1995 FORCE 75 hp what are splines at top of driveshaft connected to? Flywheel?

[surfsalterpath]

I am trying to narrow down the cause of intermittent "bang" or "THUMP" to my 1995 FORCE 75hp engine 20" driveshaft.
When I get 2000 rpms of higher a "THUMP" vibrates and shakes the whole engine and thus the whole pontoon boat, a 24' Spectrum.

I removed the lower unit, drained the gear lube and turned the driveshaft gingerly looking for any sign of gear issues. The shifter, after I adjusted over and over now shifts the BEST it ever has! NO grinding and very smooth! Could not find a problem. Water pump has a strong stream peeing good.

So now I am thinking whatever the top of the driveshaft splines insert into (is it the flywheel)?? when it is inserted into that dark cavity to nowhere? ha ha ...... might be slipping and causing this THUMP or BANG that vibrates the whole boat and you can physically see the engine jump. ONLY happens when the engine is 2000 rpm or higher. Faster rpms, is: 3000 - 5000 rpms the THUMPS are like THUMP ........ Thump ....... THUMP ..... etc. More oftem lower rpms further apart.

Before I re-installed the lower unit we inspected the splines at the top of the driveshaft for wear and tear and saw NONE at all! The splines look as good as they would be when new. No wear and tear.

Perplexed!

THANKS!
ssp

 

[foodfisher]

Worn/rounded dog ears?

 

[racerone]

??-----The splines go into the crankshaft splines.------The flywheel is attached at the other end of the crankshaft.-----Check gear oil in the lower unit.

 

[foodfisher]

Oops, can't find edit button. Just dogs, no ears.

 

[surfsalterpath]

.....drained the lower unit gearbox very good and put new gear lube 80-90w back in.
No milky oil nor any metal shavings that I could see. Re-installed the lower unit
for another test run.

I have not pulled the crankshaft which I guess it is attached to the flywheel. That is
probably out of my mechanical abilities and also the $$$ would be more than
I would want to spend on a 1996 engine. SO if the "driveshaft" connection to
the "crankshaft" is worn then I'm going to have to sell the engine for parts.
RATS! I've already bought the $600 freshwater 75hp FORCE lower unit!

An auto mechanic Friend that has helped me on the boat a lot thru the years rode
w/ me yesterday and we re-enacted the THUMPS. He said he thought it was the
engine missing. Hard for me to tell exactly where the THUMPS are coming from
but when they occur the engine is above 2000 rpm and we are underway on the water.
When the THUMP occurs you can see the engine jump and it vibrates thru the whole boat.

The THUMP is pretty intense and is kind scary sounding because it kinda feels like
the engine will jump off the transom! Sometimes the THUMPS are louder/more intense
than at other times. The timing of the THUMP is random also.

THANKS!

 

[surfsalterpath]

.....anyone have a miracle fix for the "driveshaft to crankshaft" connection
for the FORCE 1995 75 hp engine? ha ha!

 

[RCO]

The driveshaft connection to the crankshaft is fine. If it wasn't, the motor would not move at all. The rare times they fail is usually from hitting an obstruction at high speed and will strip the splines off the shaft, or more likely break the top of the shaft right off.
The most likely issue is the clutch dog and/or its mating surfaces on the gears in the lower unit. I would especially be concerned about that since you mention grinding before you adjusted the linkage.

 

[surfsalterpath]

.... THANKS! THAT sounds PROMISING!
Maybe there is hope then ..... with the used fresh water lower unit I should receive Friday.
If we can get a couple more years out of this workhorse I'd be happy! All our Friends
on our canal cannot believe this FORCE is "still running" ha ha!

I'll keep you posted!

ssp

 

[Nordin]

Foodfisher and RCO are on it.
The clutch is worn, the edges are rounded at the dog and at the forward gear.

If you are lucky the shifting is not right adjusted.
BUT I think it is the clutch dog.

 

[surfsalterpath]

....THANKS!

I was able to get the shift adjusted so there is NO grinding or rattling noise going into forward
or reverse. Best shift it has been since I have owned the pontoon!!! Smooth as silk. It took a while
but I figured out how to fine tune the shifter at the shift rod bolt you have to undo to remove the
lower unit.

