MCM 3.7L Help?

[herricka]

New to this board... just opening with a question... I dealt with minor engine problems last summer and im hoping to get this resolved this year! ... on my 1986 170HP Mercruiser... whenever I went back to neutral... the idle would change. Sometimes 800rpm...sometimes 1200rpm...if I shutoff the engine and restarted it was fine. I have rebuilt the carb but, didnt solve this problem. A friend said, its probably the distributor advance springs sticking. ???<br />I will probably change to electronic conversion kit anyhow... Im assuming the springs are in the dist? Can i grease these? Opinions? Sugguestions?

 

[crazy charlie]

Re: MCM 3.7L Help?

I dont know if that will solve your problem,but take off the dist cap and rotor and see what you have.you will be looking at the springs at that point.Lube them and see what happens.When was the last time the cap and rotor were replaced?????Charlie

 

[herricka]

Re: MCM 3.7L Help?

Just replaced plugs/points/cap last summer. When you look inside the distributor, I cant see any springs... this isnt the shaft spring in see in the parts book is it? Or, perhaps under the plate...as in the old types?

 

[danthern]

Re: MCM 3.7L Help?

mechanical or vacuum advance?

 

[airman]

Re: MCM 3.7L Help?

Put a timing light on it. That will tell you if it is a sticking advance but that sounds like a good bet. I don't know of an electronic conversion available for the 470 that would affect timing but I'd be interested in hearing about it if one is available. Won't Float - I don't think there is a marine engine around with vacuum advance, they're strictly mechanical as far as I know.

 

[fireship1]

Re: MCM 3.7L Help?

Regal, Hello! Welcome to the group! If you are looking for your advance weights you have to look UNDER the breaker plate. It is under the metal plate that the points are mounted to. A good way to check if they are in fact sticking is to remove the cap and LIGHTLY twist the rotor. Depending on the rotation of your distributor it will turn slightly one way or the other. When you feel it start to move release your grip on it. The rotor should snap back with a click. If it stays turned the weights are sticking or the springs that tension the weights need to be replaced.You can try to clean them by removing the two screws that hold down the breaker plate assembly. Pull off the rotor and carefully lift off the plate. You will see the springs and weights after you remove the plate. My guess is they will be covered with rust and gunk. Clean them with carb cleaner or electrical cleaner. You do not have to take them out unless they are REALLY rusted and won't move. Keep a rag under the distributor as there is a vent there and the liquid will flow out as you are spraying. Either let the assembly dry or hurry it up with compressed air after cleaning. When dry soak the entire weight and spring assembly with WD 40. Put the rotor back on the shaft and twist it lightly back and forth. You should feel it twist and it should snap back like butter now. When you put the breaker plate back on you will have to readjust the point gap and the dwell as you will have disturbed them when you pulled the breaker plate. Be sure and check and reset the timing as that will have changed also due to messing with the points. If this does not help the advance then the weights might have lost their tension and probably need to be replaced. Chek with your Merc dealer and see if you can get em. If you really want to say goodbye to point, dwell and advance blues get an entire ignition upgrade from E basic power.com It is totally maintenance free and has no moving parts. Also when you reinstalled your carb did you set your mixture with a vacuum gage? Did you set your idle speed while IN GEAR and under load? Just trying to come up with some suggestions for you. Hope this helps! Keep posting and don't give up!

 

[herricka]

Re: MCM 3.7L Help?

Thanks fireship1, thats great info. As soon as the sub zero temp pass, I'll have to go out and check it! (upstate NY) That sounds easy enough.<br /><br />BTW, I set the mixture by disconnecting the throttle cable and setting it to run at 600rpm... read that someplace. Vaccum sounds like a better way but, where would I connect the vaccum guage?<br /><br />..and Ill probably go with with a electronic conv kit fir the distrib in the spring.... as long as I'm at it!..and I never give up!

 

[fireship1]

Re: MCM 3.7L Help?

