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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IO Low RPM "Thumping"
 

the same as the "clunk" (or thump as you say)
you get when putting it in gear? When was the

no; it goes in and out of gear w/o an issue -- it's very crisp and prompt.

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.

I'm going with original - the PO had a lot of notes about what was done; and I
don't see any retrofit (this is a 90; so that counts as 89ish)

-josh


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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.)

hehe -- OK -- thanks.
-j

"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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IO Low RPM "Thumping"
 

"Jim" wrote in message
nk.net...
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.)

Yup, specifically, the "shift lever" retrofit which involves
a lever (and associated bushings etc) inside the lower unit.
But that assumes that the source of his clunking (thumping)
is his gear unit coming in/out of drive (at low speed).

Problem is, unless he figures it out on his own (and/or with
the help of the newgroup here), if he takes it in to a OMC
authorized repair joint, you know how its going to go down:
1990 Cobra? humm, Ok Mr Jones, so I got you down for:
new shifter cables, the shift "lever" retrofit inside the unit,
U-joints, gimbal bearing, boots, bellows, engine alignment,
and oh yeah, and we'll change the oil for ya too! Thing is,
probably needs all of that anyways, but summer's just
starting, so the shops are going to be busy, and your boat
may be layed up in some shop for a while. What area ?



"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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IO Low RPM "Thumping"
 

There aren't many folks around that will admit to being Cobra experts. I
remember looking at the shift lever on one once. If I remember correctly, It
wouldn't be too difficult to clean up the area that gunked up with salt. The
retrofit probably had to do with loosening up the clearance between the
lever and bushings so that the salt buildup wouldn't cause things to bind
up. The cable problem probably had to do with figuring out how to tighten up
the slop without having the cable bind. No person that wasn't being
reimbursed with warranty money would want to take ownership of these
problems.
JMHO
Jim

"Mr Wizzard" wrote in message
. ..

"Jim" wrote in message
nk.net...
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.)

Yup, specifically, the "shift lever" retrofit which involves
a lever (and associated bushings etc) inside the lower unit.
But that assumes that the source of his clunking (thumping)
is his gear unit coming in/out of drive (at low speed).

Problem is, unless he figures it out on his own (and/or with
the help of the newgroup here), if he takes it in to a OMC
authorized repair joint, you know how its going to go down:
1990 Cobra? humm, Ok Mr Jones, so I got you down for:
new shifter cables, the shift "lever" retrofit inside the unit,
U-joints, gimbal bearing, boots, bellows, engine alignment,
and oh yeah, and we'll change the oil for ya too! Thing is,
probably needs all of that anyways, but summer's just
starting, so the shops are going to be busy, and your boat
may be layed up in some shop for a while. What area ?



"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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Remove X's to send email to me.

IO Low RPM "Thumping"
 

"Jim" wrote in message
nk.net...
There aren't many folks around that will admit to being Cobra experts. I
remember looking at the shift lever on one once. If I remember correctly,
It
wouldn't be too difficult to clean up the area that gunked up with salt.
The
retrofit probably had to do with loosening up the clearance between the
lever and bushings so that the salt buildup wouldn't cause things to bind
up. The cable problem probably had to do with figuring out how to tighten
up
the slop without having the cable bind. No person that wasn't being
reimbursed with warranty money would want to take ownership of these
problems.
JMHO
Jim

True on the clanup, but the retrofit was actually a reesigned
shift lever (physical part) to be replaced. And I think there
were actually 6 cable redesign's in total (for all Cobra's)





"Mr Wizzard" wrote in message
. ..

"Jim" wrote in message
nk.net...
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.)

Yup, specifically, the "shift lever" retrofit which involves
a lever (and associated bushings etc) inside the lower unit.
But that assumes that the source of his clunking (thumping)
is his gear unit coming in/out of drive (at low speed).

Problem is, unless he figures it out on his own (and/or with
the help of the newgroup here), if he takes it in to a OMC
authorized repair joint, you know how its going to go down:
1990 Cobra? humm, Ok Mr Jones, so I got you down for:
new shifter cables, the shift "lever" retrofit inside the unit,
U-joints, gimbal bearing, boots, bellows, engine alignment,
and oh yeah, and we'll change the oil for ya too! Thing is,
probably needs all of that anyways, but summer's just
starting, so the shops are going to be busy, and your boat
may be layed up in some shop for a while. What area ?



"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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IO Low RPM "Thumping"
 

I just got to reading the replies and I thank everyone.

Couple things...I am certainly not a boat expert so there are lots of things
I didn't know one shouldn't do. One of them is run the boat with the
outboard in the up position. Many times we lift it up in the shallow water
to where the prop is just below the waterline to give it some thrust. I now
see thats a no no, and it seems I could have damaged my u joints right
there.

