Engine Revs down

tonto · 04 December 2013, 13:25

I took the boat out yesterday, and had a good days fishing, however I had a perplexing problem.

On the way out it was a little lumpy, and after a bit of a slam into a swell the engine lost RPM. We were doing about 4,400 Revs, and this dropped to 3,900. This stayed like that for 5 or 10 minutes, and then picked up again.

On the way back in, it did the same thing, but did not pick back up again, it also sounded like it was running a bit lumpy, so I guessed it is probably running on 5 rather than 6 cylinders. I did not get a chance to look at it last night as it was dark and cold by the time I got home, and I am busy today, however I will look at it tomorrow.

The engine is an Evinrude 135Hp Fichte RAM engine, the BRP model.

I do have a diagnostics kit for it, but not used it before.

I was just wondering if anyone has experienced this before, and was thinking it may be a plug breaking down, or an HT lead or an Injector with dodgy wiring? Any ideas to point me in the right direction would be good!

Thanks in advance,
Gary

Searider · 04 December 2013, 13:30

Similar happened on my opti a few years ago. Turned out to be ht leads breaking down.

tonto · 04 December 2013, 13:33

Quote:

Originally Posted by Searider

Similar happened on my opti a few years ago. Turned out to be ht leads breaking down.

How do I determine if it is the HT leads, or should I just buy a new set?

Gary

Trimix · 04 December 2013, 13:36

I would measure the resistance on them, and wiggle them about. All they do is conduct the current. They wont all be broken, so if you can find the crap one you wont have to buy a whole set.

GordyP · 04 December 2013, 13:43

Would be worth making sure its not an injector, I had a similar issue with a Ficht engine, the oil wasn't getting injected into one of the cylinders with catastrophic results!

jyasaki · 04 December 2013, 16:56

Quote:

Originally Posted by tonto

How do I determine if it is the HT leads, or should I just buy a new set?

Hook it up to a hose and run it in the dark. If the leads are breaking down, you should be able to see arcing.

Be a little careful if you're going to manipulate them while the motor is running, unless you enjoy catching high voltage (won't damage you, but doesn't feel too good.)

jky

Portholme · 05 December 2013, 10:10

I had a similar thing with my opti a few weeks ago and it turned to be rough weather shaking up rubbish in the tank.

The water separator was full of water and there were black spots in the filters where the pipes were breaking down. I replaced every pipe and filter and it is as good as new.

Two unrelated thing but it was the loss of revs after a rough trip that made me check it all out.

Trimix · 05 December 2013, 12:02

With any type of engine problem - check the easy solutions first. Ive learned that from lots of wasted time.

tonto · 05 December 2013, 19:57

I just ran it in the dark.

It was a bitch to start, kept firing and dying straight away, I could only get it to run by using the fast idle lever.

I could see blue flashes where the leads were connected to the plugs, and on one lead where the lead was connected to the block, but not on the leads themselves.

I also checked the water separator, which was dry, well only petrol, anyway, and the filters look clean.

Does the above sound like I need new leads?

Also one other question, I looked and looked, but could not find the plug to connect the diagnostics lead. I did not take off the air box, but looked everywhere else! The workshop manual I have just says there should be one!
Any ideas would be gratefully received.

Thanks in advance
Gary

9D280 · 05 December 2013, 20:12

Mine ran on 2 and I found when I pulled one of the leads out the coil the connector bit stayed put!

Changed all three on grounds that where one goes the rest will surely follow...

Admittedly they only cost £7 from an auto factors.

Searider · 05 December 2013, 20:46

Quote:

Originally Posted by Trimix

With any type of engine problem - check the easy solutions first. Ive learned that from lots of wasted time.

Also check the cheap stuff first!

m chappelow · 05 December 2013, 22:13

Quote:

Originally Posted by jyasaki

Be a little careful if you're going to manipulate them while the motor is running, unless you enjoy catching high voltage (won't damage you, but doesn't feel too good.) jky

As Jyasaki just said doesent feel too good ?,
Especially if theres lots of dried up saltwater on the stuff & theres more sparks & arcs than a 1930s Frankenstein movie !,
A pair of plastic or proper Nylon pliers is great for messing about with HT leads even kids plastic toy ones ,

tonto · 13 December 2013, 17:24

Ok, looked at a few things, ordered a new set of plugs, good job too as they were not in a good shape, it looks like the electrode has burnt away, possibly indicating a timing problem.
Also the diagnostics indicated an issue with the crank position sensor, as it was easy, I took it off, and measured the resistance, which at 140ohms indicated it was not good.
When I pulled the leads off the coil, 4 of them were full of white corrosion, and black carbon from arcing.
So a new set of plugs, a new set of leads, some cleaning up of the coil terminals, and a new CPS, and she now fires up great, idles and runs smoothly, next test will be to launch her and see how she handles at speed, and with some revs!