1990 3.0 l. manual and idle issues

[Sunsetrider]

New to I/O, I put my 1990 Thundercraft 1750 in the water a few weeks ago and it ran well. I know it has some water left in the tank from a long layover at the yard, but a new water separator filter was installed and I have a spare element on hand. Now the engine refuses to idle, just dies even at 1K rpm (per the dial).

1. I want to download my manual, but neither #10 nor #13 seem to cover my 3.0 Mercruiser #OC767925. Can't seem to find the correct manual.

2. I thought I would first try to replace the filter, thinking it may be saturated already, but of course I can't get it off, typical for me. I am using an offset-jaw type filter wrench. But that's one I'll have to solve myself.

3. I am toying with the idea of fiddling with the idle speed, but without the correct manual I fear screwing up the mixture by mistake. And if I have to do something with the distributor first, well that scares me off at this point . . .

All the while the battery is hooked up to a trickle charger (Battery Tender from the motorcycle) because the key was left in the wrong position overnight. *sigh* I'm off to a good start in my revived boating life!

Any random comment appreciated . . . other than "drop the hammer and step away from the boat!"

 

[Don S]

Re: 1990 3.0 l. manual and idle issues

1. #10 is the manual you want, your engine is actually an 89. Not uncommon for the engine to be a year older or newer than the boat. Year changes are different for each. Also, in manual #10, it should say 0C856450 And BELOW not 0C856450 And Above.
2. A steady pressure works best to remove them. When installing, oil the oring (NOT grease) and tighten by hand, no wrenches, and you don't have to get it crazy tight by hand either. Same with the oil filter.

As for your running issue, if you have water in the tank, you need to get it out before you replace the filter. If you have water in the carb, no amount of fiddling with the adjustment will help. It will have to be taken apart, cleaned, and reassembled with a carb kit.
You may also need a full tuneup, which does include points and condenser inside the distibutor, along with setting the dwell and timing.
Compression check wouldn't hurt either.
After that it will probably run fine. They do take maintenance.

 

[Sunsetrider]

Re: 1990 3.0 l. manual and idle issues

Thanks for the reply Don - and a big :facepalm: re the manual! d'oh!

The dealer (consignment) just finished cleaning the carbs and the tank last week. He installed the water separator filter because he wasn't able to get all the water out, and he advised me to change it in a week or so (now-ish).

I have a "stronger" pal coming by soon. I'll give him a shot at wrenching the dang filter off . . . and hope for the best on the idle issue, and hope I don't need a new battery as well. They don't like to go flat.

 

[Don S]

Re: 1990 3.0 l. manual and idle issues

The best thing to do if the tank is not full, is to jack the front of the boat up so the front of the fuel tank is higher than the back, water sinks to the bottom of gas, so all the gas will then be on the bottom of the tank and in the back.
Remove the fuel pickup tube from the tank.
Then with a cheap electric fuel pump, some cheap hose and a piece of 1/8 copper tubing hooked to the intake hose of the pump. Suck the water off the bottom of the tank and into a container so you can see when straight gas is coming out of the tank.
Use some pipe thread sealer (NOT Teflon Tape) and put the fitting back in the tank.

Sometimes it's easier to pull the whole fuel filter assembly and stick it in a vise where you can get some leverage on it.

 

[Leaddog]

Re: 1990 3.0 l. manual and idle issues

Just a note, I had the same issue with water and trash in the tank. Thought I got it all out, took a trip, and 1 hr 45 minutes into the trip the water separator was clogged. Doesnt take as much as you might think to drop the fuel pressure too low to run properly, or at all. Keep a spare filter on board and a filter wrench.

 

[Sunsetrider]

Re: 1990 3.0 l. manual and idle issues

Sometimes it's easier to pull the whole fuel filter assembly and stick it in a vise where you can get some leverage on it.

It's getting to that point. But will the gas spew out of the hose from the tank, or is there a way to cut the flow off? Or is the flow minimal enough to catch with rags???

I think I could drain the water with you suggested method right on the ramp road at the end of my street.

 

[Sunsetrider]

Re: 1990 3.0 l. manual and idle issues

. Keep a spare filter on board and a filter wrench.

Haha - I've already got that one figured out! But your comment makes me suspect my problem (idle only, everything else runs dandy) is unrelated to the filter . . . hopefully not carb related.