Why does OB motor "buck" in mid-full FWD throttle? 9.9hp Chrysler Seaking '83

[CigarXO]

Why does OB motor "buck" in mid-full FWD throttle? 9.9hp Chrysler Seaking '83

Took the "new to me" old Chrysler OB out for its first test spin. It cranks 1-2 pull. It idles okay. It putts along at a slow troll speed okay. BUT, when I increase to middle-top of forward throttle it starts to buck. I tried two motor angles and motor sits well down in the water due to me being in back of boat near tiller. ???

Here's a video: http://youtu.be/ssrAgfFjo7s

 

[Frank Acampora]

Unfortunately I have bad news: The drive dogs inside the lower unit are worn and the engine is slipping in and out of gear at high power. This will only get worse the longer you run the engine.

Either disassemble the lower unit and dress the drive dogs on the dog clutch and forward gear to square again or try to find a compatible used lower unit. Depending upon the year, A Chrysler 9.9-15 lower unit may fit.

 

[CigarXO]

Unfortunately I have bad news: The drive dogs inside the lower unit are worn and the engine is slipping in and out of gear at high power. This will only get worse the longer you run the engine.

Either disassemble the lower unit and dress the drive dogs on the dog clutch and forward gear to square again or try to find a compatible used lower unit. Depending upon the year, A Chrysler 9.9-15 lower unit may fit.

Frank et al,

1. I disassembled the lower unit (nothing to lose). First one, so I was surprized with how small the gears, clutch, pinion are on this little engine (I'm usually playing under a Jeep.) If I wasn't looking for it, I would have thought the dog and matching gear cogs were fine. Then I noticed by comparison the load bearing sides of each cog (clutch & gear) are slightly rounded vs a very square non-contacting surface. You mentioned "Squaring". Will a local machine shop do this work? It's too delicate for any tools I have.

2. Things don't look too bad. I believe the lower water pump seal needs replacing as I'm seeing corrosion, so my plan is to order water pump impeller and seal kits for pump, shaft and gear while I'm in here. Is there anything else?

3. I have noticed the fresh lower gear oil sipping from the upper (mid section) tiny vent hole - not, the upper fill/drain vent, but what I think is water/oil drainage site. Some write-ups say its over-fill (possible since I just changed); some suggest gear shift shaft seal (which will be changed with seal kit); and some say normal for engine sitting as this one has. Any thoughts/checks I should make?

Thanks,
CigarXO

 

[Frank Acampora]

You don't need a machine shop--they will charge more than a used lower unit would cost. A Dremel and straight carbide bit will do it just fine by hand if you are methodical and careful.

 

[jerryjerry05]

Try turning it around.
You usually don't rev the motor too much in reverse.
The dog is usually the same on both sides.
Or you can buy another.

35

F99521-1

CLUTCH boats . net

$84.63

 

[CigarXO]

Jerry,
Looked at turning it around as I saw that idea on a thread. On closer inspection, it may have been done as both drive clutch and gears F&R show almost equal wear. I've identified parts/providers to order, but first I'm going to grind the cogs and see if that will get her running because I also want to inspect the top end of this engine more as I'm finding corrosion on the bottom end and wonder if Grandpa had this out in the Puget Sound/salt. This engine may not be worthy of more parts.

Frank,
So, I used the Dremel. It's a tough thing to do as now 12 surfaces/angles come into play. I now plan to give it a test, which has left me with a few re-assembly issues: (though a puzzle, I think I have the lower unit together and functional.)

1. Before attaching the lower unit, and therefore not having the F/N/R shift rod completely assembled, I'm having difficulty insuring I have play to achieve F/N/R using just the lower shaft attached to the pinion lever. Any wisdom on adjusting the shift rod before I button it up? Which way does the drive shaft rotate when driven by the engine?

2. I'll be opening her up again after testing the resurfaced gears as the lower water pump seal seems bad. I'll use a seal kit then - and order gears if these don't test well.

3. Here's my project boat to date: http://youtu.be/B0b-S6A9NE8

Thanks,
CigarXO

 

[CigarXO]

I tested the dremelled gears and though it worked great in the trash can, the engine still slips under load on the lake. I ordered a new dog clutch and "front" gear - yet to install. Them I realized FRONT does not necessarily equal FORWARD gear. From a perspective of the front of the gear pinion, is the front gear cog also the forward gear???

 

[Frank Acampora]

The gear closes to the nose of the gearcase is forward gear. Reverse is closes to the prop..

 

[CigarXO]

Frank - Great, thanks!
So Front does equal Forward and Rear equals Reverse. At $100, I only wanted to buy the Forward gear as I have no issue with the slow speeds of reverse even though the clutch and cog showed similar wear as forward. I woke-up a few days after I ordered in a cold sweat afraid I'd wasted $100 on reverse and still needed another...

 

[CigarXO]

No Title

I pulled a "rookie" boater "Ah, $#!?" yesterday. After replacing my clutch and forward lower unit gears, I finally got the 9.9 SeaKing and boat (with 3 daughters) back on the lake. It was a wonderful fall day in WA. The repaired drive operated well out to a spot from which I started using my Minn Kota. We stayed too long and as sunset arrived and I hurriedly coordinated our cruise back to the boat ramp - I left the 10# bell anchor in the water. For the first hundred yards, the engine again slipped gears and I thought my repair had failed. Then I noticed the anchor. Unfortunately, the motor continued to slip the rest of the way in. I'm sure I'll have to disassemble the lower unit again to diagnose, but is there any other part I should be looking at/replacing - like the spring on the pin in the pinion?