2005 18hp Nissan 4 stroke blowing oil out of the intake

[msaunoras]

Alright, new issue I've run across. The engine starts and runs fine (and now it shuts off good too), yesterday I happened to notice a decent sized sheen on the water trailing behind me. Pull the engine cover off and the whole right side is soaked in oil. Check the oil level, it's good but it smells a lot like fuel. The oil only has a 5-6 hours on it. I happened to be in the area of my dealer so I stopped in. He pointed out the oil coming out of the intake(and on the inside of the engine cover) but didn't give me a direct reason of what could cause this.

Backstory is I put synthetic in it. I read both ways on here, some say don't use it others say it doesn't matter. I'll say for sure the synthetic made the problem ten times worse. I've always run merc (quicksilver) semi-syn and it's never leaked bad, I never actually paid attention to where it was coming from. So I drained the synthetic put the old brand oil back in and it's still blowing out.... not nearly as bad though, not enough to drip into the water.

My question is, what the heck is causing this? My oil isnt growing like you'd think it would if fuel was leaking into the crankcase, I check the level all the time and it's not an overfull condition. I don't idle the engine excessively or troll with it. It's pretty much part-wot throttle all the time.

Thanks

-Matt

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Something else is going on with this engine, I really hope it's not a compression problem. I had a passenger with me on the water tonight, only an extra 200lbs, and the damn boat wouldn't register over 16mph on the lake. It definitely had a lack of power.

I also noticed tonight that my primer bulb wouldn't harden up at all, not even a little when squeezed.... so I'll start there, hopefully I have a bad bulb or a air leak.

I also read that my oil level should be on the minimum line or it could blow oil. My level is right in the middle of the hash marks on my stick so maybe I'll check it again and drain a little out tomorrow.

 

[pvanv]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

You definitely need to run FC-W rated 10w-30 non-synthetic, and definitely want to be half way on the dipstick. Did you change the filter with the oil, or did you leave that cup of synthetic in the motor?

If the primer won't get firm, either one of 3 things is the issue: there is a leaky check valve at the bulb, air in the system, or a flooding carb float valve.

Wouldn't hurt to check compression, and do a leak-down test. Your dealer should be able to help you with the latter.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

No, admittedly I didn't rechange the filter so there still is some full syn in the engine. The oil level is right in the middle of the marks on the dipstick and it isn't growing. It isn't blowing oil out nearly as bad, right on average of what it always did and it doesn't smell like fuel anymore. I was just curious about what could cause that, obviously it's likely a sealing issue with the rings causing excessive crankcase pressure made worse by the thin nature of synthetic.

I found the primer bulb gets rock hard if I hold it in the vertical position but goes soft if I let it lay flat. I assume the internal check valve is bad and the bulb/hose needs replaced. How urgent is this? Could it cause any running concerns?

I want to check my lack of power concern again with just me in the boat, I'm not used to having a passenger, I will be able to tell for sure what it should be running like and what speed I should achieve with just me onboard.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

I'm hitting the same GPS confirmed top speed as before with just me in the boat, it ran great tonight. I wonder if the prop is the issue, I can only imagine the extra weight is pushing it out of effective range. I guess I really need a tach to know that.

 

[pvanv]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

If you do a complete oil change (with filter), you should reduce the "synthetic blues" some. There is a slight possibility that you have never really seated the rings, even after all these years... especially if you ran heavier oil, or synthetic... or did a lot of trolling, or ran in cold waters a lot. Run that motor HARD and HOT for a few hours to promote ring seating. There will always be some oil (fumes, droplets) coming out of the breather hose, which connects to the flame arrestor (breather, or air box) at the carb inlet, so that is normal.

If the bulb works well when vertical (but not horizontal), that is a definite clue that the inlet check valve in the bulb is not staying sealed. Gravity is assisting the check valve to seat when vertical. But, it's not too big a deal, as the fuel line is actually under suction when the motor is running. Ultimately you will want a new one.

The extra weight is likely what slowed your boat. A change in trim or jack height may help that. Every boat is unique, so you may want to experiment some to see if you can improve speed with higher loads.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Well Paul I figured out the other half of my problem. Lack of power with a passenger? Yep, the prop on my outboard is not original. I dinged up the original about 5 years ago and got a replacement. No idea that the replacement prop was a 10 pitch until today. I always assumed it was the oem 9 pitch that was installed.

I bought a stainless 9 pitch to swap over to and found it today. So no idea how a stainless 9 will react with just me in the boat, the aluminum 10 was perfect for just me but no good with passengers.

 

[pvanv]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Stainless flexes less than aluminum, so those props behave a little like a steeper pitch, so your 9 pitch ss prop may behave more like a 9.5 pitch.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Cool thanks for clearing that up. I suspected a stainless prop would flex less but I wasn't sure how that related to pitch change.

I can definitely tell how a stainless prop would be more efficient. The one I put on is like a knife. Also it's much thinner than the aluminum ones I have. I'm still shocked that I had a 10 all along and didn't know it. Never even occured to me to look

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

The stainless prop is unbelievable Paul. I could have never fathomed the difference it would make. Going from a 10 pitch aluminum to a 9 pitch stainless actually pushed me up to 22mph tonight..........and it did it in half the time. Not only did I increase my wot top speed but the torque is instantaneous now. The second I put the boat in gear tonight and tipped the throttle in I could feel the difference. It practically jumps onto plane now.

Needless to say I don't think the 10 pitch was a good prop for my engine/weight combo. Actually I know this is the case now. I really did get lucky, stainless props are not cheap but I am so happy I have one now. I dare anyone at the launch to laugh at my 18hp with a ss prop.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Dang it Paul, the very second I was happy with the engine again a new issue arose. Now it won't crank

Gear selector in N, turn key on all is normal. Turn key to crank and there is an audible beep from the gear box. Tried wiggling the lever around with no change. If the lever is in F or R when I turn the key on it beeps the same.

Rope start was hit or miss. Sometimes the engine would rope start effortlessly and one other time I could not pull the rope at all like it was in some kind of lock mode.

edit - The cable that is on top of the engine that locks or unlocks the ability to rope start appears to be out of adjustment. When the shifter is in N it's not releasing the lock all the time, This could be part of the problem but it seems to me like it might be caused by something else being out of adjustment. Atleast for the time being I know I can rope start it

 

[pvanv]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

The lock cable may need adjustment, or the lock mechanism may need repair. Some just do away with the safety lock (not advisable on a small light boat, as starting in gear could be a dangerous surprise). The starter lock went through a redesign in late 2007, which improves durability. If you decide to repair it, be sure your dealer refers to Tech Bulletin 07-006US.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

I may just do away with the starter lock all together. I need the key on to start the engine anyways and if it's in gear the warning buzzer lets me know.

It pushed me and a passenger to 20mph on the water tonight. The stainless prop makes a hell of a difference. So does playing with trim angle, much more than I ever thought.

 

[Star]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Ditto on that ss prop, I get funny looks at the ramp too. I put a Solas on my silly 15hp 4 stroke..... What a difference! Steelspike feels that the added cost isn't worth it. Repairing it will be much more difficult, so I am much more carful around rocks. The cost was $40 over a standard Alum. I get close to 23mph at sealevel on a 14' aluminum.

 

[msaunoras]

Re: 2005 18hp Nissan 4 stroke blowing oil out of the intake

Yeah I know. I'm so happy with the stainless prop but I am going to have to be more aware now. I fish one lake that is a little heavy with stumps/submerged wood. I haven't damaged(or even dinged) my prop in 5 years but I saw someone hit a stump at full speed this year already.