption through the roof. Any thoughts or
advice
for this beginner?

Steve

Slow Cruising Speed Question
 

One other thing to mention is that the tachs don't agree. When the port
engine tach indicated 3200, the SB tach indicated 4000, with the engines
synched. It may be that both are reading high and we weren't actually
running at cruising rpm, but given the throttle positioning and engine
sound, it did seem like the engines were around the 3000 rpm range, so I
chose to believe the lower tach, as did the boat owner.

The bottom is very clean. The boat is kept in dry storage. The trim tabs
work properly. The props are in very good condition, which makes me think
they may have been replaced at some point, and may not be optimal.

And no, Rob, the anchor wasn't down, although it almost felt that way ;) I
can promise you I won't be buying this boat until/unless I get to the bottom
of this.

Steve

"Steve Helling" wrote in message
...
I recently did a sea trial on a boat I'm thinking about buying, a 1990
Thompson 288 Adventurer flybridge cruiser with twin 350 mercruiser
inboards.
I was disappointed to find that at 3200 RPM, trimmed for max speed, it
could
only make 13-14 knots, as indicated by GPS, and at WOT, around 4800 rpm,
it
topped out at about 24. This was in glass-smooth protected waters with
little wind. The engines seemed to be running fine, but this seems a
rather
slow boat. It's my understanding that much over 3200 rpm the 4bbl carbs
open up and send fuel consumption through the roof. Any thoughts or
advice
for this beginner?

Steve

Slow Cruising Speed Question
 

Subject: Slow Cruising Speed Question
From: "Steve Helling"

Any thoughts or advice
for this beginner?


How much does it weigh?

Capt. Bill

Slow Cruising Speed Question
 

Supposedly, 9200 pounds, but I haven't been able to confirm that yet.


"LaBomba182" wrote in message
...
Subject: Slow Cruising Speed Question
From: "Steve Helling"

Any thoughts or advice
for this beginner?


How much does it weigh?

Capt. Bill

Slow Cruising Speed Question
 

Damn, the thing should fly!

I've got 26000# and another 12' with twin 454s and get similar speed to what
you quoted.

"Steve Helling" wrote in message
...
Supposedly, 9200 pounds, but I haven't been able to confirm that yet.


"LaBomba182" wrote in message
...
Subject: Slow Cruising Speed Question
From: "Steve Helling"

Any thoughts or advice
for this beginner?


How much does it weigh?

Capt. Bill

Slow Cruising Speed Question
 

The broker's website listing for this boat (Blanton & Steward, Panama City,
FL, www.blantonandsteward.com) shows 22 cruise and 26 top. He agrees with
me that there is a problem. The owner's agent didn't seem to think there
was a problem, though. Imagine that!

Steve H.

"WaIIy" wrote in message
...
On Fri, 19 Sep 2003 13:14:16 -0500, "Steve Helling"
wrote:

Supposedly, 9200 pounds, but I haven't been able to confirm that yet.


Yachtworld has a few of them...

5.0 mercs Cruise 22 Top 30

5.7 mercs Cruise 22 Top 26

Doesn't make sense

Slow Cruising Speed Question
 

"Steve Helling" wrote in message
...
Any thoughts or advice
for this beginner?


Thought one: How accurate do you believe the speed measurements to be? If
you are basing it on the spedometer from the boat, it could be way off.

Thought two: How did the boat feel at around 3200 RPMs? At 13 knots I
would expect it to be plowing big time, hard to handle, bow up high, etc.
Not a place you want to operate. Once she gets on plane the bow should drop
and the speed pick up.

Thought three: I have a 36' Carver, weighs in at about 19,000 pounds, with
twin 350 Crusaders. I top out at about 22 knots, and can cruise at 3800 RPM
at around 18 knots. If I am not able/wanting to go that fast I drop back to
around 1200 RPM and move along at 8 to 10 knots.

Thought four: If this is a sea trial, then I am assuming that the boat was
pretty ba I.E., the cupboads weren't full of stuff, the water tank
probably wasn't full, there wasn't a 105 quart ice chest full of beer and
sodas on the back deck, etc. Once you buy the boat and load it up with all
your stuff, you can bet you will lose some of the speed. If you don't like
it now, you sure won't like it once you load it down.

If you want a fast boat, this doesn't sound like it. It certainly seems
like a 28 foot boat should be able to plane easier and move along at a
faster rate.

Rod McInnis

Slow Cruising Speed Question
 

Rod,

Thought one: How accurate do you believe the speed measurements to be? If
you are basing it on the spedometer from the boat, it could be way off.

The measurements were taken with GPS, therefore accurate, except for
currents, which were averaged out given that we went several different
directions and the speeds I reported were an average. What is in question,
though, is the accuracy of the tachs, as one read 3200 while the other read
4000, and both may have been reading high. I don't remember what they read
at WOT, but believe the higher of the two read well over 5000. The owners
are currently addressing the tach situation.


Thought two: How did the boat feel at around 3200 RPMs? At 13 knots I
would expect it to be plowing big time, hard to handle, bow up high, etc.
Not a place you want to operate. Once she gets on plane the bow should
drop
and the speed pick up.

The boat, at 12 knots (3200 on the lower tach), was not on full plane, but
by 15 - 18 knots, was on plane. The bow of this boat doesn't really come up
dramatically when trying to get on plane.


Thought three: I have a 36' Carver, weighs in at about 19,000 pounds,
with
twin 350 Crusaders. I top out at about 22 knots, and can cruise at 3800
RPM
at around 18 knots. If I am not able/wanting to go that fast I drop back
to
around 1200 RPM and move along at 8 to 10 knots.

Thought four: If this is a sea trial, then I am assuming that the boat
was
pretty ba I.E., the cupboads weren't full of stuff, the water tank
probably wasn't full, there wasn't a 105 quart ice chest full of beer and
sodas on the back deck, etc. Once you buy the boat and load it up with
all
your stuff, you can bet you will lose some of the speed. If you don't
like
it now, you sure won't like it once you load it down.

This was a sea trial by myself, not a surveyor. The survey with sea trial
is coming soon. Anyway, the craft had half tanks of gas, about a half tank
of water, and the cupboards did contain quite a few odds & ends. No 105
quart cooler, though :). My gut feeling, so far, is not so much that the
boat lacks power, but that the tachs are giving a false high indications, or
possibly it is not propped correctly. Hopefully, the surveyor will be able
to solve this mystery. I am also going to have the engines surveyed,
compression checked, etc.


If you want a fast boat, this doesn't sound like it. It certainly seems
like a 28 foot boat should be able to plane easier and move along at a
faster rate.

Rod McInnis