As far as the "thumping", thats the best I could describe it. It's
certainly not a continuous vibration. It almost sounds as if someone were
below the boat and pounded their fist into the hull. When we were running
yesterday at half speed, it almost seemed like I could predict when a thump
would occur. Just about every five seconds...thump...five more
seconds...thump. Not exactly, but pretty close. The thumping starts
immediately upon shifting into forward gear, (don't recall if it happens in
reverse) and is almost continuous now at low rpm's. It's way worse than
last year when it only occurred a few times at low rps's. Obviously, it's a
progressive problem that is getting worse.

I'm taking it into a marina tomorrow. They're about a week out on the
service calls, or so they say. I'm hoping they'll just put it in the water,
hear the thumps, tell me I needed some new transmission fluid, and off I go.
I know it's a far out chance, but that's what I'm hoping for. G

Yes, it's an OMC Cobra. I assume it's a 1986 because that is the year of
the boat. I paid $5000 for the boat and trailer last summer (probably a tad
too much) but it's given us some fun. If the repair bill is going to cost
to much, I'm not sure what my options are. I really don't want to put a lot
of money into such an old boat. I wonder if I'm better off taking my
medicine and buying another used boat with an outboard. The kids are into
tubing and skiing. It's simply used for recreational water sport.

..Larry

IO Low RPM "Thumping"
 

On Wed, 14 Jun 2006 21:03:46 GMT, "Larry" wrote:

Many times we lift it up in the shallow water
to where the prop is just below the waterline to give it some thrust. I now
see thats a no no, and it seems I could have damaged my u joints right
there.

You can't run much above idle speed without damaging the U-joints if
the drive is tilted up. My manual says less than 1,000 RPM.

IO Low RPM "Thumping"
 

Did you check your bottom end fluid? When I had an intermittent "thumping"
in my merc, I lost the "lower unit" before I could slowly get back to the
launch. It was the dog gear jumping out from time to time. It "only" cost
me a thousand $.
LD

"Larry" wrote in message
news:SQ_jg.1023457$xm3.983052@attbi_s21...
I just got to reading the replies and I thank everyone.

Couple things...I am certainly not a boat expert so there are lots of
things
I didn't know one shouldn't do. One of them is run the boat with the
outboard in the up position. Many times we lift it up in the shallow
water
to where the prop is just below the waterline to give it some thrust. I
now
see thats a no no, and it seems I could have damaged my u joints right
there.

As far as the "thumping", thats the best I could describe it. It's
certainly not a continuous vibration. It almost sounds as if someone were
below the boat and pounded their fist into the hull. When we were running
yesterday at half speed, it almost seemed like I could predict when a
thump
would occur. Just about every five seconds...thump...five more
seconds...thump. Not exactly, but pretty close. The thumping starts
immediately upon shifting into forward gear, (don't recall if it happens
in
reverse) and is almost continuous now at low rpm's. It's way worse than
last year when it only occurred a few times at low rps's. Obviously, it's
a
progressive problem that is getting worse.

I'm taking it into a marina tomorrow. They're about a week out on the
service calls, or so they say. I'm hoping they'll just put it in the
water,
hear the thumps, tell me I needed some new transmission fluid, and off I
go.
I know it's a far out chance, but that's what I'm hoping for. G

Yes, it's an OMC Cobra. I assume it's a 1986 because that is the year of
the boat. I paid $5000 for the boat and trailer last summer (probably a
tad
too much) but it's given us some fun. If the repair bill is going to cost
to much, I'm not sure what my options are. I really don't want to put a
lot
of money into such an old boat. I wonder if I'm better off taking my
medicine and buying another used boat with an outboard. The kids are into
tubing and skiing. It's simply used for recreational water sport.

.Larry

IO Low RPM "Thumping"
 

For me -- it has new oil, boots, bellows, alightment, gimbla & ujoints.
and it's not popping in and out of gear, I'd feel that -- no loss of speed, or
jerkyness in the boat

Tacoma area Washington state.
On Wed, 14 Jun 2006 08:39:54 -0700, "Mr Wizzard" wrote:


"Jim" wrote in message
ink.net...
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.)

Yup, specifically, the "shift lever" retrofit which involves
a lever (and associated bushings etc) inside the lower unit.
But that assumes that the source of his clunking (thumping)
is his gear unit coming in/out of drive (at low speed).

Problem is, unless he figures it out on his own (and/or with
the help of the newgroup here), if he takes it in to a OMC
authorized repair joint, you know how its going to go down:
1990 Cobra? humm, Ok Mr Jones, so I got you down for:
new shifter cables, the shift "lever" retrofit inside the unit,
U-joints, gimbal bearing, boots, bellows, engine alignment,
and oh yeah, and we'll change the oil for ya too! Thing is,
probably needs all of that anyways, but summer's just
starting, so the shops are going to be busy, and your boat
may be layed up in some shop for a while. What area ?



"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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