Mercury 150 xr4 oil injection question

[jhogue46140]

I have a question about the oil reservoir mounted to the tank. I noticed today while doing some maintenance on my motor the oil reservoir tank had an air gap at the top. I topped it off then bled the tank and lines. If I crack the cap open while the engine is running oil flows out the cap. So I know that oil is being pumped from the remote tank. However after I tighten the cap and shut the engine down after awhile the air gap is back. Is this normal? I would think it should stay topped off. Any suggestions on where to start troubleshooting? Any help would be appreciated. Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

I have a question about the oil reservoir mounted to the tank. I noticed today while doing some maintenance on my motor the oil reservoir tank had an air gap at the top. I topped it off then bled the tank and lines. If I crack the cap open while the engine is running oil flows out the cap. So I know that oil is being pumped from the remote tank. However after I tighten the cap and shut the engine down after awhile the air gap is back. Is this normal? I would think it should stay topped off. Any suggestions on where to start troubleshooting? Any help would be appreciated. Thanks Doug

It has to be leaking out somewhere. It should stay plumb full at all times.

hope it helps
John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

Thats what i thought but cant seem to find where. I think I will change out the lines and see if that makes a difference. I wasn't sure if a bad check valve could cause this. Thanks Doug.

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

I would think if it was leaking forward through a check valve, you'd have real hard and smokey starts because you'd have pure oil going to the carbs. It happens.

If it were leaking back, you would have to have a high vapor pressure pollutant (gas) in the oil to supply the vapor head you see in the tank.

There's a relief valve where the line from the boat tank T's with the short drain hose and the line to the engine tank. If it were leaking forward, instead of waiting for a 2 lb suction, you could get a burp of air in the engine tank with each cycle. You might also see that if there were extreme temperature variation on the engine tank.

There's your data. Sic-em.

hope it helps
John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

Hi John,
First thanks for the assistance. I have started troubleshooting. I am pretty sure there are not any leaks. If I bleed the tank there is no air gap while engine is running. It appears after I shut the engine off. After a few minutes air gap appears. I did notice as I was pumping the fuel bulb that I saw air bubbles going up the oil supply line. The oil line coming from oil pump to fuel line. They meet at a t valve. Could this be the problem?

Also I was wondering if the in line fuel filter,the small one on the side of the engine, should be full of gas. It is only about a quarter to half full when engine is running or stopped. Thanks for your assistance. Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

Put a clear piece of tubing (hardware store vinyl is fine) between the bayonet fitting and the fuel-oil T fitting. Watch it while it's running. There should be no air at all there. I suspect you have an air leak in your fuel system. That might be where the burp of air is coming from.

The lines on my engine are tight and clear all the time.

A fuel filter will normally trap a bubble, but with the way that one is oriented, it shouldn't be much. I ditched mine and put in a Racor fuel/water seperator. I was having WOT fuel delivery problems and just didn't want to burn down a powerhead messing with that mickey mouse merc filter.

hope it helps
John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

I think we might be getting close. There is an air bubble in the line from oil pump to the t fitting when engine is running. I have been looking at the water separator fuel filters. I will take a look at the one you mentioned. If I get one of these I can get rid of the little one? Where should I start looking for the fuel system leak?
I haven't had much of an opportunity to open her up. Most of the lakes I am at are idle speed only. I did get to open her up about a month ago. She ran really good. She does run a little rough when idling unless I keep my foot on the hotfoot. I figured the idle might need adjusted. Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

Do what I said with the clear line. A small leak anywhere before the fuel pump will suck in air. It could be anything from a leak in the pickup tube to the clamps on the oil mixer. A common place is the bayonet connetor.

Link n sync is critical on that motor for a good idle.

hope it helps
John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

I thought I had. Is the bayonet connector on the oil pump? Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

I thought I had. Is the bayonet connector on the oil pump? Thanks Doug

That's the quick connect between the hose and the engine.

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

It has been a long day and I must be denser than normal. Are you saying the bayonet is the quick connect between the hose and engine. Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

It has been a long day and I must be denser than normal. Are you saying the bayonet is the quick connect between the hose and engine. Thanks Doug

That's what I said. Mine was a perfectly normal plastic aftermarket replacement put on by the "Mercury" mechanic in Perham, MN. Only problem is it wouldn't flow enough fuel to run the engine at WOT.

hope it helps
John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

I haven't checked the bayonet yet but may have found the problem.THe line from the oil pump to the fuel line had gas in it instead of oil. I noticed as I pumped the primer that it filled up with gas. I am going to swap out fitting and then check the bayonet. Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

I haven't checked the bayonet yet but may have found the problem.THe line from the oil pump to the fuel line had gas in it instead of oil. I noticed as I pumped the primer that it filled up with gas. I am going to swap out fitting and then check the bayonet. Thanks Doug

I think that oil/gas T fitting is supposed to be a check valve. Not only will you pump a little air into the oil system, but you may also be running really lean on oil at startup.

I don't think the oil pump should be loose enough to let fluid force through it easily, especially backward. maybe it's over the hill. Never heard of it, but it's possible.

John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

Hi John,
Thanks for all of your help. I just got back to troubleshooting this. I checked the bayonet like you said and all looked good. I pulled the check valve and could easily blow back into it. I have replaced it and put a new fuel filter in and the problem is solved. I am no longer getting air into the oil line and tank. The fuel filter also stays full of fuel. Actually the throttle seems more responsive now too. I didn't realize it was lagging before but now is better than before. Thanks again for your help. I am going to go ahead and replace the fuel primer bulb and assembly. I noticed the line on the assembly is starting to crack and is stiff. I am also going to install a fuel/water seperator as suggested. Thanks again Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

Hi John,
Thanks for all of your help. I just got back to troubleshooting this. I checked the bayonet like you said and all looked good. I pulled the check valve and could easily blow back into it. I have replaced it and put a new fuel filter in and the problem is solved. I am no longer getting air into the oil line and tank. The fuel filter also stays full of fuel. Actually the throttle seems more responsive now too. I didn't realize it was lagging before but now is better than before. Thanks again for your help. I am going to go ahead and replace the fuel primer bulb and assembly. I noticed the line on the assembly is starting to crack and is stiff. I am also going to install a fuel/water seperator as suggested. Thanks again Doug

Just be sure you use a mercury primer bulb and line. Attwood just doesn't flow enough fuel for that gas hog.

Been there, done that.

BTW here's how that engine 'posed to run.

John

 

[jhogue46140]

Re: Mercury 150 xr4 oil injection question

Is moeller a good choice. I ordered a replacement one from cabelas with a gift card I had. Thanks Doug

 

[j_martin]

Re: Mercury 150 xr4 oil injection question

Don't know. This I do know. If you starve that engine, you'll make a boat anchor out of it in no time at all.

I put a fuel pressure guage on mine and shot the bugs out of the fuel system till I was perfectly confident. My trusted mechanic is the one that told me my aftermarket fuel hose might be contributing to the trouble, and pressure gauge tests verified his statement.

I also ditched the stupid little fuel filter in that engine, put in oversized plumbing to a Racor 60 gph fuel/water seperator, detail cleaned my tank and pickup screen, rebuilt the fuel pump, and replaced all the fuel hoses on the engine. Lastly I ditched the aftermarket (attwood) fuel connectors that the idiot "mechanic" in Perham had installed. Each item I did improved the fuel pressure at WOT. Now it's right at 5 lbs. (2 will run it)

hope it helps
John