5000 - 8000 RPM Surprise
 

JR North wrote:
Your prop hub is slipping. Get the prop rebuilt.
JR
BTDT got the T-shirt, too

Mike Slater wrote:

I was cruising along in my 24ft pontoon boat when I got a real
surprise. Somebody please tell me how and why I could be running wide
open throttle at my normal 5500 rpm and then suddenly the boat took
off like a bat out of hell running at 8000 rpms and 25mph??? I never
touched the throttle. It has never run that fast ever. After about 2
minutes it went back down to 5500 and never did 8000 again. Its a
60hp mercury Bigfoot outboard. It has never done this before and I
don't even know how it could rev that high and go 25mph. Normal is
5500 and 17mph. What happened??

Mike


The boat wouldn't go faster if the prop was spun.

5000 - 8000 RPM Surprise
 

John H wrote:
On Mon, 15 Jun 2009 10:00:18 -0400, "Reginald P Smithers III, Esq."
wrote:

John H wrote:
On Mon, 15 Jun 2009 07:50:33 -0400, "Reginald P Smithers III, Esq."
wrote:

Mike Slater wrote:
"Eisboch" wrote in message
...
"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real
surprise. Somebody please tell me how and why I could be running wide
open throttle at my normal 5500 rpm and then suddenly the boat took
off like a bat out of hell running at 8000 rpms and 25mph??? I never
touched the throttle. It has never run that fast ever. After about 2
minutes it went back down to 5500 and never did 8000 again. Its a
60hp mercury Bigfoot outboard. It has never done this before and I
don't even know how it could rev that high and go 25mph. Normal is
5500 and 17mph. What happened??

Mike
Is it a two stroke? I've often noticed on 2 stroke weed wackers or
chain saws that just as you are about to run out of fuel they speed
up. I think they start running lean due to air in the fuel line.
Is it possible you had a temporary air leak in a line and a similar
thing is happening?

Eisboch

Yep. Its a two-stroke. It really caught me by surprise. Next time I
will look at the clear inline gas filter down near the primer bulb to
see if its empty if and when it happens. It was only my second outing
this year so who knows what going on and was too shocked to think about
looking at the fuel situation. You know, it sounded great at 8000 revs.
Mike,
You may want to consider dropping back to a "cruising" rpm, instead of
running it WOT. Running the boat at WOT will shorten the life of the
engine considerably and use about 3 times the gas. For most boats, the
best gph or mpg is about 3400-3600 rpm. You shouldn't pick up much
incremental speed at WOT.
I ran mine at WOT yesterday, for the first time. Only did it for about
15 seconds. Man, that little boat is fast!
--
John H

"The democracy will cease to exist when you take away from those
who are willing to work and give to those who would not."
Thomas Jefferson
That sound of the wind whistling in your ears, was really the sound of
the engine sucking down the gas. ;)

That's another reason I usually hold it to 3400. It seems to be happy
there.
--
John H

"The democracy will cease to exist when you take away from those
who are willing to work and give to those who would not."
Thomas Jefferson

Trimmed up?

5000 - 8000 RPM Surprise
 

JR North wrote:
Didn't read the post right. The 'normal' speed was ambiguously unclear
and out of place in the text.
JR


Loogypicker wrote:

On Jun 14, 9:01 pm, JR North wrote:

Your prop hub is slipping. Get the prop rebuilt.
JR
BTDT got the T-shirt, too


If the prop was slipping it wouldn't go from the normal 17mph @ 5500
RPM to the 25mph at 8k.


Can you imagine if he top posted? Everyone else might have come to the
same conclusion as you.

5000 - 8000 RPM Surprise
 

"DK" wrote in message
...
Eisboch wrote:
"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real surprise.
Somebody please tell me how and why I could be running wide open
throttle at my normal 5500 rpm and then suddenly the boat took off like
a bat out of hell running at 8000 rpms and 25mph??? I never touched the
throttle. It has never run that fast ever. After about 2 minutes it
went back down to 5500 and never did 8000 again. Its a 60hp mercury
Bigfoot outboard. It has never done this before and I don't even know
how it could rev that high and go 25mph. Normal is 5500 and 17mph.
What happened??

Mike


Is it a two stroke? I've often noticed on 2 stroke weed wackers or
chain saws that just as you are about to run out of fuel they speed up.
I think they start running lean due to air in the fuel line.
Is it possible you had a temporary air leak in a line and a similar thing
is happening?

Eisboch

For two minutes? I can't believe 8000 rpms didn't blow it up!

