470 Has Me Stumped

First off it is a 1984 Mercruiser 3.7 470. Engine serial # 6738510. I've only had it about three weeks and don't know much about marine engines, but I am learning as I go. I did buy Mercruiser manual # 3 and I am using that as my reference along with this very helpful forum. It has a tune up kit which includes points,condenser, plugs and wires, new dist.cap. The manual says timing should be set at 8 degrees but I read on these forums that there was a service bulletin that it should be set to 4 degrees. This initial timing is on the muffs. When i initially checked it the prior owner had it set to about 10 or 11 degrees. It was very hard cold starting and would not idle properly. I moved timing to about 6 degrees and same thing. Moved down to 4 degrees and it wont barely start and will not idle for more than a second. So I put it back to the original 10 degrees and at least it will idle, but cannot throttle up without it bogging out and dying instantly. So I figure I will move the timing further out than 10 and it seems to idle properly with some carb adjustments to idle screw and fuel air mixture screw but if you feather the throttle up it will gain rpm's and stay running. This seems to be the spot where it runs the best. If I had to guess where it is I would say the timing mark is out to at least 20 degrees as the marks only go 10.
We put it in the water and I went to take off and give it some throttle and it would stumble and the level out. More throttle it would stumble and level out and so on until I was cruising around at about 3800 rpms and still had more to go, but I didn't want to push my luck. Temp was running steady around 145, and oil pressure close to 80. 80 seems high but I don't know if guage is correct. Also oil level is above full on dipstick, I need to siphon some out. This was maybe a 5 minute quick cruise before I came back to the launch. It would die at low rpm going in and out of gear at low rpm trying to trailer it but start right up with turn of the key and no throttle. I guess has anyone ever heard of these marks for timing being that far off and it still running better than it does within spec? I have other issues also but I guess I need to quit being so long winded. Thanks for your suggestions

Re: 470 Has Me Stumped

OK it should run just fine at 4 degrees bdc. Did you check the dwell? Since it is a new to you 470 there are a couple of things that I recommend to anyone, and that is do a compression check and cooling system pressure check to make sure everything is OK. You can borrow the tools from autozone to do the tests. I would think the chances that the timing marks are wrong is about 0. You might check to make sure the plug wires are in the right firing order, and that when you are at TD compression (timing marks lined up) tat the rotor is pointing exactly at the #1 plug wire. I suspect that a carb rebuild may be in order. Good luck, and welcome to the "470 club" :facepalm:

Re: 470 Has Me Stumped

stonyloam said:

OK it should run just fine at 4 degrees bdc. Did you check the dwell? Since it is a new to you 470 there are a couple of things that I recommend to anyone, and that is do a compression check and cooling system pressure check to make sure everything is OK. You can borrow the tools from autozone to do the tests. I would think the chances that the timing marks are wrong is about 0. You might check to make sure the plug wires are in the right firing order, and that when you are at TD compression (timing marks lined up) tat the rotor is pointing exactly at the #1 plug wire. I suspect that a carb rebuild may be in order. Good luck, and welcome to the "470 club" :facepalm:

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I have done a compression test with the engine up at operating temp. Cylinder #1- 155, #2-155, #3-160, #4-155. I thought those were pretty good numbers but I may be wrong. I did set the points with a feeler gauge at .022. I have no dwell meter to check dwell and I know I need to do this.I will be picking one up soon. Plug wires have been triple checked and are correct. I am having a problem finding a carb kit for this carb. I believe it is a Mercarb because of the one mixture screw instead of the two on the Rochester. The PO told me it needed to be rebuilt but I do not know which kit to get. The numbers on the carb are as follows: 06080A-1. 3701 . Everyone I have talked to about a carb kit says I am missing a number. I have removed the paint underneath the fuel inlet on the carb and this is what is stamped into the carb. If I knew how to post pics I would take some of the carb and maybe someone could figure this out. It is so frustrating. By the way I opened the carb up and took it apart per the manual and it was about brand new inside. It had definitely been reIbuilt recently but I dont think correctly. It is missing the baffle and has no check ball or screen and retainer in the accelerater pump well.It also has the accelerater pump with the 90 degree bend at the top. Maybe it needs the straight shaft one? I don't even know if this is the correct carb for this motor.If the dwell was off would that make this engine run so poorly at 4 degrees timing versus the 20 or so it is at now? Thanks

Re: 470 Has Me Stumped

Did you try and re adjust the idle after lower the timing down? Here is a copy of that TSB.

Have you tried to adjust the idle mixture screw on the carb?

