3.0L omc timing problems

[metal249]

just bought an 86' Seaswirl 17ft. bow-rider with the 3.0L OMC Cobra. The motor was rebuilt 2 yrs ago. The guy that had it before didn't do thing to the motor, assuming that the rebuilt motor was running correctly. I took it to the lake and found that I could only achieve 3400 rpm at wide open throttle(WOT) with the boat empty. It also took about one minute to plane, which it did at about 2800 rpm. When I got back from the lake, I looked in the original manual for the boat, and found it is supposed to operate at 4200-4600 rpm at WOT. Thinking it was the wrong prop, I looked at what was recommended for my boat(13 1/4X19p) and checked what was on the boat(13 1/4X17p). I checked the fuel filter and the points. I replaced the plugs(properly gapped), and checked the timing, only to find it set at about 30 degrees above TDC. I then took out the number 1 spark plug and checked TDC with a screwdriver and it was correct. I then set the timing to 4 degrees above TDC, which is the factory setting for the motor. After tuning the carb, I had it idleling at 550 rpm and it would start first crank every time. Took it back to the lake the next day, and now it wont even start until I advance the timing. Now I can only get 2900 rpm and the motor bogs down when I try to add more throttle than that. After running the boat around the lake, when I return the throttle to idle, in neutral, it revs up to 2000rpm, until I rev it really high in neutral, then it just dies. The motor will only achieve the 4200-4600 rpm it is supposed to when it is in neutral. On the advice of a friend, I checked the mechanical advance in the carb only to find it operates properly and freely. I cannot seem to find anyone who knows what is wrong other than it's probably a really bad engine miss or the timing chain was not installed properly. Any advice or knowledge on the subject would be VERY helpful. If any more info is required, just let me know.

 

[chiefalen]

Re: 3.0L omc timing problems

It has timing gears no chain. The dist. sticking? It wobbling, maybe worn out.

A little advise don't run it over 1200 on the muffs, in neutral.

 

[Don S]

Re: 3.0L omc timing problems

Reving your engine to 4600 rpm in neutral is a non test. It could do that on one cylinder. Second, you can't change props enough to gain 1000 rpm. So that's not your problem.

Here's a list of possible causes of low WOT.

Engine Won't Reach Operating RPM. Check

• Fuel condition. Type and Octane possibly old fuel
• Propeller pitch or diameter, damaged blades
• Restricted fuel pickup tube or anti siphon valve Fuel System Test
• Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
• Marine growth on hull and outdrive
• Wrong gear ratio in outdrive
• Restricted carburetor air intake (clogged flame arrestor)
• Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
• Poor cylinder compression Compression Test
• Carburetor defective, or wrong type.
• Fuel pump pressure and vacuum
• Boat overloaded, improperly loaded, or improperly trimmed.
• Engine Overheating
• Engine timing and ignition system operation
• Remote control cables and linkage for proper travel to open throttle plates fully.

 

[metal249]

Re: 3.0L omc timing problems

I 've seen this same table before.

1)I'm running 91 octane(w/ octane booster to insure high octane)
2)Prop pitch and diameter are correct, prop is slightly damaged, but if it is bent it is to small to notice.
3)The motor bogs when to much throttle is added, thus leading me to believe there is no shortage of fuel.
4)Crank oil changed after first trip with no difference in performance
5)Hull is clean
6)Original outdrive(stock gearing)
7)Intake is not clogged or obructed
8)I don't know how to check exhaust other than looking at it(appears fine)
9)Only 2yrs on a rebuild, doubt any compression problems
10)I had the carb apart and it looked very clean and functional.
11)all performance numbers given where with only myself onboard with constant trim adjustment to even achieve the rpms I did
12)motor runs a constant 175 degrees(new impeller)
13)throttle plate is open all the way when it is supposed to be

all this leads me right back to ignition and timing

 

[Don S]

Re: 3.0L omc timing problems

1)I'm running 91 octane(w/ octane booster to insure high octane)

You don't need that on a 3.0L engine

3)The motor bogs when to much throttle is added, thus leading me to believe there is no shortage of fuel.

But you didn't check, it could be sucking air.

