1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

[kjspylite]

1989 Mariner 75 HP 3 cylinder
serial # 0C167888
compression within 7 PSI on all 3

Motor starts great and idles fine. Both in the water and on the muffs.

My motor is bogging under load. It has no acceleartion....zero. Just barely above idle speed. Sounds like its missing. I think I'm dropping one or two cylinders. I've made a DVA adapter and checked parts according to CDI's website. Tested while on the muffs, everything seemed fine. I did a spark test and all three jumped a 7/16" gap. I have a hard time gauging how strong the spark looks because this is my first boat. I can say it was not yellow, but a whiteish blue spark. When I was on the water, I pulled the plug on each cylinder, one at a time, to see what affect it would have. Pulling #1 had no change. The motor ran exactly the same. Pulling #2 the motor ran very roughly, very noticible difference. Pulling #3, I had a hard time telling if it made a difference. Sounds like I'm looking spark on at least #1, maybe #3 also. Very confusing since my DVA tests looked good. Its possible my tests were inaccurate because I am a novice, however, I did my best to follow the CDI instructions as well as the factory manual. I've looked all through the fuel system and do not believe it to be a problem: cleaned carbs with new gaskets and properly adjusted floats, needle seats looked good, new fuel lines, new fuel pump, checked for air bubbles with clear line, tried portable tank, new fuel fittings, have tried numerous idle mixture settings with no change, pumped the primer bulb or hit enricher with no change. All this leads me to belive its a spark issue since my compression is OK. Does this sound right to you guys?

I pulled the flywheel and this is what I found:



the insulation on one of the trigger wires is cracking and the casing has some cracks in it. The flywheel looked to be rubbing the stator a little. The magnets in the flywheel look good.

Lastly, I found I have a 16 amp stator, but I do not have a regulator, just a rectifier. Stator model number was Mercury part # 398-9873A24.

I have pulled plugs immediatley after shutting down on the water and found no signs of water intrusion. Nothing was steam cleaned and no water on the plugs.

Again, my DVA tests seemed good and they all three jumped the 7/16" gap, but I am still convinced I am dropping cylinder(s) and this is an ignition problem. Can anyone make any sense of this? Thanks for your help.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I finally found time to pull everything off and check it all out. This is what found:

View attachment 107745View attachment 107746

one wire on the trigger has completely corroded through where it just exits the base. it was broken further down as well but hangin on by three strands (a moot point). I'm assuming this is the cause of my bogging issue. I'm still concerned about the stator. Its has a lot of rub marks and it is a 16 amp stator. I do not have a votage regulator, just a rectifier. Anyone have any thoughts on this?

Nik

 

[Maxz695]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

did you check the wires from the stator as well it is notorious for corroding right where it exits the stator due to rubbing right against the block there I taped mine up real good to act as insulation against the block. When was the last time you changed the plugs? My Exhaust bafle plate was leaking into the exhaust side of the cylinder making it misfire. If the plate corrodes enough it will dump water into the cylinder like no tomarrow and the result will be as you state and if not fixed it will reek havoke on the internal parts of the engine as well as block out the spark plugs. A sure way to test this would mean possibly destroying the impeller. Run it without water and if it runs fine then there is water intrusion and needs to be taken down for inspection.

 

[RaScLeS]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

hey if you like the motor (they burn gas heavy) then get a brand new trigger stator and cd pack (if money allows) and just keep the old **** on the side. its old and worn out. clean the carbs do a lync n sync clean the fuel pump the motor will be in great shape. make sure the compression is very good before you drop this money

the post above mine is pretty frightening lol ill know how to test it atleast if that ever happens!

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I can't see my attachments in my 2nd post. Not sure if others can but I thought I'd post the pics so others can see for future reference.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

did you check the wires from the stator as well it is notorious for corroding right where it exits the stator due to rubbing right against the block there I taped mine up real good to act as insulation against the block. When was the last time you changed the plugs? My Exhaust bafle plate was leaking into the exhaust side of the cylinder making it misfire. If the plate corrodes enough it will dump water into the cylinder like no tomarrow and the result will be as you state and if not fixed it will reek havoke on the internal parts of the engine as well as block out the spark plugs. A sure way to test this would mean possibly destroying the impeller. Run it without water and if it runs fine then there is water intrusion and needs to be taken down for inspection.

the wires coming from the stator looked good where it exited the coils. I'm still concerned about the rubbing and the fact its a 16 amp when I think it should have been a 9 amp. The plastic around the posts on the rectifier were melted a little and I think it has something to do with the wrong sized stator. I went ahead and ordered a new trigger, stator, switchbox, and rectifier from CDI. We'll see how it runs with all the new ignition components on the water. I guess If runs poorly, I'll have to consider that I might have a water intrusion issue.