Re: 470 Has Me Stumped

i went threw the same problem on my 83 470 when i rebuilt i converted to electronic ignition that being said i adjusted the timing to 4degrees and it ran bad the so i went to 6 degrees and it ran great and still is, going all the way to 20 degrees does not sound good i think you need to go back to your distributer i'm not an expert on electronics but i suspect that's where your problem is sounds like your out a couple of notches . i highly recommend converting to electronic ignition.
what does your boat have voltage regulator or alternator?

Re: 470 Has Me Stumped

Scrambler99 said:

I have done a compression test with the engine up at operating temp. Cylinder #1- 155, #2-155, #3-160, #4-155. I thought those were pretty good numbers but I may be wrong.

It had definitely been reIbuilt recently but I dont think correctly. It is missing the baffle and has no check ball or screen and retainer in the accelerater pump well.It also has the accelerater pump with the 90 degree bend at the top. Maybe it needs the straight shaft one? I don't even know if this is the correct carb for this motor.If the dwell was off would that make this engine run so poorly at 4 degrees timing versus the 20 or so it is at now? Thanks

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Those numbers look good.

If you have the pump with the 90 degree, then you need the 804844002 kit, that does not use the screen and check ball, the two accelerator pumps are not interchangeable, the the "bent" one is larger and would not fit in the hole for the "straight" one. You have the 96551 pump #33 here: http://www.mercruiserparts.com/Show...r=50&bdesc=CARBURETOR(MERCARB)+(165-170-3.7L)

If the dwell were way off the points would not be closed long enough for the coil to build up a good charge and the spark would be weak.

You could remove the distributor plate and check that the centrifugal advance weights and springs are in good shape and move freely.

Re: 470 Has Me Stumped

Eric 3.7LX Alpha 1 said:

Did you try and re adjust the idle after lower the timing down? Here is a copy of that TSB.

Have you tried to adjust the idle mixture screw on the carb?

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Yes we tried to adjust the idle with the idle screw and also the idle mixture screw. Nothing seemed to work to make it idle like it should at 4 degrees.

Re: 470 Has Me Stumped

fmalott said:

i went threw the same problem on my 83 470 when i rebuilt i converted to electronic ignition that being said i adjusted the timing to 4degrees and it ran bad the so i went to 6 degrees and it ran great and still is, going all the way to 20 degrees does not sound good i think you need to go back to your distributer i'm not an expert on electronics but i suspect that's where your problem is sounds like your out a couple of notches . i highly recommend converting to electronic ignition.
what does your boat have voltage regulator or alternator?

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My boat still has voltage regulator

Re: 470 Has Me Stumped

stonyloam said:

Those numbers look good.

If you have the pump with the 90 degree, then you need the 804844002 kit, that does not use the screen and check ball, the two accelerator pumps are not interchangeable, the the "bent" one is larger and would not fit in the hole for the "straight" one. You have the 96551 pump #33 here: http://www.mercruiserparts.com/Show...r=50&bdesc=CARBURETOR(MERCARB)+(165-170-3.7L)

If the dwell were way off the points would not be closed long enough for the coil to build up a good charge and the spark would be weak.

You could remove the distributor plate and check that the centrifugal advance weights and springs are in good shape and move freely.

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I am going to go down to buy a multimeter that has dwell and tach on it today. I think this is a good place to start with double checking the point gap and set the dwell. It makes sense that the timing mark wouldn't line up at 4 or even 6 degrees and run correctly if the dwell wasn't set correctly. I will also get a carb kit for the "mystery" carb. If I can figure out the posting of pics I will take some and post them of the carb. The centrifugal advance weights and springs are in ok shape for a 28 year old boat. They moved freely but I added a few drops of Marvel Oil at pivot points just to be safe. Thanks Again

Re: 470 Has Me Stumped

You have the correct carb, it is the "newer" model Mercarb 3310-860071A2 with the single idle mixture screw and the larger accelerator pump. Looks like this http://www.mercruiserparts.com/showSpecialPicture.asp?pn=860071A2 right?

Re: 470 Has Me Stumped

Scrambler99 said:

My boat still has voltage regulator

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check to see what it's pushing out to battery

Re: 470 Has Me Stumped

I have been doing some research on this "mystery" carb. When I Google Mercarb 06080A-1 3701 it comes up with Accelerator Pump Rod for a 1993 4.3L V-6 carburetor. Seeing that my engine is a 3.7 L I am starting to think that the prior owner put the wrong carb on this engine. Maybe this is why when I get the timing in the vicinity of 4-6 degrees I can't get it to idle properly.I hope you guys can come up with a solution for this problem. It just doesn't make any sense to me unless it is the totally wrong carb. I was thinking it was a 1983 carb, off of the numbers on it, until last night it dawned on me that this is probably a 1993 carb for a 4.3 L V-6. This is all I can come up with so I need your help. If it is the wrong carb is it just a matter of re-jetting it or do I need to buy a whole new carb. I am determined to figure this situation out and I have faith that we can all come up with a solution. Thanks again!

