early 80's Mercury 80 outboard

[reese]

I have been experiencing the following symptoms with my motor:<br />- occasionally it feels like it only firing on 2 or 3 of the 4 cylinders<br />- motor starts fine, we tour around the lake for 20 minutes or so, stop the boat, someone gets ready to waterski, boat starts/idles fine, but when I go to hammer it to pull the skier out the motor dies (if I pull back at this point and then give it some gas it will pull the skier out fine).<br /><br />My mechanic is saying that the problem is caused by the switchbox, stator and trigger and that I need to replace all three. Replacing only the switchbox may cause the other two to overload and damage the new switchbox.<br /><br />2 questions:<br />1) how is the second symptom (motor dies when skiing) related to an electrical problem. It sounds like a carburetor problem to me<br /><br />2) Is it true that I need to replace all three parts<br /><br />Thanks for your help.

 

[corm]

Re: early 80's Mercury 80 outboard

Hi Reese,<br /><br />I would enrichen the idle jet 1/8th to 1/4 turn on both carbs. Another thing that happens on the motors is that when you shut off the motor it heats up. This will cause the fuel to boil out of the carbs. Before starting squeeze the primer bulb to fill the carbs to see if that is happening. A lot of the time a good fuel pump will catch up and self correct this problem. When was the last time you changed the water pump, it could be getting weak. They run about 9lbs of pressure at 4500-5300 RPMs on that motor.<br />A bad batch of gas will also cause the problem you have.<br /><br />As far as the Ing Sys,in a worst case situation you may have to do all 3,BUT I would not do it on my own boat. I don't have the price list at home, but it's $600+ for every thing if I remember correct today.

<br />Try the other things 1st<br /><br />------------------<br />...have fun...corm<br /><br />cubic inches = power<br />power = speed<br />speed = FUN<br /><br />Email me if you need to.

 

[reese]

Re: early 80's Mercury 80 outboard

I was just talking to my mechanic and he performed the following test to confirm that it's a switchbox/stator/trigger problem:<br />- Started the motor and started pulling the sparkplug wires of one by one. One or more of the wires didn't impact the performance of the motor.<br /><br />He is saying that since these 3 parts are original equipment (over 20 years old) you can't replace just one because the replacement parts have been upgraded.<br /><br />Does this sound right?<br />THanks.

 

[corm]

Re: early 80's Mercury 80 outboard

Well Reese,<br />All that test tells me is that one or more plugs are bad or maybe coils. To test the trigger you use a ohm meter. To test the stator and switch box you use a Direct Voltage Adaptor testor. You use can use both to test the coils. I'll look at the service bulitins and see whats up or maybe someone else knows.<br /><br />...have fun...corm

 

[halibut]

Re: early 80's Mercury 80 outboard

I have a 1979 70 HP, 3 cyl. that is having the samr trouble your engine is. It will run perfect for about 15-20 minutes at all speeds. After 15 minutes or so it will only make 1600-1800 RPM. I have taken it to a local Merc dealer 3 times so far. <br />1. First they thought it was the gas tank cap not venting properly, but problem remained with no cap on tank. (I also replaced the hose/primer bulb assy)<br />2. Next they checked the fuel pump and said it was OK and left original installed. Still problem remained. After this they decided it was either electrical or carbs needing rebuild. <br />3. Carb's were rebuilt with no change, so I guess I'm to the electrical problem? <br /><br />My engine will run fine at idle up to about 1/4-1/3 engine speed after that it boggs down and if I try to go WOT it acts like it will stall until I pull back slightly to about 1600-1800 rpm where it will run fine. At slow speeds all plugs appear to be firing OK, but I haven't been able to check while U/W with problem occuring. I'm not sure if the problem is showing up after the engine is at operating temperature or if it is a "under load" problem. <br />I was advised on another bulletin board to check the stator resistance and also fuel pump diaphram for holes. Any other suggestions would be appreciated. Thanks in advance!!

 

[ODDD1]

Re: early 80's Mercury 80 outboard

Reese, you got to find a new "mechanic"...this guy is using a shotgun approach to diagnostics that is gonna cost you more money than it should......find someone that can actually diagnose fuel/ignition problems....I have NEVER replaced all 3 pieces on an engine.....these triggers almost never fail....stator is a common prob but motor usually wont start when it fails [lose spark on all cyl] switch box can cause intermittent misfire on individual cylinders [as can coils]......now you got a better chance fixing it than HE did...LOL.