How do I know oil is mixing

Jwmarineuk · 20 September 2013, 11:13

I have a 75hp 2007 2 stroke Mercury Outboard.

Instead of mixing the fuel and oil it has an oil tank so it mixes the fuel and oil during the injection process.

Apart from noticing the level decrease in the tank is there any other way I can know the oil an fuel is mixing properly?

Have heard of oil pumps failing and engines seizing, also heard of people doing away with the oil tank and mixing the fuel themselves to rule out the problem of the oil pump failing.

I'd prefer to leave the outboard standard and use it how it is, any advice on how to check its mixing properly would be great.

Thanks.

Pikey Dave · 20 September 2013, 13:15

I'm not familiar with your engine, is it "old tech" or "new tech" i.e. carbed or DI. If it's DI (Direct Injection) it may have some kind of electrickery that monitors the oil pulses & alarms if the oil flow is low or missing. Apart from that I dunno, sorry.

matt h · 20 September 2013, 13:44

First thing i assume its a carbed version. Monitor the oil level drop.and mark the oil tank before and after the run Secondly take the plugs out after a good run at more than half throttle and check the colour of the plugs. Should be a light brown ideally.
If there is any poss issues...you can also as a service requirement, bleed the mechanical oil pump. There is a small bleed screw on the outer side of pump and let the oil run out for 15 secs or so.the the oil should freely run and this ensures the oil filter in tank is not blocked and/or limited flow.
Tcw3 is the correct grade for that unit. I alway use manufacturers oil that is recommended as not worth it for the sake of a few squids.

HughN · 20 September 2013, 15:39

The other way is to disconnect the oil pump, run the engine on mixed petrol/oil and measure how much oil is pumped out during a given period. There is usually a "volume of oil per minute" in the spec - if you can find it.

Nos4r2 · 20 September 2013, 18:11

2007 and 75hp would make it an Opti wouldn't it?

matt h · 20 September 2013, 18:59

Im tinkin by the description its one of the last 2 smokes. Ya cannot disconnect the oil tank on a opti . Ha ha but lets wait to see what it is!!

paintman · 20 September 2013, 21:19

Always a bit of a worry. Checking the level on a daily basis is a good start. I had a split hose from the oil pump on mine recently & the only way I found that out was by a daily visual inspection - oil inside the engine cover where there shouldn't be oil. The pump & level warnings didn't pick it up & there's no reason why they would have until the tank had emptied. Without my daily check I expect I'd be in the market for a new engine - & I think I've been lucky as it is.
Mine's the older (1989) 135 Black Max with injection - really its just a metering device that adds oil to the fuel prior to the carbs - & there is a lot on the web for engines of that period which deal with disabling the oil injection mechanism & just running on a 50:1 pre-mix.
Oil injection has always struck me as an answer to a question that no-one has asked.

Jwmarineuk · 21 September 2013, 07:26

Thankyou for the replies. I'll be home next week so ill'll see if it's an opti or not.

I'd rather run it as is, than worry trying to modify it.

clydeoutboards · 21 September 2013, 16:03

Hi

Pre mixing is far safer. The commercial fishing guys love to tell stories about the poor sod who's auto mixer failed and killed the engine and to be fair it is a single point of failure that you can get rid off v easily.

steve-ribnet · 27 September 2013, 21:12

I recently re-instated the autolube oil pump on my old carbed (i.e. not opti/DFI) 100hp mariner after the previous owner disabled it for precisely the reason clydeoutboards gives. Admittedly I am more nervous/conscious about it now, but hey. It is used as a support boat that spends long stretches at idle or stooging around at low revs, so benefits from autolube as it will have less fouling of the plugs, less sooty deposits, less smoke and of course lower oil consumption.

Re-instating involved re-plumbing the oil tank ( I replaced the oil pump outlet hose with some clear hose so I can see oil/bubble flow and check for priming),then synchronising the oil pump to the carbs (adjusting the pushrod lengths to align marks on the pump), then bleeding the pump (loosen screw on top of pump 'til oil comes out bubble-free), then you can test the pump:
run on 50:1 premix, disconnect the oil pump outlet hose and the pump control arm. Hold the pump control arm in full-throttle position, run the outlet hose to a 50ml measuring cylinder. Run engine at 700rpm for 15 mins and measure the output - in my case 28.6 ml +-2.6ml at 70f outside temp (expect less oil if cooler).
Test the warning buzzer on the oil tank float switch whilst you are at it.

I worry more about the hoses carrying the oil splitting/coming loose rather than the pump failing. Your oil level in the tank would be going down as normal.....

Turbodiesel · 30 September 2013, 21:00

Quote:

Originally Posted by clydeoutboards

Hi

Pre mixing is far safer. The commercial fishing guys love to tell stories about the poor sod who's auto mixer failed and killed the engine and to be fair it is a single point of failure that you can get rid off v easily.

But if its an Opti don't pre mix it!! you will kill the air compressor!

Downhilldai · 30 September 2013, 21:57

I use a graduated syringe barrel in place of the oil reservoir and run the motor on pre-mix to measure consumption. Gives an accurate measurement and the oil pump is running under normal load ie pumping the oil into the fuel line or crankcase, rather than into an empty pot.

9D280 · 01 October 2013, 12:31

Quote:

Originally Posted by Jwmarineuk

Apart from noticing the level decrease in the tank is there any other way I can know the oil an fuel is mixing properly?

The engine will stop suddenly accompanied by a horrible grinding noise!

Joking aside, 2 thoughts here: (as someone who premixes)

1) Premix is messy. If you get even a small spill your deck WILL become a skating rink, and unless you know exactly how much premix has been used, or have a totally dry tank you can never properly guestimate where the level actually is, so will inevitably run over oiled. (which some may argue is no bad thing, but having bought a used engine from someone who thought along those lines & threw in an extra 100ml each time "to be on the safe side", trust me, too much can be a bad thing......

2) My old Suz DT25 had an oil flow switch fitted right by the injection point. It was a wee pressure activated thing held open by the oil flow. That sat in-line on the oil pipe and on "no flow" closed contacts. It was (I believe) wired in parallel to the deadman, as Ipulled the plug & shorted the terminals & the engine stopped dead.

Assuming you have a pump -hose type system, I guess you could retro fit one of these off asn old Suzi and parallel it to your stop circuit. IF your Merc is old enough, there may be a "no run when tilted" mercurey switch - that would be a simple replacement of the mercury (level) switch with the wire from the oil flow sensor.

In some respects (usually wehen filling the tank or doing a lot of slow speed work) I do miss auto mixing......

Locozodiac · 01 October 2013, 22:04

The only thing that I find positive about having a autolube system is that precisely delivers less oil when at idle and more when at wot, down issue is that if pump fails engine will severely overheat and seize.

Donw issue running on pre-mix is that standard 50:1 ratio is excellent for wot boating and much worse for idle boating as tends to foul plugs more, boater will need to live with this last one or change plugs more frequently.-

Happy Boating

Jwmarineuk · 02 October 2013, 16:43

Hi and thankyou for your replies!

My engine is carbed and not opti.

Have serviced it this week so hopefully no problems with oil mixing!

Taking it on the Water tomorrow so will run further tests then!

Thanks.