Re: 470 Has Me Stumped

Thanks again Terry for straightening out my carb situation in my other thread. Now do you think I should pull distributed shaft and re-align it one tooth over so my timing marks are closer to spec. I guess I'm asking where would you start if you had my problem?

Re: 470 Has Me Stumped

You also have to adjust your idle when adjusting timing. The faster the idle the more advance you get with the centrifical weights. I would not pull the distributer unless you couldn't get it to run at all. Are you hooking the timing light pickup to number one plug wire?

Re: 470 Has Me Stumped

Scrambler99 said:

Thanks again Terry for straightening out my carb situation in my other thread. Now do you think I should pull distributed shaft and re-align it one tooth over so my timing marks are closer to spec. I guess I'm asking where would you start if you had my problem?

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Actually that will not make any difference, because the relationship between the timing mark on the rotor and the TDC mark on the cover is fixed by the timing chain around the crank and cam gears, and by jumping the distributor a tooth, all you are changing is the points timing that is set by the relationship between the distributor cam lobes, the points the rotor and cap. so in effect all you are doing is the same as turning the distributor. Well first off I would check to see that TDC is really TDC. Turn the crank until the rotor timing mark is exactly lined up with the TDC mark on the cover (compression stroke). Make a mark on the side of the distributor exactly at the center of the #1 Remove the cap and determine if the rotor is pointed exactly at the center of your mark. If it is lined up you have a good starting point. Next I would check the coil, Pull the center wire from the cap and lay it close to bare metal on the block, put a piece of insulating material between the points, turn on the key and with a piece of insulated wire briefly jumper the points, every time you remove the wire you should get a strong blue spark, if not your coil may be weak, check the connections. If OK put it back together,get it started and check the dwell, get that correct, and try to get it to run at 650 to 700 rpm. Recheck the timing and see if the idle adjust screw works. If not you may have a carb problem. Try to get it to run as smoothly as possible at as close to 4 degrees BDC. That is what I would do, but what do I know LOL?

Re: 470 Has Me Stumped

Yes it is hooked up to number one plug wire.

Re: 470 Has Me Stumped

stonyloam said:

Actually that will not make any difference, because the relationship between the timing mark on the rotor and the TDC mark on the cover is fixed by the timing chain around the crank and cam gears, and by jumping the distributor a tooth, all you are changing is the points timing that is set by the relationship between the distributor cam lobes, the points the rotor and cap. so in effect all you are doing is the same as turning the distributor. Well first off I would check to see that TDC is really TDC. Turn the crank until the rotor timing mark is exactly lined up with the TDC mark on the cover (compression stroke). Make a mark on the side of the distributor exactly at the center of the #1 Remove the cap and determine if the rotor is pointed exactly at the center of your mark. If it is lined up you have a good starting point. Next I would check the coil, Pull the center wire from the cap and lay it close to bare metal on the block, put a piece of insulating material between the points, turn on the key and with a piece of insulated wire briefly jumper the points, every time you remove the wire you should get a strong blue spark, if not your coil may be weak, check the connections. If OK put it back together,get it started and check the dwell, get that correct, and try to get it to run at 650 to 700 rpm. Recheck the timing and see if the idle adjust screw works. If not you may have a carb problem. Try to get it to run as smoothly as possible at as close to 4 degrees BDC. That is what I would do, but what do I know LOL?

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I will try your suggestions and keep you posted on the results. Thanks Again!

Re: 470 Has Me Stumped

I found TDC on compression stroke and marked distributor.I transfered that mark up to breaker plate. My mark is the black mark next to edge of red tape. The original alignment mark on breaker plate is edge of blue tape. (I put the tape in there so it was easier to see in photos.)I measure about 9/32" between the marks. I am learning so please bear with me. The rotor is not pointed exactly at the center of my mark so what should I do next? Remember this is a learning experience for me, but I sure am trying. I'm sure glad I picked this motor to start out on! At least I am part of the "470 Club!" LOL Thanks

Re: 470 Has Me Stumped

I assume it is relatively close to the #1 post on the cap? Put the cap back on and mark the exact center of the post(on the cap) below just like you did with the other mark.

Remove the cap so now you have a mark where the #1 post is at. That mark can't/won't move.... If you turn the engine so that the rotor is pointing dead on the new mark.... and look at the timing marks on the balancer.... that should be your timing at idle setting.

Re: 470 Has Me Stumped

My center of the number one post is approximately 1/8 inch away from the center of rotor mark at TDC. Is this within reason or should it be closer to rotor alignment mark? Remember my timing is still out at about 20 degrees.