1986 merc 90 six cyl troubles....please help

[SaltyDawg69]

Re: 1986 merc 90 six cyl troubles....please help

Ok great repository of knowledge. I cleaned out my carbs (again per a friends suggestion) and just got back from the lake and still I have the same problem. I decided to check out the motor as soon as I got home. Now, like I said the motor runs fine at an idle, but soon as I gave it throttle in gear it would drop its rpm's from 4500 to about 3000. By the way thanks for the info Clams Canino, I am a new/second time boat owner if that makes any sense. Anyway, I decide to inspect the wiring a bit closer and I believe I may have found the problem. If you can, check these pics out.<br /><br /> http://www.buchhorn.net\motor\P1010307.JPG <br /> http://www.buchhorn.net\motor\P1010308.JPG <br /> http://www.buchhorn.net\motor\P1010309.JPG <br /><br />I believe I have found my problem. If you look really close you can see tha tthe yellow wire was shorting to the starter. The one question I have you you gentlemen.. and ladies, is does any one know what these wires go to and what they are for? If I had the manual that came whit the boat I would find that out my self, but i just figure that some kind soul would tell me rather than refering me to the manual. Thanks in advance for all your info! This is a great forum!

 

[dakk1]

Re: 1986 merc 90 six cyl troubles....please help

Saltydawg<br /><br />Looks like the two yellow wires go from your rectifier to the stator. Charges the battery.<br /><br />Dave..

 

[Clams Canino]

Re: 1986 merc 90 six cyl troubles....please help

Ya.. yellow may or may not be the problem. But a good place to start and needs fixing anyway. Both of these motors have an existing history - so that we're SURE they aren't overpropped - right???<br /><br />-W

 

[SaltyDawg69]

Re: 1986 merc 90 six cyl troubles....please help

The motor has not been overpropped, but I will be getting the original prop back on here soon. It is off getting repaired. The original one is a 13" x19" orginal Aluminum prop and the replacement/spare I bought is one of those Comprop 12.7"x19", but I will go back to the Aluminum one once the shop is done with it (previous owner put a 2" crack in it). The wires are completely corroded and Hopefully today I will replace them and test out the motor tomorrow.

 

[dugdamoose]

Re: 1986 merc 90 six cyl troubles....please help

hey i thought i would jump aboard and share in the misery. i started a post titled; mariner 115hp inline 6 timing?; . i have the same problem. wont get up and go but will troll along all day long.i raced a guy in a canoe and i almost beat him. i havent tried to disconnect the yellow wire but will try it today. divo may have stumbled on to something . maybe a quick check on stator condition perhaps! one other thing i found with my engine is after i have it running with the muffs i noticed that the lower unit leaks oil .looks like around the back side of the prop.is that a seal gone bad? would that have anything to do with the problem? i doubt it but just thought i would ask!

 

[divo]

Re: 1986 merc 90 six cyl troubles....please help

I am still running it with one of the yellow wires disconnected (waiting for some cash for the new stator). It runs perfectly and I just make sure the battery is fully charged before going out for the day. I have noticed though, that every now and then the tach goes nuts....reads 8000 when its at bout 3000...or simply doesn't work for a short time. I am hoping he stator lasts a little longer. the weather is so nice, i cant just let it sit. Am I doing the motor any harm by running it for a few weeks( about 5 or 6 outings) with a faulty stator? Thanks

 

[dugdamoose]

Re: 1986 merc 90 six cyl troubles....please help

divo, where are you getting the new stator from? i checked out boatfix.com they sell for 127.51 to 191.27 if you need raceing performance your stator is the same as my 115 mariner part # 174-5456 good luck.