8)I don't know how to check exhaust other than looking at it(appears fine)

This is what a broken exhaust shutter looks like when it blocks the exhaust passage in the drive.
Thanks for the picture Bondo

9)Only 2yrs on a rebuild, doubt any compression problems

Check it anyway, you could find your problem.

 

[bruceb58]

Re: 3.0L omc timing problems

First of all, I would replace the points and set the dwell with a dwell meter.

How did you verify that you were getting proper ignition advance? Did you check it with a timing light?

 

[metal249]

Re: 3.0L omc timing problems

Thanks Don S. I have I fuel pressure gauge I'm going to stick on it right now, then I'll check compression, but actually, I have the original OEM manual, and it requires at least 89 octane(timing at one degree below TDC). Timing setting for 91 octane is four above TDC. It says if you can find 96 octane, you can advance it a further 5 degrees, so with the timing so high I figured it would help.

 

[metal249]

Re: 3.0L omc timing problems

The wire from the coil to my points fell off(maybe the problem?) when I when taking it apart. I'm on my way to the store to get a Pertronix electronic ignition conversion and a new coil. Hopefully that will put an end to this. I've seen a lot of post about an ESM unit(I have no idea what this is) and that the Pertronix is bad for it unless you install some extra piece. Anyone know about this?

 

[Facetious]

Re: 3.0L omc timing problems

I have a 1987 4.3L OMC Cobra. I was having the same exact issues you are having. Mine would run great at idle and up to 2800 rpms, than would bog down and not rev any further. I had been working on this problem since the beginning of the season. I have renewed the coil, plugs, cap(twice), rotor, plug wires, points, condensor(twice), and rebuilt the carburetor. Set the dwell and timing to spec. Also checked the compression on each cylinder and they were excellent. I pretty much eliminated anything mechanical and had replaced just about everything electrical. I think I have pulled out half my hair. A buddy of mine who is a marine mechanic suggested I try the pertronix ignitor. I said what the heck, I've thrown enough money at her already, might as well try that. So I bought the Ignitor II and the matching coil (~150.00) and installed it in about 20 minutes. Re set the timing and fired it up. So far so good. Threw the ropes off and put her in reverse. It stalled. Apparently there is a mod with diodes and resistors i need to make and put on the ESA. going to do that this weekend. Looks simple. I'll link it at the end of my novel . Well, I increased the idle screw to compensate for the confused ESA and tried again. Idle was about 900 rpms, not good for the ole outdrive, but i had to test out the new ignition. She thumps lightly into gear and back out of the dock I go. I turn her around and shift into forward. Thumps lightly into gear and almost stalls. I head out of the Marina and putter through the no wake zone. Man the suspense!! lol. I finally get out of the No Wake zone and go for the gusto!! I was not prepared. The difference was unbelievable. It ran better than it ever has. And I get more rpms on the top than before. The response is awesome. Better hole shot too. I am most happy with the results. It kind of sucks that I couldn't pin point the problem, but at least it works good now. I'll post the results of the ESA mod after this weekend.

EDIT: Oh ya forgot the ESA Mod link =D
OMC Diode Fix

 

[Maclin]

Re: 3.0L omc timing problems

What is "Above TDC" is that BTDC? Before TDC? or are you going After TDC.

91 octane is not necessary, 87 is fine. Your manual or wherever you are getting the figures may be showing the "european" value of 91 which converts to 87 the way it is measured here in the states.

Maybe the distributor gear pin has sheared and the distributor is not rotating correctly and the timing is "moving around". Need to pull out the distributor and check that. It is #8 in this drawing which I believe is your configuration...:
http://www.dougrussell.com/partscatalog/volvo_omc/index.cfm?fuseaction=comp&group=136&GroupList=194,195,196,131,132,197,135,136,200,201,202,140,204,205,206,144,207

If distributor is ok then more thoughts....

• I do not know if it is the same type of points as others that have the separate tension spring, but if so maybe it was not installed correctly with the points. New points and dwell setting and retime is in order, double checking the spring action on the points, it has to be a lot of tension or you cannot rev.
• I wonder if the timing marks on the balancer are correct, maybe it has spun or is not the right one for the engine.

