IO Low RPM "Thumping"
 

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last summer
I noticed that "on occasion" that boat would seem to "thump" after putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some at
middle RPM's. When I have it full open, it seems to be working just fine.

Anybody ever had this, or heard of it, or have any idea what it might be? I
know you can't diagnose over the net, but maybe the symptoms sound familiar.

Thanks!

IO Low RPM "Thumping"
 

I can't comment on what it is - but spooky that I just had a similar thump at
lower RPM's today -- to the point that I left the wheel & walked back looking
for something stuck to the boat & whacking it....
I lifted the engine compartment & didn't hear anything.

I'm worring that there's an outdrive issue.

On Wed, 14 Jun 2006 00:50:57 GMT, "Larry" wrote:

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last summer
I noticed that "on occasion" that boat would seem to "thump" after putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some at
middle RPM's. When I have it full open, it seems to be working just fine.

Anybody ever had this, or heard of it, or have any idea what it might be? I
know you can't diagnose over the net, but maybe the symptoms sound familiar.

Thanks!



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IO Low RPM "Thumping"
 

Larry wrote:

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last summer
I noticed that "on occasion" that boat would seem to "thump" after putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some at
middle RPM's. When I have it full open, it seems to be working just fine.

Anybody ever had this, or heard of it, or have any idea what it might be? I
know you can't diagnose over the net, but maybe the symptoms sound familiar.

Thanks!



U-joints.

Rob

IO Low RPM "Thumping"
 

"trainfan1" wrote in message
et...
Larry wrote:

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last
summer
I noticed that "on occasion" that boat would seem to "thump" after
putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it
would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some
at
middle RPM's. When I have it full open, it seems to be working just
fine.

Anybody ever had this, or heard of it, or have any idea what it might
be? I
know you can't diagnose over the net, but maybe the symptoms sound
familiar.

Thanks!



U-joints.

U-joints "thump" ? What was the "rate" of the thump? And what is the RPM?
I would think the term used would be more like "vibration" - "thump" implies
that its not following the rate of the turning drive shaft.





Rob

IO Low RPM "Thumping"
 

"Larry" wrote in message
news:R3Jjg.1021435$xm3.420552@attbi_s21...
Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last
summer

I noticed that "on occasion" that boat would seem to "thump" after putting
it in gear.

The initial "thump" when putting it in gear is normal. That is he dog clutch
engaging. So is this thump after that initial drive engagement thump? If
so, do it sound the same ?


If I stayed at low RPM while leaving the boat ramp, it would
"thump" every few seconds.

Then thats not U-joints - sounds like it may be coming in/out
of gear perhaps? Have you checked shifter cables etc ?
Also, might be that interupter switch thing that cuts out the
iginition when you go in/out of gear, and cross over to reverse.
Is this an Alpha drive? Or god forbid a Cobra drive ?

IO Low RPM "Thumping"
 

U-joints "thump" ? What was the "rate" of the thump? And what is the RPM?
I would think the term used would be more like "vibration" - "thump" implies
that its not following the rate of the turning drive shaft.

For me it was a resounding "THUMP" every few seconds, at about 1000-2000 RPM,
went up to 3500 it went away; went back down; didn't happen again.


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IO Low RPM "Thumping"
 

Then thats not U-joints - sounds like it may be coming in/out
of gear perhaps? Have you checked shifter cables etc ?
Also, might be that interupter switch thing that cuts out the
iginition when you go in/out of gear, and cross over to reverse.
Is this an Alpha drive? Or god forbid a Cobra drive ?

Mine is a cobra -- whack me with the bad news while the boat is out... G

I think I have an electrical (new boat to me) as the cut out is kicking in when
I hit the trim. It also will let me trim it into trailer mode while underway --
I know; off topic thread.....

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IO Low RPM "Thumping"
 

"Josh Assing" wrote in message
...
U-joints "thump" ? What was the "rate" of the thump? And what is the
RPM?
I would think the term used would be more like "vibration" - "thump"
implies
that its not following the rate of the turning drive shaft.

For me it was a resounding "THUMP" every few seconds, at about 1000-2000
RPM,
went up to 3500 it went away; went back down; didn't happen again.

A fricking "U" joint did this?.... 'who knew'.
Dang, learn something new every day. I
don't unserstand the mechanics behind that
unless it causes some sort of binding or something ?




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IO Low RPM "Thumping"
 

"Mr Wizzard" wrote in message
. ..


A fricking "U" joint did this?.... 'who knew'.
Dang, learn something new every day. I
don't unserstand the mechanics behind that

Wait!, you;re not the one suggesting U-joints,
you're the original problem poster. So yeah..
Every "few seconds" isn't U-joints, I just don't
buy that. I'm thinking engine alignment, binding,
coupler, dog-clutch coming disengaged, or
something like that. So tell me, does it sould
the same as the "clunk" (or thump as you say)
you get when putting it in gear? When was the
last time the shifter cable on your Coba replaced?
The 89-ish Cobra's shifter mechanism gets very
"vague" with old/stretched shifter cables. Also,
and so you know, this is a "shift lever" retrofit,
or upgrade that OMC had for that year. (this
device is inside the lower unit.






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IO Low RPM "Thumping"
 

Sounds like a shift cable issue.Take it to a dealer to make sure you have
the most refined shift cable installed. (They(OMC) "improved" the cable
setup several times before it would work right.)
"Josh Assing" wrote in message
...
Then thats not U-joints - sounds like it may be coming in/out
of gear perhaps? Have you checked shifter cables etc ?
Also, might be that interupter switch thing that cuts out the
iginition when you go in/out of gear, and cross over to reverse.
Is this an Alpha drive? Or god forbid a Cobra drive ?

Mine is a cobra -- whack me with the bad news while the boat is out... G

I think I have an electrical (new boat to me) as the cut out is kicking in
when
I hit the trim. It also will let me trim it into trailer mode while
underway --
I know; off topic thread.....

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