60hp clamshell problems and parts

chewy · 17 August 2009, 21:06

Had the SR4 out today.
Fresh fuel and engine started fine. Goes into gear and runs ok upto half throttle where it dies. Its the same forward and astern.
At one point it did manage to run through the rough spot to WOT and it was ok, did this for about half an hour then played up again.
Revs freely in neutral and starts first time after it dies.

Cleaned the filter and the line going to the engine. Plugs were wet when removed.

I'm planning on changing the plugs and leads and seeing if this help?
Anyone got a contact for clamshell parts?

9D280 · 18 August 2009, 13:33

Mine went from running like a hobbling dog to quite smooth with a new set of plugs & leads.

Was running nicely for about a minute - bummer about the spark advance & the ensuing bang.........

Mine also ran fine at idle as well before the change. On the original leads, check where they come out the coils - the corner is really sharp - one of mine had about 4 strands of copper actually left intact.

Not had to buy any "obscure" parts yet, but when I was talking to Uncle Al at Barrus he was convinvced he could source any new gaskets / fuel pump / water pump parts I needed. So I guess any Merc dealer for the "consumables" (Gaskets etc). Mitchells in Glasgow have stuff like that, and what they don't have they can order. Someone on Ebay on the south coast was breaking one about 6 months ago, although it may have been a 70 ...

chewy · 18 August 2009, 22:00

Just spoke to the local Mercury dealer... £70 for three HT leads, getting my brother to make some for a crate of Stella.

Trying new plugs and leads tomorrow along with cleaning the carbs, well my brother is.

9D280 · 19 August 2009, 09:33

£70?????

errr £15.90 for three at my local Auto factors......

chewy · 19 August 2009, 10:11

Quote:

Originally Posted by 9D280

£70?????

errr £15.90 for three at my local Auto factors......

Struggled to find one that would do them, hence I've enlisted younger brother to fix the whole thing for 36 bottles of Stella (that includes making the frame for my hatch too).

Jizm · 19 August 2009, 17:38

Just make sure he drinks the stella AFTER he does the job....

chewy · 19 August 2009, 17:54

New plugs in, shot a load of carb cleaner through check the leads and its still fecked.
Its now in the local boat yard as I go back to work tomorrow so hopefully they will sort it?

I personally think it could be the Flux Capacitor, but no one seems to stock one for a mid eighties clamshell?

alystra · 19 August 2009, 18:26

Quote:

Originally Posted by 9D280

£70?????

errr £15.90 for three at my local Auto factors......

I've been thinking about changing the leads on my engine and gulped at the price from Mercury. Thought I'd be able to get some made up cheaper. Except...
1. They have a screw thread to fit into the ignition coils.
2. Looking at the manual, each lead has a very different resistance specification.

Maybe the resistance is a function of the lead length and it's just standard plug lead stock. Perhaps each plug lead really is a different spec. Maybe it's a red herring. Any thoughts?

I must say that since I've been working on my engine myself, the engineering seems rather more subtle than is first apparrent and I wonder if this plug lead thing is another case in point.

9D280 · 20 August 2009, 08:42

Alystra,
Interesting. How much of a difference? I guess if you are running a 4- stroke it's going to be realtively new & high tec - I would have thought that for that you would need to have different sized coils - are they differet betwen cylinders.

The clamshell is good old "ram it in / friction type of HT connectors, but at the same tiome it is also a lot less high tec than yours is!

Chewy,
With wet plugs & new electrics My next suggestion was going to be the carb float(s) allowing too much fuel through at Mid range, but I guess too late now.......

alystra · 20 August 2009, 11:54

Quote:

Originally Posted by 9D280

Alystra,
Interesting. How much of a difference? I guess if you are running a 4- stroke it's going to be realtively new & high tec - I would have thought that for that you would need to have different sized coils - are they differet betwen cylinders.

The clamshell is good old "ram it in / friction type of HT connectors, but at the same tiome it is also a lot less high tec than yours is!

Chewy,
With wet plugs & new electrics My next suggestion was going to be the carb float(s) allowing too much fuel through at Mid range, but I guess too late now.......

Spark plug lead resistance.
Cyl. 1 4500 - 10700 ohms
Cyl 2 3300 - 8000
Cyl 3 3700 - 8900
Cyl 4 4300 - 10200

Replacement recommended if outside those limits. The engine is year 2000, the last of the carbed 90 4str., so it's not ultra high tech. It's CDI, but not quite in the 'computer age'. There are two identical ignition coils, each feeding two cylinders. I haven't checked the wiring length yet to see if there's a direct correlation between length and quoted resistance.

The screw threads are to allow the leads to be changed. The smaller engines of that era have the coils and leads as one piece units (according to the book). I'll be investigating over the winter.

PeterM · 20 August 2009, 11:58

Quote:

Originally Posted by chewy

I personally think it could be the Flux Capacitor, but no one seems to stock one for a mid eighties clamshell?

Thats clearly the problem - its only supposed to kick in at 88 mph - its interfering with the normal spark mid range ............

9D280 · 20 August 2009, 12:27

...which is 76 knots (it's a boat) - no wonder it's not working!

Alystra,
How are they paired? Is it the low res. ones together & vice versa, or a low & a high per coil? My train of thought here is that if they are matched in resistance then you'll get equal spark on both plugs of a pair, if one of each, the lower res. lead will take more of the charge as it;s an easier path, and mean the high res. one is starved of charge...... Are your leads of a length you could swap them so the two high & the two low re. leads are hanging off the same coil?

Screw in leads sounds like a high tech version of mine. (i can replace the lead & leave the coil in place) I could be cynical and say it's on a similar theme to the Clamshell flywheel removal thread - really obscure old American thread so you can't just go out & buy a bog standard puller......

Chewy,
How did you check the leads - what seems OK at low voltage DC (i.e what your multimeter uses to calculate the resistance) becomes a whole different kettle of fish when you start to throw high voltage high requency AC at it. As an example when I checked the insulation resistance of my old spark plugs on the Yam were "open circuit" (i.e nothing wrong) when I prodded them with the multimeter. Then borrowed a Megger - at 1000v DC, one of them had about 150ohms insul. res. (i.e gubbed) One new set of plugs later & it was like a new engine. The same could be happening with your leads.

chewy · 20 August 2009, 14:14

True I did only use a multimeter.

I'm back at work now so its I'll see what the yard come up with?

REN_RIBNET · 19 April 2010, 21:26

Did you ever fix it? If so, what where the problem.

I have the exact same symptoms as the ones you described in the inital post.

R