'83 OMC 2.5L Stalling/Idel issues

[Cromagnon35]

First post for this new boater, please be kind ;-)

I've purchased a 1983 Penn Yan Game and Fish 18 with a 2.5L OMC stern drive and have been having a hard time getting it to run consistently well.

It was abused a bit over the last winter (at least) having been left out, uncovered, in the heavy snow and I believe it filled up with water and froze.

Immediately apparent that it was waterlogged, I:

changed the oil (mostly water) ran it for a few min and changed again.
Drained the gas tank and refilled with 87 octane.
Replaced a freeze plug that gave out on it's first launch (checked - oil is perfect, no water).
Tuned up with new dist. cap and rotor, plugs, wires, Carb Kit (2bbl Rochester 2gc), fuel filter, points and timing.

Engine starts easilly and runs fairly smooth for a few minutes then loses RPM's and dies and/or loses power. Restarting is sometimes difficult, but seems to work best with throttle set at idle.

To me it seems the issue is related to the warmup -
* Could it be the choke? is there a trusty way to set the Choke? This carb seems to use an air/thermal choke, which I'm unfamiar with.

* Might there still be water getting to the gas? Would it be worth putting a fuel/water seperator filter in?

* Could it be the coil? the one on it came with the boat.

The big boss (wife) is getting tired of me throwing money at it and I need to be a bit more selective on what I apply funds to.

The boat is otherwise in great shape and is the best riding/handling in this size class I've been in, it'd be a waste for me to let 'er go.

Help!

 

[capthook]

Re: '83 OMC 2.5L Stalling/Idel issues

First post for this new boater, please be kind ;-)

I've purchased a 1983 Penn Yan Game and Fish 18 with a 2.5L OMC stern drive and have been having a hard time getting it to run consistently well.

It was abused a bit over the last winter (at least) having been left out, uncovered, in the heavy snow and I believe it filled up with water and froze.

Do a compression check first to make sure that there is not any leakage

Immediately apparent that it was waterlogged, I:

changed the oil (mostly water) ran it for a few min and changed again.
Drained the gas tank and refilled with 87 octane.
Replaced a freeze plug that gave out on it's first launch (checked - oil is perfect, no water).
Tuned up with new dist. cap and rotor, plugs, wires, Carb Kit (2bbl Rochester 2gc), fuel filter, points and timing.

Engine starts easilly and runs fairly smooth for a few minutes then loses RPM's and dies and/or loses power. Restarting is sometimes difficult, but seems to work best with throttle set at idle.

To me it seems the issue is related to the warmup -
* Could it be the choke? is there a trusty way to set the Choke? This carb seems to use an air/thermal choke, which I'm unfamiar with.

Set choke on a cold engine. Lightly set the choke closed.

* Might there still be water getting to the gas? Would it be worth putting a fuel/water seperator filter in?

Absolutley put one in this is one of the best things you can do for a boat.

* Could it be the coil? the one on it came with the boat.

Could be but stay with the fuel first. Remember this KISS "Keep it simple stupid" Don't take offense. Stick with troubleshooting the fuel system first. I sounds like a fuel delivery problem.

The big boss (wife) is getting tired of me throwing money at it and I need to be a bit more selective on what I apply funds to.

The boat is otherwise in great shape and is the best riding/handling in this size class I've been in, it'd be a waste for me to let 'er go.

Help!

Try a couple things. Run with your gas cap off and see if this helps, if it does it my be your fuel vent hose is plugged. Since it sat out uncovered it may be clouged. Also check your antisyphon valve it may be faulty. Also make sure that all the plug wires are on correctly since you changed plugs. As far as your choke, take off the flame arrester. It should be closed when cold and graudually open when it warms up. I hope this helps a little.

 

[Cromagnon35]

Re: '83 OMC 2.5L Stalling/Idel issues

Thanks for the info.

Been running it with the flame arrestor off for the most part. (covers off the engine, very remote chance of backfire causing *BOOM*) choke 'seems' to be operating OK, though a buddy has been fiddling with it.

I'll check out the vent idea - it may well be a problem there, and would fit the symptoms scarily well. ;-)

Thanks! I'm planning on trying to take it back out on labor day, so we'll see. I'll be throwing in some new plugs as well as the olds ones got a bit fouled from the carb being adjusted waaaay rich.

 

[wire2]

Re: '83 OMC 2.5L Stalling/Idel issues

After it stalls from running a few minutes, does it turn over normal speed or slow?

What can happen is;
Water in the crankcase floats oil up, including from around crank bearings. If you just change the oil & filter, some water will remain between the bearings, heat up & score the bearings/crank. It may start ok cold, then as the scored bearing heats and expands, it tends to partially seize.

A safer way to recover from a flooded crankcase is;
drain the water/oil, remove the oil sender, insert a hose fitting and force clean motor oil in with a pump. That will displace the water from crank (and cam) bearings. Let the water settle to the bottom, change the oil.

 

[Cromagnon35]

Re: '83 OMC 2.5L Stalling/Idel issues

Looks like the venting was the key - took 'er out and she ran like a champ!

Thank you so much for the tip!

 

[Cromagnon35]

Re: '83 OMC 2.5L Stalling/Idel issues

After it stalls from running a few minutes, does it turn over normal speed or slow?

What can happen is;
Water in the crankcase floats oil up, including from around crank bearings. If you just change the oil & filter, some water will remain between the bearings, heat up & score the bearings/crank. It may start ok cold, then as the scored bearing heats and expands, it tends to partially seize.

A safer way to recover from a flooded crankcase is;
drain the water/oil, remove the oil sender, insert a hose fitting and force clean motor oil in with a pump. That will displace the water from crank (and cam) bearings. Let the water settle to the bottom, change the oil.

Thanks - good tip.

I had changed the oil 2x and after it's intermittent running (2 hours perhaps all together) an oil check shows it to be exactly as it should be. Slightly brown with no emulsification (chocolate milkshake for the benefit of those searching the topic) and at the proper levels.

Root cause turned out to be the tank wasn't venting properly. Made sense the more I thought of it too - explained why the inline fuel filter kept going dry, carb was trying to suck vacumn.