 

[metal249]

Re: 3.0L omc timing problems

I put on new coil, pertronix electronic igniton, and new plug wires. I checked TDC on the number one cylinder and the mark is correct. Runs much better. I set the timing and tuned it up (5 degress above TDC, idle at 550rpm), but when I give it a little rev, it stays at 2000rpm for a few seconds, before slowly dropping down to about 1000 rpm. I recheck the timing and it jumped up to 20 degrees above TDC. I also put a fuel pressure gauge on it. It reads 3.5 psi at 1000rpm and 3.5 to 4 psi at 2000rpm. Is my pump bad?

 

[chiefalen]

Re: 3.0L omc timing problems

My 2 cents:

1- Disconnect the esa and run it. Problem still there?

2- Fuel pump should be between 4-6 pounds. Check the fuel/water separator.

Check the anti-siphon valve. Check the fuel pickup. Check the fuel filter at the carb fitting. Check the fuel filter in the fuel pump.

Check the tank vent.

All good new fuel pump than.

Good luck!

 

[Maclin]

Re: 3.0L omc timing problems

but when I give it a little rev, it stays at 2000rpm for a few seconds, before slowly dropping down to about 1000 rpm. I recheck the timing and it jumped up to 20 degrees above TDC.

Why do you think the timing moves around? Did you check the distributor shaft gear pin?

The engine does not want to come down to idle because the timing is up in the trees and the idle is affected. The timing did not change until you revved it and put stress on the distributor mechanism. There could very well be a problem with the fuel pump also but it would not make the timing change like that.

 

[tomwhysy]

Re: 3.0L omc timing problems

I would simply check the rotor and advancing mechanism its sounds like its varying that 30 degres that it should normally advance , maybe a broken spring ?
Simple test with your light on raise rpm of your engine and watch timing mark move BTDC my light allows me to set advance right on it and observe at TDC
you should get maximim advancement about 32-35 BTDC at 2500 rpms .
I turbocharged few 4 bangers before and we were locking distributors to stop it from advancing and when first started being locked at 25 deg BTDC they idle very high. if the mark is allover the place than new distributor will fix the problem .
If it had sheared pin in it it wouldnt run at all becouse ignition would be just random. than check if rotor sits in its grove and its not allowed to turn .
My diagnostic is a broken advancment mechanism!!!

 

[VMAX]

Re: 3.0L omc timing problems

Is the problem a bad overstroke switch for the ESA?
I have 2 Cobra boats right now with inoperative overstroke switches.
They shift into gear fine, but under acceleration, The ESA can kick in and bog the engine if the overstroke switch doesn't work. They should have just named it the ESA lockout switch. By installing a Pertronix ignition, you have eliminated the ESA. The test would have been to simply unplug the switch connector
in the first place. I wouldn't be suprised if the problem returns once the ESA
mod is put in place. Let us know if the problem returns. ESA switches are easy to replace.

 

[metal249]

Re: 3.0L omc timing problems

Do all cobras have ESA's? I don't understand what an overstroke switch is.
Also, as I have said before, the mechanical advance is operating fine and the springs are intact.

 

[bruceb58]

Re: 3.0L omc timing problems

Most Cobras have the ESA. The only ones that don't are the ones starting 1n 1994. The overstroke switch's purpose is to disengage the ESA if the ESA cam is stuck in the extended position. It is not needed with newer ESAs because the newer ones just use A timer to only allow the ESA to work for a certain length of time.

The ESA has nothing to do with timing and I don't think it is your problem. Like a previous poster said, you can easily eliminate it as the cause by disconnecting it. Shifting will be a pain but it is a good test.

 

[metal249]

Re: 3.0L omc timing problems

Just did a vacuum test off the carb. 10 inches at 1000rpm and 15 inches at 2000rpm. I think that is about right. I also think that eliminates a misaligned timing chain as the problem. I also put a fuel pressure gauge on it. It reads 3.5 psi at 1000rpm and 3.5 to 4 psi at 2000rpm. That seems low to me.

 

[metal249]

Re: 3.0L omc timing problems

I just did a compression test.
1. 115psi
2. 105psi
3. 105psi
4. 105psi
I don't know what these numbers are supposed to be, but they are all pretty even.

 

[celstad]

Re: 3.0L omc timing problems

moved comment