GM 4.3 High Idle/Timing Help

1989 Cadorette Holiday 200. GM 4.3 Vortec motor - ran great, very reliable. Water left in block over winter (drain holes plugged) whichi cracked block and heads.

Replaced with another GM 4.3 Vortec motor. Swapped over the intake, carb (4 bbl Q Jet), distributor, alternator, starter, flywheel, etc. Set base timing. Distributor is a non-HEI and has no vacuum advance. It has a separate coil beside it.

Took a while, but fired up. When it was running, it would idle at 2000 RPM. I know to check the timing, engine has to be warm. Question is, is it okay to run it at 2k until it gets warm to check timing with a timing gun/light? Or should I solve this high idle issue asap? Is it a timing thing?

Any help would be appreciated!

fix the idle condition first
you have a incorrect throttle adjustment or you have a base gasket leak or a intake manifold leak

I'm getting a new base gasket for the carb. I'm also going to disconnect the throttle linkage from the carb to eliminate that possibility (although I checked and the throttle linkage and there was no binding.

Intake gaskets were just re-done, but I'll spray some WD-40 or carb cleaner to see if it picks up RPM around those gaskets.

Someone has told me that 2000 RPM is about right for a cold start - is that true? Or should I back off the fast idle adjustment?

you disconnect the linkage when adjusting the idle screw, once you have the idle set you adjust the throttle to match.

Yeah, that's taken care of.

Does 2000 RPM sound too high for initial startup RPM?

Does 2000 RPM sound too high for initial startup RPM? Marine engines dont use a fast idle cam ????????
YES
If you have the throttle cable dis-connected and you cant get the idle down you have a carb issue or a leak issue

This isnt a stock marine engine. It's a replacement 4.3 out of a Chevy blazer/S10.

I thought when startup happens, the high idle is normal and then you can give it gas to kick it down to regular idle when warmed up?

Well I got it to run. I got the idle down.

Next question: There are 2 wires that come out of the distributor that the previous owner put tags on to remind that they need to be connected when setting timing.

Does anyone know what the timing should be with the wires connected?

got a pic of the ign system? yours shows a TB IV that is point and shoot. If its running theres nothing to connect

those 2 wires are for the base timing mode and connect together, should also be a third wire that gets 12 volts to activate base timing

And I still say that motor was underwater at some point, dist shafts are never that rusty

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JohnRichard said:

This isnt a stock marine engine. It's a replacement 4.3 out of a Chevy blazer/S10.
I hope that you have good luck using an Automotive engine in a Marine application.

I thought when startup happens, the high idle is normal and then you can give it gas to kick it down to regular idle when warmed up?
A certain increase in RPM during warm up is OK..... but not OK if excessive!

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JohnRichard said:

Well I got it to run. I got the idle down.

Next question: There are 2 wires that come out of the distributor that the previous owner put tags on to remind that they need to be connected when setting timing.

Does anyone know what the timing should be with the wires connected?

You have an EST ignition system. EST = electronic spark timing.
There is NO mechanical advancing system within the ignition distributor.
The distributor housing is adjusted as to give the system full advance.
Via the controller unit, this advance is delayed as per engine speed..... i.e., engine rpm.
The delay is then altered as per OEM specs as per RPM.

by jumping the two connections, it puts the controller into BASE mode.
Set BASE and then disconnect the jumper.

But...... if you are a savvy mechanic, you are not quite finished yet.
Use your strobe light and check the advance through the RPM range.
See your OEM work shop or OEM service manual for YOUR engine's ignition advance curve.

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Thanks for the replies.

This boat was bought off a family member and it's never been under water in its entire life. Where i live, the mix of humidity, temps and general moisture in the air has visible effects on all my toys. My exhausts on my bikes and snowmobiles develop surface rust annually.

The motor was swapped to a Vortec motor years ago. The shop that did it bypassed the ESA switch and this boat ran for years with no issues.

This past fall, I paid someone to do the winter prep while I was out of town (in the military) and although the water traps were opened, nothing was put in the drain holes to clear any blockages. Water was retained and cracked the block and intake.

I swapped another 4.3 from a Chevy/GMC in its place with all identical parts.

With help here (pictured above) I've been able to figure out things for timing and carb settings.

I got the boat running on muffs yesterday and it ran ok.

Today, I took it to a boat launch and put it in the water. Got the timing dialed in perfectly. RPM at idle set too. Both right to specs. Slightly before 10 minutes running, temp rose so I shut it off. It was getting late, so I brought it home.

Pulled the t stat housing and thermostat out. I'll re install housing tomorrow without the thermostat and see what it does. With the timing and idle set, it was purring like it has the past many years I've had it.

With the high temp, I noticed the 2 coolant lines that connect the housing to the exhaust manifolds were the pretty hot ones.

Regardless, I'll update with what happens tomorrow.

Ran without thermostat for 20 minutes and didn't overheat at all. Going to put in my new thermostat tomorrow and double check timing and idle then test drive it

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JohnRichard said:

Thanks for the replies.

The engine was swapped to a Vortec engine years ago. The shop that did it bypassed the ESA switch and this boat ran for years with no issues.
FYI.... the Dog Clutch stern drive should have a means of momentarily reducing dynamic prop thrust so that the Dog Clutch engagement teeth can be easily separated during a shift from gear back into neutral.

If the ESA is abandoned, then a SA or SI can be used.
(SA = shift assist...... SI = shift interrupt.... such as what Mercruiser incorporates with their Dog Clutch "A" drive)

This past fall, I paid someone to do the winter prep while I was out of town (in the military) and although the water traps were opened, nothing was put in the drain holes to clear any blockages. Water was retained and cracked the block and intake.
This is a good example of why we should use a shop who is licensed, bonded and insured so that we have protection in the event of improper winterizing.


Today, I took it to a boat launch and put it in the water. Got the timing dialed in perfectly. RPM at idle set too. Both right to specs. Slightly before 10 minutes running, temp rose so I shut it off. It was getting late, so I brought it home.

Pulled the t stat housing and thermostat out. I'll re install housing tomorrow without the thermostat and see what it does. With the timing and idle set, it was purring like it has the past many years I've had it.
Many initially look to the thermostat as being the culprit. The thermostat's involvement pertains to the coolant (seawater) that is leaving the cylinder block and cylinder heads.
Keep in mind that with a RWC engine, most all seawater is by-passing the engine demands and is going into and out the exhaust system.
I will suggest that you look further into the seawater path for restrictions. This means hoses, fittings, manifolds, elbows, seawater transfer ports, etc.


With the high temp, I noticed the 2 coolant lines that connect the housing to the exhaust manifolds were the pretty hot ones.
Yes..... see above comments.

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