Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

[mobileinfo]

I have a 1990 115 hp inline 4 mercury ss#oc171885. While running it this year I was getting a little nose when trimming up while in gear. I decided to change lowerunit gear oil. Check manual I bought off of Iboat and no mention of what type to use, found at local parts store a heavy duty high performance 85w-140 lucas. After short run I noticed it not shifting right. I drained lowerunit and refilled with quicksilver marine gearoil from walmart. Now it will start and run (in gear) for about 1 min then loses rpms dies. It will start back up when put in gear it dies. I'm at a loss for what to do next (other than take to boat mechanic). Thanks

 

[Maxz695]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Use 90 weight valvoline gear oil. The motor dying probably has nothing to do with the LU. Carburetors plugs compression check wiring grounds and connections must all be checked

 

[emoney]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

What do you mean by "after short run I noticed it not shifting right"? When you drained the gear oil to refill it, did you notice if it had water in it? Is it engaging in gear? The easiest way to check is on the trailer, motor NOT running, shift into forward, prop should turn (search "click" on merc's and you get a better feel for this) same for reverse and in neutral, prop should spin freely. Check that and then report back. Any problem, best to eliminate things first. A motor that dies when put into gear could be a "bound" prop (for example, I got dock line wrapped around mine, I found out because she would die as soon as I tried to put it into gear). Or, it could be a fuel-related issue (bad fuel pump or fuel pump diaphragm) and could be as simple as a bad vent on your fuel tank (what type are you using; portable or permanent?).

How comfortable are you working on it? That's probably the real first question that needs answered.

 

[mobileinfo]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

What do you mean by "after short run I noticed it not shifting right"? When you drained the gear oil to refill it, did you notice if it had water in it? Is it engaging in gear? The easiest way to check is on the trailer, motor NOT running, shift into forward, prop should turn (search "click" on merc's and you get a better feel for this) same for reverse and in neutral, prop should spin freely. Check that and then report back. Any problem, best to eliminate things first. A motor that dies when put into gear could be a "bound" prop (for example, I got dock line wrapped around mine, I found out because she would die as soon as I tried to put it into gear). Or, it could be a fuel-related issue (bad fuel pump or fuel pump diaphragm) and could be as simple as a bad vent on your fuel tank (what type are you using; portable or permanent?).

How comfortable are you working on it? That's probably the real first question that needs answered.

Thanks for your replies, Short time means 5 minutes enough to get up to plane tach about 4 grand then rpms started falling off bring shifter back to center and try to take off again and it dyes. No water when replaced with proper weight. It is engaging, clicks when put in forword and reverse and prop is spun. Prop not bound up. (Guess that answered trashed gears question). New built in 12gal tank with vent. I have ran several times since new tank. After some more research I'm leaning towards fuel pump problem. I'm fairly comfortable working on it. I think it has a 2 by 2 fuel pump system, starts and idles on 2 cylinders and when power is called for the other two cylinders are fed fuel and kick in. Winterizing this weekend and will use the fall and winter seasons to collect parts and knowledge for spring repair. Needing knowledge on how to tell if it is the 2 by 2, one or two fuel pumps. I would like to replumb from primer bypassing quick connect (seems problematic) to fuel pump, replace fuel pump and all lines. It is a two stroke so there is a oil enrichment system in there some where.

 

[CharlieB]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

The 2 + 2 only has idle circuits in the top two carbs, the lower two do not draw enough fuel to fire until throttle is opened enough for the increased air flow to begin drawing more fuel. As the throttle is opening there is an accelerator pump plumbed to the bottom cyls to give an immediate squirt of fuel to aide those cyls to begin making power.

There is a single fuel pump and an oil inductor system in the fuel system to mix the oil at a varying ratio, less at idle and increasing with throttle.

Have your model and serial and search with pictures at Merc parts

http://www.mercruiserparts.com/mercruiser_parts.asp

You may still find a link to a service manual at

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

Once dialed in exactly as prescribed in the manual, these are very good fishing motors.

 

[mobileinfo]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Great Info CharlieB Thank You!! Will post results.

 

[mobileinfo]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Happy Spring all! Thought I would update my post. Last weekend I pulled the tarp off my boat and picked up where I left off last season. I started with four fresh spark plugs and some carb cleaner and she fired up. I noticed a fuel leak from a line that led from the fuel pump accelerator to the bottom two cycl, I replaced that line to find that the accelerator itself was pouring fuel aswell. After inspecting it (taking apart and looking at diaphram which was worn and had a tear in it) I ordered a new "repair kit" from The #1 web site for genuine Mercury Mercruiser engines, parts and propellers which should be in later this week. While I was at it I replaced the fuel line from the boat to the motor including a new primer bulb and removed the quick disconnect as it leaked and suck air while turning or trimmed up.

 

[mobileinfo]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Hello again, Still had an issue stalling when put in gear. Checked compression... from top down... top being 1 and bottom being 4.... 1 had 120 lbs per sq in.... 2 had 115 lbs per sq in.... 3 had 120 lbs per sq in..... 4 had 115 lbs per sq in... ;-) So the compression is ok.. check spark with $3 spark tester.... 1 and 2 had NO spark.... 3 and 4 deep blue spark..... checked coil packs at poles (+ -)with multimeter while key as being turned and got juice (somewhere between 12 and 15 volts dc) on coil packs 3 and 4. Not sure about juice on 1 and 2 because about that time I notice the hot wire on the starter solenoid was lose (movable) went to tighten it and snap broke the post right off of it. (part ordered). Removed coil packs 1 and 2 for testing.... resistance between poles (+ -) .3 to .4 ohms.... resistance between either pole and tower (middle of coil) where the plug wire would go is 944 omhs......... Thoughts or ideas would be helpful.... found chunk of magnet last year on powerhead and had boat guy pull flywheel.... he said was in good shape and had been replaced because original was orange this one is black. I would say the *&^% with it except I keep having these damn wet dreams.... dreams about boating ;-)

A note about my previous post be careful with carb cleaner (it removes the oil from the gas) I read some where. Don't push it through the engine..... fill bowl and then drain

 

[CharlieB]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Switch positions of the top 2 coils with the lower two and test for spark again. This will show if you have a problem with the coils, or elsewhere in the ignition.

Download and study the CDI Ignition Troubleshooting Guide (free)

CDI Electronics Practical Outboard Ignition Troubleshooting

Oder, or build, a DVA Adaptor to use with your volt/ohm meter so you can test the ignition components following the clear directions in the CDI Guide.

You may have a broken wire in a trigger, or it could be a bad Ignition switchbox.

Either way, remember, there is NO RETURN on ignition parts. You must test, and retest again to PROVE THE FAULT before ordering any parts.

 

[mobileinfo]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Charlie you post such great info!!!!!!! Page 81 and 82 if some one else needs this for this engine. May you have a great Monday.

 

[Texasmark]

Re: Used wrong gear oil gears trashed? 115 merc inline 4 1990 model

Oh, and put the correct oil in your LU. It's under the Quicksilver badge and is either high performance or premium high performance....names are close...been awhile since I looked at a container. On the back of the plastic container they tell you what it is for; i.e. high performance or normal duty. Personally, if you didn't leave something out of your post, I doubt that a short run with the wrong oil trashed your LU. The problem would be long term and would include possible lack of resistance to water contamination. That is why the recommended oil is important. It's especially designed for marine applications where water penetration happens more often than desired and it adheres to the metal to provide a protective film.....special additives.

Mark