 

[divo]

Re: 1986 merc 90 six cyl troubles....please help

Thanks for the info Moose,I really haven't figured out where to get the stator yet. I will check that place out. Prob start searching next week. Thanks

 

[dugdamoose]

Re: 1986 merc 90 six cyl troubles....please help

hey ! i did the same as divo and unhooked the yellow wire from the rectifier and gave her the throttle she wanted to go but for some reason couldnt so i had my son squeeze the fuel bulb on the fuel line and after a few good squeezes she took off like a bat! she moved along at 50. after one time around i told my son to stop squeezing and she still ran fine. once in a while it would bog down again and he would have to squeeze it again. she would take off once again. (However) after i re-attached the yellow wire and she wouldnt even try to go. (just stall out) so i'm figuring a new stator but i'm not too sure whats up with the fuel.any suggestions? thanks!

 

[kdisop0]

Re: 1986 merc 90 six cyl troubles....please help

Hi divo, I appear to be in the same boat as you and a few others. I have an 82 90hp merc doing the same thing as yours. After I read your post, I quickly disconnected the yellow wires from the diode, no luck same problem, however I did not try to prime the ball. Next test I guess. This problem is such a pain because you have to have the engine under load to test it.<br /> Checking Diodes. Most all digital mutli meters have a diode test scale. The simbol for a diode is an arrow pointing at a vertical bar. If you place the black lead of the meter on the bar end of the diode and the red on the other the reading on the meter should be very low. This tells you that it is conducting when it is forward bias. reverse the leads and the reading should be very high or infinity. This tells you the device is not leaky. In all cases the diode should be out ot the circut when testing.

 

[stant1man]

Re: 1986 merc 90 six cyl troubles....please help

I think we have lots of engines her with various issues. Dugdamoose has what sounds like a fuel pump problem.<br /><br />Divo - Listen to Clams Canino, he works on these exact engines for a living and will eventually lead you to your problem if you follow his insructions.... Starting with the stator..

 

[LMPalmer]

Re: 1986 merc 90 six cyl troubles....please help

Originally posted by divo:<br /> I just purchased a used boat. It's a 1986 16' runabout with a 1986 mercury 90 inline 6. the sn is...a149755. Both are in very good contition and appear to have been taken care of very well. I put boat in the water and it ran good for about 5 minutes (at low rpm...less than 3000). then back down on throttle and try to accelerate and it wont go past 2000. it just loads up...drops some rpm's and jumps back up to 2000....but never over. I take it home...with service manual, 3 carb kits, fuel pump kit and plugs. Do the carbs (looked clean), do the fuel pump ( looked ok), changed plugs. I take boat back out and now it wont go past 3000 rpm. (sometimes 2500). it idles perfectly. if i rev it up a little to about 4000) in nuetral it sounds perfect. do carbs agin....all new gas, replace all fuel lines, install inline fuel filter,.When put in the new gas ( super premium) it increased the max rpm to 3000-3100. it seems like it is loading up. tank vent is ok. spark on all cylinders (at least when on muffs) primer bulb on gas line stays firm. The engine looks brand new under the cowl and the original owner installed a mercury service meter which reads about 80 hours. I dont know what to try next? Could it be electrical? Any help or ideas would be appreciated. Thanks

 

[LMPalmer]

Re: 1986 merc 90 six cyl troubles....please help

Divo,<br />I just purchased a used 86 6 cyl 90hp merc also. What fuel to oil mixture are you useing for the engine? (50:1)<br /><br /><br />PJ in SC<br /><br />Please reply to LPalmer@ftc-i.net<br /><br />Thanke

 

[Clams Canino]

Re: 1986 merc 90 six cyl troubles....please help

I just ran into a 4 cylinder Merc with the same stator problem, except that it was the low speed winding that was affected by the yellow leads.<br /><br />-W

 

[kdisop0]

Re: 1986 merc 90 six cyl troubles....please help

Hey Divo. Heres an up, got sick of working on it, so I took it to a local company called Vans. Here what the work order read. Ck spark and compression Good. Timing not Advancing. Torsion Spring in throttle lever unhook. disassemble lube and lock sring back together. Also bleed tube hose from bottom of power head to top was broken. Replace bleed hose. Test run ok.<br /> Boy, does this thing fly, its on plane in less than 2 sec, top end over 50 (guessing) no speedo and did not have gps with me. A $174.12 well spend, If I had only brought it there two years ago, all the fishin I missed. Happy Now