Skykomish E29 6:48pm, 30 March 2009
Hi Guys
Well Aeolus is back in the water, the Murcury 6 HP fourstroke fired up, ran nice and smoothly. Due to the tide not being fully in and not being able to get onto my mooring decided to motor off down the creek. Had a great trip approx 45 minutes, at a steady rate...not full power. As i approached the mooring the engine would not tick over but kept cutting out every time I attempted to closed the throttle to slow down.
Before I take the engine back to the service centre and use it to commit some illegal act on the mechanic, can anybody suggest a remedy to this problem , one that was supposed to have been sorted out at the service!!!!!!!!
Normally I would have said it was the timing.....but all the valve clearances and timing is supposed to have been checked during the service.
It ran ok when cold started almost first time, and ticked away a treat just seems a problem when warmed up.
Any Ideas???????????????
Mike A1 10 years ago
I had a similar issue but found that the engine (same as yours) would cut out after ticking over for a while. I think that the problem was caused because I lashed the fuel hose out of the way, which twisted the coupling onto the engine and let air in. No issue at high revs - I guess the pump was able to overcome the leak then.

I used to lash the fuel hose out of the way which made the problems worse - I don't do that anymore.

If your engine is cutting out immediately you close the throttle then its probably something else, but a general tip is to see if pumping the primer bulb helps. If it does then its likely to be lack of fuel.
busy home [deleted] 10 years ago
Old stale fuel left in carb varnished up the carb jets. Did you drain carb last year,?
Skykomish E29 10 years ago
Ron The engine has been in the workshop since then and been run (apparently) for an extended period by them to test for overheating so I would imagine that the carburetter would have been cleaned through with fresh fuel.
The thing was it only started cutting out after 45minutes of running, I will check the fuel line Mike, interesting that you have had a similar problem with the same engine, I was going to try superunleaded next time to see if that makes a difference to running.
But thanks anyway guys for your suggestions
busy home [deleted] 10 years ago
Sound s to me then like a bit of dirt blocking the slow running jet,
Skykomish E29 10 years ago
I hope it is as simple as that Ron
Skykomish E29 10 years ago
OH DEAR!!!! just had the phone call from the main dealer....not good infact it is terminal!!!! they stripped the carb replaced and still played up... compression test... very poor reading.... and appears to be burning oil ... they read out the options...labour for stripping the power head to investigate, replace piston.. if this was the cause , a cracked head would be terminal, could cure it could be more money down the drain, a new power head was quoted at £1400!!!! a new engine is presently £900 but going up to over £1000 at end of month.....
Checked on E bay Mercury dealer selling brand new 6 hp Long shaft with 5 year warranty £850 plus dellvery overnight £14.50.
So have gone down that option.
Will be getting the charging circuit changed over from my old engine to the new one, and lets hope that this one lasts longer than the 90 hours that my old one did. Unfortunately on checking the original engine only came with a 2 year warranty so wasn't able to claim on that
pjbharrison 10 years ago
That's lousy luck, Malcolm.
I'm just working on the engine that came with my boat, a Honda 6hp 4 stroke. It won't slow run either so I've just cleaned the carb. Just waiting for the rain to stop so I can refit it.
craig48uk 10 years ago
Sorry Malcolm, that's not what any of us need. 10 hours is usually run in time for these types of motors and first oil change around 20 hours.
90 hours is still a pretty new engine you'd think. You had it in for service over the winter didn't you? Strange that nothing was noted at that time, so you have to ask yourself was it there at service time and missed, or how/when exactly did it hapen?
A run in engine shouldn't have a problem running at 3/4 throttle for 45 minutes and you can be fairly certain it didn't cause itself damage at that point, unless the water intake was blocked by a plastic bag or something.
Skykomish E29 10 years ago
no Craig that was why I was reluctant to give the dealer the business of a new engine and went else where for it.
To be fair it was not running well last summer and I was convinced that it was overheating despite pumping water through it's telltale. They serviced the engine and replaced the impellor which had never been renewed, and seemed to be running ok (apparently), so they investigated no further.
I have to say that when I ran her up the other week it did seem to have more "ummmmpphhh" and certainly did not require full throttle like it had previously to get the boat along, It was only when it was hot that problems started to manifest themselves with the tickover.
The trouble is with labour charges so high it is really expensive to strip the engine down to investigate the low compression, and so they have you over the proverbial barrel.
The thing is I don't know what the previous owner did by way of running in, or if it was abused at all.
I will perhaps strip it down when it comes home and see if I can find out the problem , at least if I fix it a a realistic cost I can sell it on and get back some money.
Andrew Curry 10 years ago
Remember that Tohatsu is the same engine as a Mercury and Mariner only a bit cheaper to buy. How old is youe engine?
craig48uk 10 years ago
Brand new, not even passed the 10 hour mark. Seems fine just now and at least I don't need to worry about cold starts and warming the engine through too much.
Skykomish E29 Posted 10 years ago. Edited by Skykomish E29 (member) 10 years ago
mine was 2003 model but bought new in 2004 by the previous owner of the boat. Ironically it cost more than the one i have just bought!!!!
PJB Keep your fingers crossed that you are not faced with a bill for a new engine too.... but I am sure you will be fine, mine has been smelling hot and not running at it's best for a season.
One thing is for sure ... there won't be a new engine for the dinghy this year.......!!!!
pjbharrison 10 years ago
Hi Malcolm.
Glad to hear you got a replacement sorted so quickly Got the engine running after the carb clean. Runs much better but telltale is only a fast drip! The water is only warm though. Time to check the impeller as the intake is clear. If its serious then I have a real problem as we had our Budget today. With the new pension levy and tax increases we've lost over €1000 a month income. There will be no more new parts this year and sailing will definitely suffer.
Mike A1 10 years ago
That's really bad luck Malcolm.