My boat runs comfortably at 10,000 rpm. g

--Mike

5000 - 8000 RPM Surprise
 

On Mon, 15 Jun 2009 20:08:41 -0400, D K
wrote:

John H wrote:
On Mon, 15 Jun 2009 10:00:18 -0400, "Reginald P Smithers III, Esq."
wrote:

John H wrote:
On Mon, 15 Jun 2009 07:50:33 -0400, "Reginald P Smithers III, Esq."
wrote:

Mike Slater wrote:
"Eisboch" wrote in message
...
"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real
surprise. Somebody please tell me how and why I could be running wide
open throttle at my normal 5500 rpm and then suddenly the boat took
off like a bat out of hell running at 8000 rpms and 25mph??? I never
touched the throttle. It has never run that fast ever. After about 2
minutes it went back down to 5500 and never did 8000 again. Its a
60hp mercury Bigfoot outboard. It has never done this before and I
don't even know how it could rev that high and go 25mph. Normal is
5500 and 17mph. What happened??

Mike
Is it a two stroke? I've often noticed on 2 stroke weed wackers or
chain saws that just as you are about to run out of fuel they speed
up. I think they start running lean due to air in the fuel line.
Is it possible you had a temporary air leak in a line and a similar
thing is happening?

Eisboch

Yep. Its a two-stroke. It really caught me by surprise. Next time I
will look at the clear inline gas filter down near the primer bulb to
see if its empty if and when it happens. It was only my second outing
this year so who knows what going on and was too shocked to think about
looking at the fuel situation. You know, it sounded great at 8000 revs.
Mike,
You may want to consider dropping back to a "cruising" rpm, instead of
running it WOT. Running the boat at WOT will shorten the life of the
engine considerably and use about 3 times the gas. For most boats, the
best gph or mpg is about 3400-3600 rpm. You shouldn't pick up much
incremental speed at WOT.
I ran mine at WOT yesterday, for the first time. Only did it for about
15 seconds. Man, that little boat is fast!
--
John H

"The democracy will cease to exist when you take away from those
who are willing to work and give to those who would not."
Thomas Jefferson
That sound of the wind whistling in your ears, was really the sound of
the engine sucking down the gas. ;)

That's another reason I usually hold it to 3400. It seems to be happy
there.
--
John H

"The democracy will cease to exist when you take away from those
who are willing to work and give to those who would not."
Thomas Jefferson

Trimmed up?

Nicely!


--
John H

"The democracy will cease to exist when you take away from those
who are willing to work and give to those who would not."
Thomas Jefferson

5000 - 8000 RPM Surprise
 

On Jun 15, 5:22*pm, JR North wrote:
Didn't read the post right. The 'normal' speed was ambiguously unclear
and out of place in the text.
JR

10-4!

Loogypicker wrote:
On Jun 14, 9:01 pm, JR North wrote:

Your prop hub is slipping. Get the prop rebuilt.
JR
BTDT got the T-shirt, too

If the prop was slipping it wouldn't go from the normal 17mph @ 5500
RPM to the 25mph at 8k.

--
--------------------------------------------------------------
* * * * Home Page:http://www.seanet.com/~jasonrnorth

5000 - 8000 RPM Surprise
 

mgg wrote:
"DK" wrote in message
...
Eisboch wrote:
"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real surprise.
Somebody please tell me how and why I could be running wide open
throttle at my normal 5500 rpm and then suddenly the boat took off like
a bat out of hell running at 8000 rpms and 25mph??? I never touched the
throttle. It has never run that fast ever. After about 2 minutes it
went back down to 5500 and never did 8000 again. Its a 60hp mercury
Bigfoot outboard. It has never done this before and I don't even know
how it could rev that high and go 25mph. Normal is 5500 and 17mph.
What happened??

Mike

Is it a two stroke? I've often noticed on 2 stroke weed wackers or
chain saws that just as you are about to run out of fuel they speed up.
I think they start running lean due to air in the fuel line.
Is it possible you had a temporary air leak in a line and a similar thing
is happening?

Eisboch
For two minutes? I can't believe 8000 rpms didn't blow it up!

My boat runs comfortably at 10,000 rpm. g

--Mike



Your pontoon with a 60hp Merc Bigfoot? Nice!

5000 - 8000 RPM Surprise
 

"Mike Slater" wrote in message
news:knfZl.742458$yE1.158636@attbi_s21...
I was cruising along in my 24ft pontoon boat when I got a real surprise.
Somebody please tell me how and why I could be running wide open throttle
at my normal 5500 rpm and then suddenly the boat took off like a bat out of
hell running at 8000 rpms and 25mph??? I never touched the throttle. It
has never run that fast ever. After about 2 minutes it went back down to
5500 and never did 8000 again. Its a 60hp mercury Bigfoot outboard. It
has never done this before and I don't even know how it could rev that high
and go 25mph. Normal is 5500 and 17mph. What happened??

Mike
I wanted to try to close the loop on this issue and I think I can. I think
as someone stated, running "lean" can cause the engine to rev higher. I
looked at my inline fuel filter and the thing was empty when it did it
again. Today I replaced all the fuel lines to make sure no air was getting
in and it has not happened since. I am back to 17mph. BTW, I don't trust
the tach reading of 8,000 that I got because the reading is a little
"unsteady" despite no discernable (by ear) engine rpm changes.

I know that running lean can burn the pistons so whoever mentioned running
out of fuel (lean) as being something to check... THANKS.

Mike