Smokey 8HP mariner OB

[Yes Dear]

Hey there,

I have taken ownership of a 1998ish 8HP Mariner that goes well but is quite smokey.

When running up the river it goes really well but at idle quite a bit of smoke blueish in colour.

There is black oil stains down the back ports as well.

Starts easy and has enough power to keep me happy.

Comp is around 70 on each cylinder.

Rings or carb needs a clean and setting?

I put new plugs and fresh fuel 50/1

Any tips?

Cheers.

 

 

[noelm]

The only oil in that motor is what you put in the fuel, no amount of cleaning will help. Make sure the choke is fully off. Old two strokes don't like low speed, they tend to oil up, give it a good fast run before putting it on the trailer.

[Yes Dear]

might try a carb clean and see how that goes.

seems to smell rich when running 

was going to try some low smoke 2 stroke oil as well.

cheers 

[XD351]

If the motor starts easily and runs ok then leave the carbs alone.

Some oils smoke less than others , Yamalube is ( I feel)better than the Penrite I currently use and I have heard that Gulf western is better again ( can’t confirm this as I have never tried it) . What is the correct oil ratio for that engine ? Some engines can run 100:1 others like my 3 cyl Yamaha must run 50:1 as the middle cylinder runs hot . All two strokes smoke - it is ther way of letting you know all is well , when they stop smoking things are going to go bad real quick 🤣

 

[big Neil]

I'm with XD351 on this post. If it starts easily and runs well, accepting that 2 strokes do run "smokey", it appears to be ok. As mentioned, ensure that you have the right fuel/2 stroke oil mix. My Yamaha 15HP runs on 100:1 and it smokes at times.

If it ain't broke, it don't need fixin.    bn

[dunc333]

what about running some synthetic or semi synthetic 2 stoke oil in her less smoke more power but it is abit more  expensive amsoil brand could be the go. or as noelem said give it a good flogging if you do alot of idling cheers dunc333

Edited June 14, 2023 by dunc333

[noelm]

Do you have the owners manual? if not, perhaps look for an online one, lots of those smaller HP two strokes around that era were 100:1, but just check to be sure.....that's around the time anti pollution laws started to come in for outboards.

[XD351]

The Yamaha oil doesn’t state if it is semi or full synthetic - it just states low smoke with low ash , the Penrite I use is semi synthetic but a full synthetic is available , Gulf western is full synthetic (maybe why it apparently smokes less ) Don’t fall for the trap of thinking you can run a full synthetic oil at 100:1 in a motor that states 50:1 is to be used just because the oil bottle says it can be used in motors that are designed to run at 100:1 , don’t dump synthetic oil into a tank containing semi synthetic or mineral oil or visa versa - had a mate do that on his motorcycle- the oil went like little balls of rubber and blocked everything up . Start with an empty tank ,line and empty carby if you are going to switch to full synthetic.

[noelm]

Yep, mixing oils can be fraught with danger, don't know what those little "balls" are, but it's very common.

[XD351]

Neither do I but my mate spent the best part of a day tearing down the entire fuel system on his motocross bike - only needs one tiny bit of that stuff getting sucked into a jet and his race is over. 
Every time I start my Yamaha at the ramp people stop and look-I swear they think my boat is on fire 🤣🤣🤣

[JustJames]

Smoke is in the nature of a 2 stroke.

 

Your compression may be a tad low, but if the motor starts easily and runs OK I wouldn't lose any sleep over it, especially if you are seeing the same compression on both cylinders.

 

As a small outboard with 25 years under its belt, I don't know that I would bother to look at replacing rings, as I suspect there will be other wear apparent when you tear it down.  Use it and factor in that it may need replacing at some stage (or it may continue for another 25 years).

 

Re: Oils.  If you are contemplating a change in oils, see how the 2 oils mix.  If they mix together with no issue, then they can be expected to mix together in fuel too.  I wouldn't expect any power increase from changing oil brands or types.  The oil is there to lubricate, so it's hard to see how changing oil can find more power.

[Yes Dear]

it does idle a bit but I mainly do small 5 minute sprints to next fish spot in the river.

It runs great on full throttle, idle is a little rough but OK.

I was interested in the black dripping oil stain out the 2 exhaust ports at rear of motor and in water when flushing in bucket

looks like an excess of oil in fuel mix but i know its at 50-1 

I will try some low smoke oil and give it a flogging next time out

fuel air mix screw is an easy tune, screw in till starts to idle rough screw back out till idles rough screw back in 1 -1.5 turns, this is what I read online, happy to be correted

I will pull the plugs and see what they look like as well

I have a 2000 Johnson 9.9 spare as well if things go pear shape.

 

thanks for all the input gents

 

 

 

 

[Yes Dear]

an update

pulled carb apart found the choke check valve ball bearing is missing and the diaphragm pin was bent and missing it's port.

also found fuel in carb float, not much but replaced anyway.

New carb kit fitted and all is fine now. 

next to no smoke now and no oily unburnt fuel from exhaust.

info may help some one else.

cheers

[noelm]

It’s amazing how many times a choke gets stuck partially on, or somehow broken, it’s one of the first things I check.