Is your replacement engine a "saildrive"? Possibly not if it does not have the charger. The saildrive also has a lower-pitch prop but you can use the one from the old engine.
Skykomish E29 10 years ago
No Mike just a standard Mercury outboard like I thought my previous one was, I wasn't aware of the difference, in prop is this a better option?
NormanKlipspringer 10 years ago
What bad luck Malcolm. Why buy Mercury when Tohatsu is from same factory as is Mariner?
Mike A1 10 years ago
The differences between the normal and saildrive are:

1. The charging unit.
2. The prop. I think that a lower pitch prop is more efficient on a slower yacht.
3. There are two holes of about 10mm diameter drilled either side of the leg, just above the cavitation plate. These reduce the exhaust gasses going out through the prop, and make the engine better in reverse.

When I bought the same engine last year the modifications were done by the dealer.

I think that there is also a "saildrive" logo on the side of the cover but may be wrong.
Skykomish E29 10 years ago
Norman I checked out the price of Tahatsu and they are the same price that I paid for my discounted Mercury, the only people who were slightly cheaper were Marinescene but they were out of stock.
Also I know that the parts will be interchangable from my old engine in respect of the charging circuit
craig48uk 10 years ago
The Tohatsu I bought was a MFS6 Sailpro. This has the charging unit, an extra long shaft at 25" and a high torque propellor designed for pushing yachts and not lightweight dinghies.
rothwell_neil 10 years ago
I have a low hours Evinrude 6Hp long shaft twin cylinder 2 stroke currently in my garage looking for a buyer?
Skykomish E29 Posted 10 years ago. Edited by Skykomish E29 (member) 10 years ago
mmmmmmmm Shame mine is already bought and paid for and being shipped. I shall have to look into the prop situation
So can anybody advise what I am supposed to ask for by way of Prop upgrade?
Skykomish E29 Posted 10 years ago. Edited by Skykomish E29 (member) 10 years ago
right I have spoken to the suppliers of my new outboard ... they can supply a "high thrust" prop for £62 , this was inresponse to my request for a suitable "saildrive " prop to drive a 24ft one ton sailing yacht.
Now before I pay out the extra, is it worth the upgrade?

Presumably it would mean that I wouldn't be reving the guts out of the O/b to get anywhere?
busy home [deleted] Posted 10 years ago. Edited by busy home (member) 10 years ago
I was quoted £30 extra when I bought the 4 merc?
(i bought the sail drive version ) with charger in the end,,
Was your outboard down on power all along ? Chilles Johnson 5
and the Merc 4 we never use above 2/3 throttle, I.e dosent go any faster
In theory the saildrive prop will be a finer pitch (slower speed more thrust ,, like being in 4th not 5th.) so i would try the standard prop before spending £62 ,, ps the johnson is standard ,, plenty of power,, just unreliable.. pps still less than 5hrs use.!
busy home [deleted] 10 years ago
Mike can you clarify higher lower pitch against finer coarser.?
Diameter comes into it too someware?
Surely a dinghy is easier to push hence coarser prop?to go faster,
NormanKlipspringer 10 years ago
My saildrive prop on my Tohatsu was swapped by the supplier for no extra charge. I cannot comment on the effect on performance but I was advised to get the sialdirve for a yacht.
Skykomish E29 10 years ago
The dealership to be fair suggested I try the standard prop first as there is no credit for swapping the standard prop with the saildrive, they say that it may be an improvement to change so not really sure what to do, How can I tell if I have a standard or saildrive prop from visual inspection as i found a spare prop on the boat and not sure if the previous owner was thinking along the same lines
busy home [deleted] 10 years ago
There s probably a number stamped on it , !2by 12 means 12 ins foreward on one rev, 12 in diameter,
Mike A1 10 years ago
By lower pitch I meant finer pitch. I don't know if the diameter is different. Like Norman, I don't know how much difference it actually makes.