Here is a larger, more clear picture of the stator and the rubbing I am speaking of. This is not normal, is it?

 

[RaScLeS]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

that would be very sad after all those parts its got a water leak, while you wait prep the motor clean carbs ready to go. what is the compression?s

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I don't think I have a water leak because the pistons and plugs never look like they have been steam cleaned. I guess we'll see when I get it back on the water. Compression is good. I have a cheap harbor freight tester so I'm not sure if the actual reading is right but I do know they are all within 10% of each other. I was getting readings around 95 psi.

 

[RaScLeS]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

95psi? my 79' is pumping close to 130

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

my understanding of compression is that, while the higher the #s the better, it is significantly more important to have even compression. My factory manual does not give a PSI to be above, only each cylinder to be within 15 PSI of each other. Like I said above, I have a cheap tester, so my actual compression #s may be higher with a different gauge.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I have resolved my bogging issue and wanted to provide closure to this thread. I replaced the trigger, stator, switchbox, and rectifier with new CDI parts. I probably could have gotten by with just a new trigger, but figured for a couple hundred $ I could replace all these parts. The trigger was definitely shot and the sure cause of the bogging as you can see in the pictures above. I was unsure of the stator, it Ohmed out OK, but I didn't like that there were rub marks and I think I needed a 9 amp stator, not a 16 amp one. Also the rectifier had some melted plastic at the posts, probably due to the 16 amp stator with no voltage regulator. As for the switchbox, I figured, what the heck, i'm replacing everything else.

Took it out to the Pamunkey River east of Richmond, VA. Ran like a top. It was great from start to finish. Took a video to show off my proud work... http://www.youtube.com/watch?v=r5eDNsS4pi8

Thanks to everyone who offered help, not just in this thread, but all my threads asking for advice. I learned a lot by people responding to my questions but learned WAY MORE by just reading through all the different threads on this site (and reading my factory manual). Its become a daily ritual, checking the iBoats forums...

 

[moark]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

Sorry, was not intending to hijack your thead, I thought you were done.
Great thread though. Nearly the same problem as me. learned some things.

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

After all the things you have looked at, and if you still think it is ignition related, I would pull the flywheel so you can inspect the components. As you can see above, my trigger was dead. I was still able to start the boat and even get all three cylinders to jump a 7/16" gap, but in the water it bogged. It was very obvious, once I pulled the flywheel, the trigger was the root of my problems. I built a DVA tester, but I am not 100% confident in it. It seemd to give good readings sometimes and other times is was screwy. If you have confidence in you DVA tester, I would test, test, and test again. Try to get some consistent numbers to diagnose the problem part.

 

[moark]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

same

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I had a hard time identifying exactly what was causing my bogging. If you go to the youtube video I posted above, I have another video from a few weeks ago that shows my bogging problem. It sounds pretty obvious in the video that it is not running on all cylinders. While I didn't know exactly what was wrong, I was very confident it was a ignition problem. It wasn't until I pulled the flywheel that I found the faulty trigger. Hopefully what every is causing your problem can be as easily identified as mine was. Good luck and looking forward to your update. I would keep reading this site and your factory manual. My wife was getting mad at me cause I had my head buried in that manual every night!

 

[moark]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

same

 

[moark]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

same

 

[RaScLeS]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

AHAH another one working .....and what a hole shot you hammered it!!! what are the idle af screws set at? sounds nice how many rpm? pitch on prop ?

 

[kjspylite]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

My tach isn't working so i'm not sure of my RPMs. In fact, NONE of my gauges work, except for battery voltage. I did use a GPS and got a top speed of 37 MPH after trimming it up some. I have all of my idle screws set to 1.5 turns out.

Since you asked about RPMs...... I timed the motor just as the factory manual says to. 2 degrees BTDC at idle and 28 degrees (at cranking speed) BTDC. On the muffs it idles kinda high but slowed down in the water. However, I know it will idle even lower if I pull my trigger back by hand. Doing so will advance the timing to 0 degrees or even slightly ATDC. Is it worth it to idle that low and have my timing differ from what the manual says? Or should I just keep it where it is?

 

[Texasmark]

Re: 1989 Mariner 75 HP 3 Cyl - bogging no acceleration believe its a spark issue

I don't think I have a water leak because the pistons and plugs never look like they have been steam cleaned. I guess we'll see when I get it back on the water. Compression is good. I have a cheap harbor freight tester so I'm not sure if the actual reading is right but I do know they are all within 10% of each other. I was getting readings around 95 psi.

My Merc manual for the 90 hp is 150-165 factory fresh. "If you experience readings below 120 expect to have some problems." Then went on to mention the 10% was most important on balance since a lot of things affect compression. Squirt some 2 cycle oil in the cylinders and run the test again. If 20% roughly increase I'd say no biggie. If compression jumps up there, change the rings.

Mark