1993 Johnson 90hp - Oil queries

[sixdeep]

You guys helped greatly sort some issues a year or so back so I'm here again to find some answers.

I've got a 93 Johnson 90hp v4. It seems to be that its using more oil than it should. I'm suspecting its about double (I've only just started noticing its excessive) The remote oil tank doesn't have markings so I cant sure either. Anyway when I got the boat the fitting on the tank turned out to be leaking air and was causing the motor to stall all the time. I eventually diagnosed that after replacing the fuel lines and primer bulb. It had a weird quick connect fitting that was a non standard thread into the tank. I've been using a Suzuki tank fitting with a 1/4 NPT thread into an adapter into the tank. That solve my problem of the air leak and stalling.
Fitting image here.
http://www.smartmarine.co.nz/images/products/xlarge/200138_suzuki_new_fitting.jpg

I noticed last weekend that the oring on the tank fitting had perished and was lodged in the line fitting. I removed that, connected it and there were no leaks so I figured it was ok. I've taken it on 2 pretty big runs since and the motor ran fine apart from one leg to a new fishing spot where it seemed to run rough. It was fine the next time after i reprimed the bulb. The motor smokes a bit at idle.More so at cold but still does it at warm. Other than that i havent noticed any sign of excess oil use. I'm going to try a plug chop next time i have it on the water to check that out.

Since I took note of the oil usage as I'd filled the remote tank and it was half empty on return. Trip was about 60kms and i would have used less than 50L of gas. Since researching caused of excessive oil use i've found air leaks can cause the vro to pump more oil than the correct ratio as there is actually less fuel in the mixing bowl. I thought initially i need to replace the o ring on the tank fitting. Then researching that and doing some measurements I found i've been running the 11mm (7/16th) fitting which are meant for less than 75hp motors.

So my question is would running a fitting that's smaller than recommended also cause a problem? I'm sure now if it had an oring it was there for sealing so it's probably leaking to some extent but i'm wondering if i need to replace it with the larger tank and corresponding line fitting?

Or should i replace it with the evinrude/johnson style?
http://www.smartmarine.co.nz/images/products/xlarge/33477_male_outboard_fuel_tank_fitting.jpg

My additional oil question is type. I've been running quicksilver 2 stroke premium plus. The guy at the local boat shop sold me a mercury labelled bottle once and said it was the same thing rebranded. I've since noticed Johnson XD30 XD50 available. The website said you can run XD50 in an older carbed motor like mine and get decreased smoke etc. Other things i've read suggested to just run XD30. What are peoples thoughts? Forgive me for i havent searched for that question i just tacked it onto the end of my major concern.

Apologies for the novel but more info is normally better.
Thanks in advance

 

[emdsapmgr]

Not sure just what your pictured fuel hose barbs go to. The Suzuki and Bombardier hose barbs look like fuel fittings. The actual oil line to your VRO fuel pump is clamped in place-directly onto the pump. No quick disconnect fittings. So you've indicated heavy oil usage, yet you have pictured fuel fittings-so your statements really don't connect with each other. It is possible that you have an internal VRO fuel pump problem/leak which could cause excess oil usage. The fuel hose on your 90 hp will work fine with a 5/16" (or 3/8") fuel hose. The oil line from the remote tank is special yellow-stripe Bombardier hose, made for oil only-it is 1/4" hose. The XD30 is the basic Bombardier 2-stroke oil. I do like the XD50, which is an upgraded synthetic blend and will burn cleaner. The XD50 also has a Carbon Guard additive which reduces carbon buildup inside the combustion chamber and esp around the ringsets on the piston. A nice feature. I use the XD50 on all my engines from 70 hp to my 2.6.

 

[WernerF]

Be sure about your oil consumption. Mark the oil level on the tank with a pen. Mark it in the middle of the front or aft area to compensate for heeling. Run the engine until you have burned about 50l of gas. Then fill the oil tank again up to the mark you made before. Determine the amount of oil (and of course of gas) you needed and calculate the ratio.

Any leak in the fuel lines (upstream or downstream the VRO pump) can cause the VRO pump to make more strokes and thus increase oil consumption.
Look for fuel-wet spots.

 

[sixdeep]

emdsapmgr - The reason i posted fuel pictures is because from what i've read and as Werner described leaking fuel lines can cause the oil consumption issue i explained. I'll try out XD50 and see how it goes thanks.
I think i'll replace the current fittings with the larger ones and recheck everything for leaks

 

[sixdeep]

Resuming this as its summer again and i'm using the boat. Same circumstances with the oil usage, It seems to be running roughly double what it should be i.e 25:1. I would have thought this would cause the engine to not run too well or smoke excessively but it seems to run great. It does smoke when idling but other than that its reasonably good. I'd prefer less fumes but im still working through the large pack of XD30 i got then i think i'll try XD50.
I checked over the hoses in the engine from the connector to the VRO. They are all OMC original - 1993. None seem to have holes but the carbs do look rather oily like there is a leak perhaps? I noticed that the clamp on the pulse hose to the VRO wasn't very tight. Probably not sealing correctly. I'll replace that with a better one but could this cause the over oiling? Most things i've read only point to fuel hose leaks. Also a boat mechanic mentioned to me once the diaphrams can get a hole which can cause issues?
Appreciate any thoughts

 

[flyingscott]

XD 50 is not going to solve your oil usage problems will just cost more. Check all the clamps and hoses on the VRO pump replace as necessary. I replace the factory plastic clamps with oetiker clamps.