Following the advice of the dealer is probably the best way to go...
Skykomish E29 10 years ago
I spoke to the Dealer and suprisingly they are trying to disuade me from buying a high thrust prop, they say that it MAY prevent me developing full revs (?is that a problem) , and MAY not improve performance that much, all very non commital so will see haow we get on with the standard prop with a new engine developing full power, before spalshing out £60
Andrew Curry 10 years ago
I have been using standard prop and its fine. The main differance in the high thrust prop is that you will gain a bit more stopping power in reverse. I have asked the question a few times if its worth changing and no dealer or expert was able to give me an answer. So in my view if it not broken dont fix it.
Skykomish E29 10 years ago
Thanks Andrew that actually was rapidly becoming my opinion especially as it would mean a saving of £60. The old engine pushed us along fine and that seems to be with a poor compression figure so hopefully I will find the new one a marked improvement.
busy home [deleted] 10 years ago
Is there a rubber timing belt on the marc (same as honda..?
Was it changed at the service?
was it fitted one tooth out run or rotated then reset?(bending a valve)
How much compression has it got now ,
My new merc 4 needs a lot of pull ,,, More than say Linda could manage ,, dont get me wrong,,,
A weeping head gasket would not stop tickover,, (unless it was very bad) Just thinking........................Find a parts manual pics of exploded engine (no pun )
busy home [deleted] 10 years ago
Robin Curnoe Penryn advised me to have a sail drive on an achilles
when I bought the merc 4 .. I m still not sure of any advantage,, It
does not have the GRUNT of the Johnson but is smoother ..
Indicating a finer prop ???
Tohatsu recomend dropping diameter as you go heaver.. same pitch
i down loaded a n owners manual foc
Running at optimum revs is important on a two stroke for economy.
On a four stroke not so crucial but power is best at certain revs..
The americian racing boys still use 2 strokes as more power and reliabillity is obtained.They went to 4 st then back,,to 2st..
rothwell_neil 10 years ago
I would not throw that engine away as I would be surprised if it can't be repaired. Sounds to me that it is quite new and outboards last for a long time as they are not heavy duty motors. If down on compression may be due to valves or rings. Rings don't usually fail if you haven't had the head off and damaged them or if long run times or run with no oil. If it continued to run then slowed down doubt it is the rings.

I would be very tempted to take the head off and look at rings and valves. If rings then the bore will be scored or look worn, if valves then they won't seat properly and should be obvious. Either way should be a cheap fix and then you can sell the motor second hand or keep as a spare.

I come back to the way that it happened, ran OK after a service (therefore should be full of oil) then slowed down. Doesn't sound catastrophic and initial thoughts would be carb or fuel block, air bubble in line. I had an issue on my old engine because the fuel line used to go up and over the bulkhead, whenever I installed the engine had to hold the tank at head height to get rid of all bubbles in line or it used to run happily then slow down and not give full revs. Getting rid of bubbles worked.

If not fuel then has to be compression or spark. If spark looks strong then compression or timing.
Skykomish E29 Posted 10 years ago. Edited by Skykomish E29 (member) 10 years ago
Neil thanks for the advice. Apparently compression was down to 30 psi which the dealer said was pretty terminal.
They checked the valve clearances at the service, and changed the plug.
I am definately keeping the engine as conscience alone prevents me selling it on.
The problem was not that it dropped revs, but would not tick over at all. Like you ,both the dealer and I thought it was caused by carb jet problem, they stripped the carb put back together and still refused to idle, thats when they compression tested it.
The dealer was reluctant to strip the engine to examine the bores , due to the labour charges involved and the posibility of bore scoring , which would mean more wasted money.
Unfortunately I don't really know how to get the head off a four stroke to have a look at the cylinder, but am tempted to have a go.

