Mariner 15 2-stroke carb and fuel pump overhaul.

[Fenlander]

Following on from the thread where I took the carb off my 2004 Mariner 15 2-stroke to investigate fuel "spitting" due to perished breather/balance hoses I thought as it was off I might as well get an overhaul kit.

Well actually at first thought I might as well just do the fuel pump diaphragm which should have cost about £6 looking at comparable ones for other outboard types online... but Mercury only supply them as part of a full carb gasket/overhaul kit for this model outboard... so that cost me about £55!!

Appreciated Max's referral to Black Dog Marine for parts... they and Pacer Marine on Ebay were close to the same price. However postage was free with Pacer Marine but Black Dog relate their postage to item price and there was no way I was paying over £7 postage for a small light Jiffy package that in reality would have been about £1 to send. Pacer Marine's service was first class with same day dispatch and quick postage. Sent the right part too which always helps!

So the gasket/overhaul kit arrived this morning...

[Fenlander]

You get all the gaskets for the carb and fuel pump plus the fuel pump diaphragm and the starting primer pump diaphragm on the blue rod with its top seal, bottom plug and small spring.

Annoyingly there were 2 gaskets and a light rubber diaphragm that don't seem to suit anywhere on my carb. Annoying as it seems 3 of the approx 10 items weren't for my model and I'd rather they were left out and a £17 discount applied!

[Fenlander]

So I got to it and took the fuel pump and very simple carb apart. I was really pleased to see the float bowl hadn't a spot of dirt or corrosion in the bottom (see image, before it was cleaned). The rest of the carb innards were just as clean.

[uncle al]

Just a tip, but a common mistake, make sure that you fit the correct carb flange gasket when you refit the carb.

[Fenlander]

Mine's an odd one. There is a paper gasket in the set that matches the reed side of the main carb flange but there wasn't one fitted. Mine has a rubber straggly shaped O-ring thing that appears to be bonded to the carb side of the reed block where the carb bolts on. Thankfully that is in perfect condition.

There is also a second gasket in the set that 90% fits the carb flange but it fails to correctly allow for the offtake for the vac/balancing hoses and would cause an air leak if fitted.

I'll do some pics in a moment.

Just a few comments on what I found with the carb once stripped...

As mentioned above it was pleasingly clean but it will get a good squirt of carb cleaner in all the jets/orifices. The fuel pump diaphragm was not too bad but probably original so no harm in swapping it out after 11yrs. The starting primer diaphragm was hardened and would probably have split before too long... also its rubber at the top where the blue plunger comes out was hardened almost like plastic so not providing a proper seal (both of these parts were in the kit).

One big mistake I only just avoided. When you take the bottom plug out from the primer chamber there is a spring and tiny ball. You get a replacement spring in the kit but not the ball and it was only by chance I saw the ball as it rolled across the bench heading for workshop oblivion.

Slightly blurry pic of the ball...

[Fenlander]

Thanks Al for making me look at this again.

So here is a picture of that odd straggly O-ring type seal which looks bonded to the reed block flange and is the only seal I originally had between that and the carb flange.

Also a picture of a paper gasket in the set (one I thought was spare) put into that position and it does have all the required shape and cut-outs etc.

Also same gasket put against carb flange and it again would work fine.

But why didn't I have any paper gasket when I took it apart... and should the paper one be used in addition to the rubber one when you do a carb refit??

[Fenlander]

And here is another spare gasket that was in the set which initially looks a good match for the carb flange but note it would not seal all round the area where the small brass stub offtake is.

Might this be the "incorrect" gasket you might use by mistake??

[spartacus]

Manufacturer gaskets are a licence to print money. Having said that - they're money well spent for resolving numerous issues with vacuum, pump, fuel, combustion, etc.

I'd have thought that paper gasket should be applied over the embedded rubber seal. Suspect who ever had the engine before didn't use it at strip down. They probably looked up the price of gaskets!

[Max...]

I've made my own (a set of different half a dozen mixed thickness gasket paper is only a few £ on eBay) for simple templates like the thermostat but that one is a bit tricky to cut at home...

[Fenlander]

>>>Manufacturer gaskets are a licence to print money. Having said that - they're money well spent for resolving numerous issues with vacuum, pump, fuel, combustion, etc.


Yes that's where they get you. Seems a lot of dosh so you think do I really need them... then you think of possible running issues in the middle of a 2wk holiday on the Scottish west coast so you can't not get the proper set.

At the moment I'm inclined to fit the paper carb-reed block gasket as it would add to the sealing if the carb flange isn't totally flat which can happen over time with bolted down alloy flanges.

Like you Max I always had gasket paper to hand for stat housings and similar, particularly as we spent some 20ys running 20-40yr old tractors. Everything was a good size on them and a scalpel plus hole punches for the stud holes sorted many gaskets to save buying.

Max when you get home tonight is your Mercury easy to access and have a look if you have that paper gasket between carb & reed block? It would be obvious if you have as it is slightly larger than the flanges in places and you would see the edges. Only if it's no trouble.

[Max...]

I know now it doesn't have one, had it apart a Few weeks back.

Have you checked the online workshop manual? This is where buying from Black Dog comes in as I'd ring them up and ask! When I did the Merc impeller they were very helpful on the phone with inside tips/knowledge that the mechanics have.

[Fenlander]

So did you just have that straggly rubber "O-ring" bonded to the reed block?

[Max...]

Yes, same thing IIRC.

[Fenlander]

OK thanks. I'll check the carb flange on a flat surface and if it's totally true I'll have the choice of putting it back as it was or adding the paper gasket.... still likely to add the gasket.

[Nos4r2]

What might help is if you check the parts microfiche for your year-it should be visible online at Merc's website. It'll show you if/where/what gaskets are used on your particualr motor.

[Max...]

Originally Posted by Fenlander

OK thanks. I'll check the carb flange on a flat surface and if it's totally true I'll have the choice of putting it back as it was or adding the paper gasket.... still likely to add the gasket.

How about a tiny bead of silicone or liquid gasket?

[uncle al]

Max silicone/liquid gasket NO! I would use the paper gasket if the carb flange wasnt straight, so when you fit the carb do both side up equally so it doesnt either distort or brake the carb flange.Some I have had to use the paper gasket and some I have not.

[Fenlander]

Yep silicone would seal but if by any long shot you needed to pull the carb off because of a problem at sea or while on holiday a paper (or just the original embedded rubber thing) gasket is easier to deal with than cleaning off silicone and applying new on assy.

Nos yes the parts book does show a paper gasket. The detail is not good enough to see if you had a new reed block if it would come with the embedded rubber seal on the carb side like my original. Perhaps they have made that a plain flat face now so it needs the paper gasket hence it being listed.

[Rover310]

Originally Posted by Fenlander

... Annoyingly there were 2 gaskets and a light rubber diaphragm that don't seem to suit anywhere on my carb. Annoying as it seems 3 of the approx 10 items weren't for my model and I'd rather they were left out and a £17 discount applied!

Yeah, the manufacturers do that to cover more model variants under a single part number, since the majority of parts in the kits are common to a number of models. No doubt dealers like having fewer carb kits that they need to carry in stock.

[Turbodiesel]

Hang on a minute! We don't charge that much for postage! If the order is over £100 it's free delivery otherwise for Ribnet net members it's usually £2.00 for next day delivery! Not sure who have you that info!