I just think after all these years of it not shifting smoothly has taken a toll on the "clutch dog."
Sadly, several of those gearing pieces are not available on "MarineEngine" and the parts that
are so expensive I think it would cost me about $400 to repair if I do it myself. If I can find a
clutch dog I might order so I can try to rebuild those gears so I can have 2 lowers ready to go.

The engine is running very smooth right now so I hate to ditch it just yet. Fingers crossed this
freshwater lower is in good shape!

THANKS!!!!!!

 

[jerryjerry05]

Most make the mistake of shifting slowly into gear.
It should be a fairly fast and smooth into gear.

You sure it's a 75-95 ??
A 70 is listed for parts????

If the splines on the drive shaft and crank were stripped, you wouldn't have any movement
of the drive shaft(you ain't going nowhere)

Over time, your right the dog can be bad by now.

The dog can be flipped and the other side used.
Some use a dremel and make squared off edges.
Use the fixed side for reverse.

The part is NLA
Even e-bay doesn't seem to have one??
So dremel the old, or machine shop.

 

[surfsalterpath]

THANKS!

You are correct about the '95 or '96! Our 75hp FORCE serial# is #OE139378 and on some searches shows it is a '96 or shows not available. The Wildlife Registration card has our pontoon listed as 1995. There could be a mistake, I guess. For sure, the 75hp FORCE is either a 1995 or a 1996. marineengine & iBoats parts have it listed but most lower unit gearing parts are unavailable on these sites.

Thanks for the tip on "flipping the clutch dog" !!! That would be an interesting hack!!!!

I have my fingers crossed this fresh water lower will get us back on the water for at least this season ~

Have a GREAT day!

 

[surfsalterpath]

Well, we got the "new" USED lower unit installed and it runs GREAT! So far, knock on wood! Thanks for all your advice and guiding this mechanical neophyte thru a challenging, learning and FUN time!

Now if I can find a "clutch dog" and the bearings/seals I might try to attempt the gear rebuild. That would be interesting!
I'd be nice to have a back up @ the ready.

 

[jerryjerry05]

The bearings and seals are available.
The dog, new isn't available.
Try Franz Marine. Seems he's good at pulling rabbits out of the hat

 

[surfsalterpath]

THANKS! Sent Franz Marine an email in search of a CLUTCH for my 1995 FORCE 75hp! [h=1]52-817463 - CLUTCH[/h] http://www.hurrikain.com/Franzmarine/

 

[surfsalterpath]

YEA! Franz pulled ANOTHER "rabbit out of the hat" !!
Franz said he gets lots of referrals from iBoats! But has never been on the page.
I gave him your screen name jerryjerry05 - Franz said thank you!

And I appreciate you pointing me Franz's way. He said it would be tough to get the
"yoke" back on the "lower shirt rod arm assembly" his tip - use grease on the 2 tips of the yoke
yo hold yoke in place.

This is going to be fun.

 

[surfsalterpath]

Franz had the clutch dog and I ordered the O-Ring ...... in case I have to use heat
on the carrier removal! Another "rabbit pulled out of the hat" by Franz !!
Franz said THANKS for the referral!

Now, IF I can get that (been in salt water since 1996) carrier housing assembly off,
and IF the gears look good and IF I can get that "yoke" back on the lower shift rod arm assembly
(Franz said use grease to hold the yoke in place)
then maybe, just maybe we'll have a backup lower unit ready to go w/ a $200 gamble!

 

[jerryjerry05]

The carrier held in by 2 screws.
Start spraying with PB Blaster or Krol.
Then a 2 jaw puller with 2 hooks to reach in and hook the arms.

I made my own arms.
I bent the ends of a threaded rod and heat treated the ends.

As you pull the carrier, heat the outside of the case and apply pressure on the puller.

An acetylene torch comes in handy, but the alum. can melt easily.

 

[surfsalterpath]

Sorry for the duplicate posts. Did not see they posted on page 2. Oh my!
Thanks for the advice!