On reading the warranty that came with the new engine there is an exclusion on the use props that fail to enable the engine to run at max revs which would explain the dealers concern in this respect.
busy home [deleted] 10 years ago
You would have had bad noises if the bore was scored . I recon a bent valve ( piston touched it) Cam belt slipped????
Check the belt timing ,,before you dismantle,, If its got one ,,
Skykomish E29 10 years ago
um wouldn't the valve problem have shown up when they checked them during the service??? bearing in mind I was having the same problem before the engine went into the dealer. To be honest they are as mistified as I am.
blueachilles 10 years ago
Not if the firm who serviced it were anything like the VW main dealer who charged me for work they blatantly didn't do.....
busy home [deleted] 10 years ago
Not if they checked them before they put a new belt on, and bent one.
I thought the original prob was overheating? Was it not ticking over before service?
Skykomish E29 10 years ago
no ron I felt that the two might have been connected as the engine was smelling hot, though tell tale was working and was stalling when throttle closed after being run for a while. These were all problems brought to the dealers attention when i took it in for a service, they did all the jobs on the service schedule which included setting the valve clearances, and adjusting the carb settings along with changing the impeller which had net been changed it appears since it was new, when run up in the tank it appeared to run well, apparently, and to be honest when I first ran her up on the boat and chugged around the marina all sounded fine, though it did take a couple of pulls to get her started and each of those required me to pull the cord out a long way, it was only after going up the creek and out onto the river and return to the marina that problem of stalling re appeared. So really I can see that they had no reason to think that they had not cured the problem. Never mind I now have at the very least a good source of spares for a Mercury 6
pjbharrison Posted 10 years ago. Edited by pjbharrison (member) 10 years ago
Hi Malcolm
Just read your original post again. The engine started up fine and ran smoothly for 45min. It then would not idle. To me, this sounds like a partially blocked jet, as others have already suggested. When first started the choke would have allowed it to run until throttle was opened for normal running. It then ran normally for 45min. It would not have done this with a bent valve. It would not have run for 45min under load without noticeably overheating after 20 min with any of the major problems listed already.
I'd check the compression again. Do you know anyone with a compression tester? Aldi had them for sale a week or two ago - they may still have some. Your local garage may test it for you or a friendly motor factor. My local motor factor rents or loans out some tools to regular customers.
Is the OB agent reliable, desperate for buisness, either sales or repairs?
One other thing, have you checked the spark plugs? You can test by removing and holding it against the engine block while turning over the engine, you should see it spark. Also, are the plugs wet with fuel when removed after trying to start the engine?
rothwell_neil Posted 10 years ago. Edited by rothwell_neil (member) 10 years ago
If the 6hp Mercury is what I think it is then it is a single cylinder pushrod engine. Technology says that overhead cams are more powerful but pushrod engines are great for DIY. The cam cover, can be removed and then you can see if the valves work when you turn the engine over and also if they have clearance when supposedly closed. The head will be easy to remove and then you will be able to see if the valves seal properly and if the bore is scored or badly worn.

Having said that i would also check the jets on the carb first as that is the first port of call. Last thing is my evinrude used to run hot and cut out even after cleaning the carb and with a perfect tell tale, blocked water passage in the head meant it got hot despite pumping water. Manuals can be bought from ebay and the following link is for up to 2003 enegines.|66%3A2|65%3A12|39%3A1|240%3A1318
busy home [deleted] 10 years ago
If the psi is 30 pulling the starter cord would offer very little resistance
120 psi would be near norm , That would be an easy check to start with,,
Skykomish E29 10 years ago
Thanks Guys A nice project to get my teeth into, would be nice to get it running properly
Andrew Curry 10 years ago
As already said have the compression rechecked. If it is low it could be a number causes.

1. A burnt out valve/ incorrect valve clearances were they adjusted at service?
2. Broken ring/scored bore ( take a compression reading then add oil through plug hole if reading increases with oil added it will indicate a ring/bore problem)
3. If engine is running check breather pipe that runs to carb. Run engine with if off if its blowing out smoke/gas this will be blow pass the rings again showing a bore/rings/piston problem.
4. Bent con rod (Has the engine been stored the wrong way allowing oil to run into cylinder and causing a hydraulic lock when it has been pulled over causing the con rod to be bent this is probably very unlikely)
5. Blown head gasket.

Other things to check.

6. Take carb apart and clean jet and needle valve for float.(this can be fitted wrong way round causing cut out at idle)
7. From local car parts shop buy a inline spark tester this will allow you to see if the spark stops causing problem at idle. I had a faulty charge coil causing engine to cut out.
8. Connect fuel supply directly to pump to rule out air problem at connector.
9. Run with new spark plug (am sure this has already been done)

Hope this is of help.
pjbharrison 7 years ago
Did you ever get the outboard sorted, Malcolm?
Skykomish E29 7 years ago
Hi sort of I took it in for repair and they diagnosed low compression ? cause so rather than pay a fortune to get them to strip it down with no guarantees of fixing the problem I bought a new engine online. As it happened I had a friend who volunteered to look at the old engine for me and he concluded that I had made the right decision
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