Sand in carbs ?

[PajDiver]

Hi,
Newbie poster here but read many great posts over the years!

We have a Mercury 60hp 2 stroke which had to have a full carb clean and rebuild, cleaned tank, new fuel lines and a fuel filter/water seperator fitted last June after e10 fuel had damaged the fuel lines. We now only run on e5 and it ran very nicely on 4 day trips. The last trip was eventful running out of fuel towing another boat and we had to use the spare jerrycan which should have had e5 as well.

We winterised the engine by removing the fuel line whilst running on the ears. We ran up the boat on the ears in May, started fine and idled ok. We then took it on a trip and it would not idle once warm and when in gear it would keep stalling or revs would suddenly race up and down.

We then drained the carbs which came out clean, checked idle and timing and again it idled ok on the ears. We then tried a second trip and the same symptoms reappeared. We managed to make it back to shore by getting into reverse and it did not stall at 1200 revs. We stripped the carbs and found all three of them full of a sand like grit, blocking one of the jets. The guy who cleaned the jets said he could taste salt when blowing the jets.

Any ideas on what this grit is and how to prevent it in the future ?

Thanks
Alex.

[Steve509926]

Hi and welcome,

Just a thought - is your jerry can made of metal? Could it be rust?

[PajDiver]

Yes, in this case it was metal jerrycan. We filled up via funnel with a mesh filter. Do you think grains this size could get through the fuel filter/water seperator ?

[Steve509926]

I can't answer that as I've never used one.
Reading through your post "everything ran very nicely" until you ran out of fuel. So, IMO, it stands to reason it is either your tank, which you had cleaned out last year or the Jerry can.
I'd start with the Jerry can, very easy to check if it's a bit rusty on the inside.

[PajDiver]

Not sure if we have access to that jerry, will have to check.

[Pikey Dave]

That sand could be fuel varnish from old fuel that's been sat in the carbs & got dislodged by the new fuel passing through. What size/quality is your filter? where is it in the fuel line?

[PajDiver]

It has an existing small filter WS 35-816296Q2 which was changed last June and the new filter / seperator WS 35-802893Q4 which is mounted on the transom.



If the carbs were stripped and ultrasonically cleaned last June and we have only used e5 since is it still possible for varnish to form ?

[Fenlander]

When you say last June is that June 2023 or this June?

[beamishken]

Originally Posted by PajDiver

It has an existing small filter WS 35-816296Q2 which was changed last June and the new filter / seperator WS 35-802893Q4 which is mounted on the transom.



If the carbs were stripped and ultrasonically cleaned last June and we have only used e5 since is it still possible for varnish to form ?

I'd agree with pikey Dave that grit has been forming in carbs left standing for decades I doubt sticking to e5 will alleviate the issue totaly. I think it's more to do with small quantities of water drying out with the fuel when stood. Good filtration helps but it's almost inevitable you'll need to clean carbs from time to time.

[PajDiver]

Sorry, meant June 23. Forgot we are in July already!

[willk]

Originally Posted by PajDiver

If the carbs were stripped and ultrasonically cleaned last June and we have only used e5 since is it still possible for varnish to form ?

Are you asking yourself a question perhaps? Did you see the job being done?

[PajDiver]

Originally Posted by willk

Are you asking yourself a question perhaps? Did you see the job being done?

Haha, no we had a boatyard do the service and remedial works including the carb strip and rebuild. A very expensive job hence we are keen to work out why the carbs have clogged up again and what we can do to prevent it.

[PajDiver]

Originally Posted by beamishken

I'd agree with pikey Dave that grit has been forming in carbs left standing for decades I doubt sticking to e5 will alleviate the issue totaly. I think it's more to do with small quantities of water drying out with the fuel when stood. Good filtration helps but it's almost inevitable you'll need to clean carbs from time to time.

I assume though we would not expect to have to clean the carbs after just 4 day trips now we have a water seperator fitted as well. How could the water get in the carbs ?

[beamishken]

Originally Posted by PajDiver

I assume though we would not expect to have to clean the carbs after just 4 day trips now we have a water seperator fitted as well. How could the water get in the carbs ?

Your less likely to have problems if you do 40 trips in a year than you are doing 4 trips. It's the sitting idle & fuel evaporating & moisture causing corrosion in the float chamber that causes the issue.
As for where the water comes from , you get condensation in via vents & filling with cans on damp wet days or just salt spray on tanks & vents leads to moisture being almost inevitable in boat tanks. Cleaning carbs shouldn't be a particularly expensive exercise & is a job that can be done by a reasonably competent diyer

[tinker]

Originally Posted by beamishken

Your less likely to have problems if you do 40 trips in a year than you are doing 4 trips. It's the sitting idle & fuel evaporating & moisture causing corrosion in the float chamber that causes the issue.

I have this problem,.lack of use. There's fuel conditioner you can use, I haven't, is it any good? Seems expensive if you have a full tank.

I tend to start the engine every month run it for a 20 minutes. If all else fails, strip and clean carbs at the beginning of the season.

[Fenlander]

I think however annoying this problem is not entirely unexpected given the dual factors of very intermittent use and fuel from a metal jerry can. I hope that's been dumped now.

Re the moisture in fuel/carbs as Ken says on the sea there are multiple access points into fuel for salt laden air or actual moisture. Even to the point that carbs themselves are vented to air and in extreme circumstances I've had salt spray drawn into a carb through the vent not stopping the motor on the day but ruining the next run out after the salty moisture had messed up the jets/passages while the motor stood unused for a month or two.

Re the conditioner Tinker mentions I've used it for years and not had next season fuel issues but of course now I swap to Aspen for the last run of the year so the conditioner's not needed.

[User name]

That's probably years worth of deposits on there that eventually got disturbed and clogged up. People will run the carb dry at the end of the day to prevent stale fuel from sitting in there and building up crud, but it also draws in air and that might be moisture laden, so water eventually makes it way in and condenses.

When it comes to running carbs reliably, the only thing to do is budget for a good cleaning every couple of seasons or so, or learn how to do it yourself. It's not hugely complicated to do but some motors require a lot more work to access them than others.

[jeffstevens763@g]

Originally Posted by Pikey Dave

That sand could be fuel varnish from old fuel that's been sat in the carbs & got dislodged by the new fuel passing through. What size/quality is your filter? where is it in the fuel line?

Set fire to it with a small flame varnish will burn away sand won’t

[PajDiver]

Thanks for all the great feedback. Original jerry is probably not available and the grit has been thrown away but plenty of good ideas to prevent in the future.