1987 3.7 165HP Merc Ignition Question

[bwthor]

I searched through the forums a bit, but got lost in all of the posts.

Anyway, my boat is about 2 hours away at my brother's cabin, so I can't go an take a quick look at it. He has been having some power issues as it won't rev past about 4000 RPM's. He is somewhat mechanically inclined, and has replaced the fuel filter, verified the carb is opening fully, replaced the rotor, cap and plugs with no success.

I told him to try and use some emery cloth on the points, but that didn't help either. I asked him to try and adjust the timing just a degree or two each way to see if that will help, and what do you know it did. I don't know if the distributor had turned somehow or what, but I am leaning toward some sort of issue with the distributor or the automatic timing advancing on the distributor.

Finally to my question. What system does this engine have to adjust the timing? Is it vacuum advance, or mechanical weight advance? I will be heading there this weekend with a timing light and a dwell meter to tune it up. Can anybody tell me if I can get a set of points at an auto parts store at a cheaper cost than the boat dealer? And does anyone know what the dwell settings, point gap and timing specs are? Also, does anyone know at what RPM's the ignition advance should change?

I know that this a lot of questions, but I would really appreciate anyone's help.

Brandon

 

[ta400man]

Re: 1987 3.7 165HP Merc Ignition Question

The points should be set to .022" with a dwell of 28-34 degrees. I have the same motor and there is a tag on top of the valve cover that told me the specs i just listed. To the best of my knowledge the advance should be a weighted system.

I would interested in the cause to your problem.

Thanks,
Shawn

 

[Reel Poor]

Re: 1987 3.7 165HP Merc Ignition Question

NAPA should be able to supply you with the parts you need.

Be sure to set the dwell BEFORE you set the timming. Also check that the timming is advancing properly.

Check the fuel filter in the carb fuel inlet.

 

[bwthor]

Re: 1987 3.7 165HP Merc Ignition Question

Thanks for the replies so far. Being away from my boat, I can't get much info from it as to what I need. Do you know if the timing specs are on that tag as well? I'll be sure to post what I find out this weekend when I go down there.

As for the fuel filter, my brother has already replaced it. He also took the filter cup off the bottom of the fuel pump as well and checked that, but didn't replace the stone filter.

Brandon

 

[Reel Poor]

Re: 1987 3.7 165HP Merc Ignition Question

If the tag is there it should contain all the tune up specs, timming, dwell, plug type and gap, engine family , and more.

 

[DHPMARINE]

Re: 1987 3.7 165HP Merc Ignition Question

Merc stopped using that stone filter years ago,and replaced it with a paper one.Maybe they had a reason.I don't 'check' filters,by the time you get there .... just replace them.Sorta like don't check a waterpump impeller.When you get there ... replace it.... don't reassemble with the used part.

As for the points,don't scrimp on the cheap parts.Eventually you'll have so many substitute parts,they will gang up on you.Case in point (not a pun) marine points run constant full RPM (above 4000rpm)(that is a pun) .How often do you run an auto wide open for as long ?

When you do need somethings $$$ then substitute.We just replaced a ring gear on a 454 flywheel for about $90.Merc seemed to only offer the whole flywheel for $425 as I recall.

DHP

 

[bwthor]

Re: 1987 3.7 165HP Merc Ignition Question

As for the points,don't scrimp on the cheap parts.Eventually you'll have so many substitute parts,they will gang up on you.

Thanks for the advice, you do have a good point on the points!! I talked with my brother tonight, and he did replace the filter on the fuel pump as well.

I think that this weekend, I will put in a new set of points & condensor and time the engine properly. I still think that i need to look at the mechanical advance system to make sure it is operating. Does anyone know at what RPM's I should see the timing change and about how many degrees?

 

[bwthor]

Re: 1987 3.7 165HP Merc Ignition Question

One other question. Some people that I have talked to said that the fuel that we get in Minnesota contains ethanol. I would guess that it is only around the 10% range though. I really don't think that the fuel could be the problem, but what have others run into with ethanol blended fuels.

 

[bwthor]

Re: 1987 3.7 165HP Merc Ignition Question

Problem Solved!!!

It was rather stupid. The gasket between the exhaust manifold and the coolant resevoir was leaking, and I think that was causing it to push some coolant into the overflow tank. Anyway, on my engine, the coolant overflow is located down on the lower right side of the engine. The cap on the overflow had a pin hole in the center of it, and when it filled up, it shot coolant straight up and on to the coil. When the coil got wet, it misfired. I replaced the gasket, put a new coil wire on it and solved the problem. While I was there, I replaced the points with a Merc tune up kit, and timed the engine.

It was really a simple problem, but without being there to diagnose it, I had no idea. Thanks for the replys and suggestions.

 

[MrBill]

Re: 1987 3.7 165HP Merc Ignition Question

For about $90 you can convert that ignition system to an electronic one. I did mine a few years ago with a Pertronix II,,,and wish I had done it 10 years ago. What a difference, never worry about dwell and points again.