Regal, If you look on the intake manifold where the carb mounts there should be a pipe plug somewhere in that area. That plug once removed will tap you right into the intake manifold vacuum. You need to remove that plug and screw a small brass hose barb with the same threads as that plug into the hole. Bring the plug to Home Depot or Lowes to match up the thread. Then after you have installed the barb just take a small piece of rubber hose push it on the barb and attach the gage to the hose. The gage has markings that will tell you the running condition of the engine. Its a good way to check and diagnose carb, valve, and other engine troubles. What you said about the idle adjustment is correct. But that is only part of the adjustment. Start by warming up the motor to operating temp, Set the idle speed to spec, disconnect the throttle cable, adjust the idle mixture in about three turns or until it lightly seats, back the mixture screw out about three turns or until it stops, start up your motor and let it idle for a few minutes, and then you would adjust your mixture screw in or out until you get the highest, steadiest vacuum reading on the gage. Next shift in to forward and then adjust the idle speed. I believe on your motor its between 500 and 600 rpm<br />Shut the motor off and reconnect the cable, shift back into forward and make sure that the throttle plates open fully in the carb when it full forward. (do this part with the engine off!)I understand that it is cold where you are. It's below zero here tonight here in New Jersey. I can only imagine how cold it is in upstate NY! Ever since I found this site I love to hang out here and try to help out fellow boaters. It's a great way to chase away the "it's winter and I can't use the boat" blues. Kinda makes me happy just to have a great bunch of people to talk about my favorite hobby with! Hope this info helps a bit. Good luck!

 

[kcole683]

Re: MCM 3.7L Help?

My 3.7 mercruiser does the same thing. I have found the adjustment of your throttle cable and the connections can make the throttle plates not close all the way each time. If you try all the things in the previous posts to no avail try a return spring in the linkage it might help your aggrevation.<br />I've noticed that the idle speed doesnt bother me much until the outdrive wont shift correctly from forward or reverse to neutral. This always shows up when docking,(not fun when it won't come out of forward when trying to reverse at the dock).<br /><br />I thought I had a shift cable adjustment promlem on my mercruiser until I figured the idle was to high.<br />Keep at it and you'll figure it out.

 

[MrBill]

Re: MCM 3.7L Help?

Regal...Doing a search on this forum for '3.7', '470' or '488' will yield many of the discussions about the Mercruiser inline 4 cyl 224cid engine and its peculiarities. <br /><br />I concur with spark-chaser, chances are real good that the throttle linkage may be causing your problem...it's happened on my 89 3.7L. Check that when brought to idle from gear that the linkage at the carb seats and is fully closed against the adjustment screw. Also check the port side linkage at the shift lever assembly that is connected to the shift and throttle cables.<br /><br />This site provides detailed part schematics that are very helpful. Go to your specific engine down to the serial number detail... http://www.mercruiserparts.com/mercruiser_parts.asp <br /><br />Regarding the switch to electronic ignition...you should know that some manufacturers and distributors do not recommend the electronic ignition for those in-line 4cyl engine with the stator and water-cooled voltage regulator charging systems. I was prepared to make the switch and was advised by the distributor to address the charging system first, then the electronic ig would probably operate well. As you'll find out searching for posts on this engine, there are several design quirks on these engines...charging system, closed cooling/heat exchanger, engines mounts, etc, etc. The 470/3.7L is probably the most hated, as well as the most loved small marine engine in use today. <br /><br />I am changing out the charging system for an alternator in the spring, but be careful on this one, too. If you have power steering, you'll need the alternator kit which mounts on the lower starboard engine side and has the two-belt pulley. This requires re-location of the coolant over flow tank and sufficient space in the engine compartment, not just any conversion kit can be used.

 

[kcole683]

Re: MCM 3.7L Help?

Regal_1, If you need another place for Mercury 3.7 information there is a forum at breezeworks.net that deals with the MCM 3.7 only.<br /><br />You'll fond info there for this motors quirks and problems.<br /><br />Good luck

 

[BRIAN03]

Re: MCM 3.7L Help?

Mr. Bill If you are going to put an alt. kit on your 224 cid. I have put many of those kits on and found a small secret. I pull the front pulley on the crank and bring it to a machine shop and have the new alu. pulley put concentric to the steel pulley and pinned. I have it pinned just a line up. Sometimes if you dont that pulley whips all over the place. Ive seen them shake the boat. I hate vibrations. I have it pinned for reference for alignment. I have it pinned so that the two pulleys can be assembled in the boat. I know there usally not alot of room in the bilge.

 

[MrBill]

Re: MCM 3.7L Help?

Brian03...I had been made aware of the pulley issue but your suggested fix is great. The kits designed for units with Pow Steering however have a two belt pulley...do you place inside the old single belt pulley and pin?

 

[BRIAN03]

Re: MCM 3.7L Help?

Yes I use the pins as a line up only till you torque up the bolts. If you look at the new pulley there is alot of play in the holes in relationship to the bolt size.