Merc 90 fourstroke stutter and stall - Page 2

Daniel TD5 · 01 August 2005, 15:43

andy had the same problem on my one found its was the carbs and the timing just kept stalling atb idel

see this report http://www.rib.net/forum/showthread.php?t=9700

hope it helps

dan

Bilge Rat · 01 August 2005, 16:33

Quote:

Originally Posted by Daniel TD5

andy had the same problem on my one found its was the carbs and the timing just kept stalling atb idel

see this report http://www.rib.net/forum/showthread.php?t=9700

hope it helps

dan

Dan does your motor still run, seems like years since you've had the old girl in the water, must be spiders and shit living under that hood

If your gona sell her can i have first dibs on your dry suit

Turbodiesel · 02 August 2005, 08:04

You should have one fuel pump. Its on the Rear of the engine. Its square in shape and sits on the cam cover of the head. Its run by the cam shaft, there should be no mechanical links to it, only one fuel hose in and one going out. In fact come to think of it, it might not be square in shape

. Depending how old it is. Some of them have a round ish shape one with three cross head screws in the front of it. Its not uncommon for the plunger inside the pump to stick.

ollyit · 02 August 2005, 09:43

the beast in question...

Hightower · 02 August 2005, 10:40

Quote:

Originally Posted by Turbodiesel

You should have one fuel pump. Its on the Rear of the engine. Its square in shape and sits on the cam cover of the head. Its run by the cam shaft, there should be no mechanical links to it, only one fuel hose in and one going out. In fact come to think of it, it might not be square in shape

. Depending how old it is. Some of them have a round ish shape one with three cross head screws in the front of it. Its not uncommon for the plunger inside the pump to stick.

I actually have two fuel pumps and they're square shaped, but what I was referring to was the accelerator pump. Its kind of saucer shaped and sits by the throttle cam mechanism. It has a rod comming out one side that connects internally to a diaphram which is in turn operated from the vacum created by each one of the four carbs, Turbo.

Andy

.......PS: Thanks Olly

.

Hightower · 29 August 2005, 01:50

I still haven't sorted this one out. Checked out the throttle side of things which seem fine, went out on the water and things are even worse than before!! ( and I haven't even moved anything).

Will book it into Lee's next week if I can't get a carb balancer.

Andy

Hightower · 11 September 2005, 02:01

Just an update and closure.

All those that sais Carb......Give youself a pat on the back!

I took my Rig to Dean at Hedge End outboards (07749633797) on the recomendation of a couple of RIBnet vets, left it there all day. He stripped down the Carbs and found a little crap in the top three ones and loads of salt crystals in the bottom one. He also found the two blanking plugs on the inlet manifold (ones used for balancing) had come loose.

The upshot of this is that I had a very nice trip out this evening and she's purring like a cat again.

Thanks Dean! Highly recommended, good value, Outboard doctor.

Jono Garton · 11 September 2005, 08:25

Hi

Pleased, you sorted the problem do you use a fuel water seperator style filter (the ones with the clear bowl on the botton) external to the engines filter.

Neal · 11 September 2005, 09:31

Quote:

Originally Posted by Hightower

The upshot of this is that I had a very nice trip out this evening and she's purring like a cat again.

Good news Andy Hope to see her out and about soon

Hightower · 11 September 2005, 09:36

Yes I do Jono, but not the one with a clear bottom. It's a cartridge type one, oil filter style so doesn't have the advantage of the sight bowl in the bottom.

I was told by Dean that the salt crystals where probably caused by sea water or vapor being sucked in the bottom carb which is sitting in the bowels of the engine casing, I have been suffering from a certain amount of water ingress in the coweling and seem to get it more whilst pottering around at displacement speeds. Attemps to stop this have been unsuccesful but I'll have to give more attention to this problem to prevent the Carbs from getting clogged again.

Andy

Hightower · 24 September 2005, 18:03

I'm really getting pissed with my Merc......Wish I'd stayed with the Yam!

Went out today, got water in the cowel from somewhere (think it's from stopping and the stern wave hits the rear end), anyway the stutter thing is back, it's gotta be connected!

Any Idea's guys?

Richard B · 24 September 2005, 18:24

Yes - avoid the stern wave hitting you up the stern by planning your stops!

Either slow down more gradually, or do a wiggle on the wheel before you stop, or give the throttle quick blip to "kill" the stern wave (that's the most effective).

bogib · 24 September 2005, 18:27

I am sorry to hear about your trouble Andy send me full description on the problems by pm or email and I will have word with our technicians on Monday.

Bogi

Hightower · 24 September 2005, 19:09

I've tried every trick in the book in preventing the stern wave from crashing into the transom but it keeps on comming, the most effective is a tight 180, but you can hardly execute that in every stop.

Thanks bogi, your a gent! I've E mailed you about the check valve and will compile a description about the stutter prob later this weekend.

.

slimtim · 24 September 2005, 20:42

is it coming in through where the lid meets the lower section?

Hugh Jardon · 24 September 2005, 20:51

Quote:

Originally Posted by Hightower

I've tried every trick in the book in preventing the stern wave from crashing into the transom but it keeps on comming, the most effective is a tight 180, but you can hardly execute that in every stop.

Thanks bogi, your a gent! I've E mailed you about the check valve and will compile a description about the stutter prob later this weekend.

.

how about when you slow down just keep a little bit of speed on to keep forward of the bow wave and then drop down to 0, does that not work either?

Jizm · 24 September 2005, 21:39

when you find the water in the cowl, what components are getting wet?

Hightower · 24 September 2005, 22:53

It's almost better to slow from a higher speed as there seems to be quite a large dip at say 5 knotts. The back of the RIB isn't getting swamped but it does come up above the coweling on the outboard which is what I'm trying to prevent.

The seal around the casing is intact and appears a good fit just under the coweling I can't help feel it's getting in else where. I've painstakingly gone around the seams at the back and sides of the casing with a little tube of black silkoflex but there's some water getting in somewhere!

As far as I can see the water isn't getting to any of the electricals and as I've just recently had the Carbs cleaned and the bottom one reported as having salt cystals in, I have to assume it's that one again. She ran fine last time out (with no water in cowel)! It just has to be connected!

Andy

Jizm · 25 September 2005, 09:56

So the water could be getting into the bottom carb then? Whats the seal on the airfilter like? on my engine the carbs are at the front and the air cleaner bolts onto them with the inlet at the very top. however where each bell mouth pushes into the filter there is a decent seal. Also where is the air intake in the cowling? Can't make it out from pics of your boat!

Hightower · 25 September 2005, 10:12

Well here's the thing! If water is indeed getting into the carbs surely it's going though the inlet, the same path that the air goes. Because water is heavier than air it sits at the bottom of the air box and slowly trickles into the bottom carb, possibly going into the jet area and upsetting the running at low revs.

The air intake on the coweling is at the top and rear and as far as I can see shouldn't let water in unless a stern wave swamped the outboard. Inside the cowel the inlet for the carbs (air box) is at the front of the engine with a large opening going from roughly inline with the top of the block to where the control cables enter the the rear, water could be comming though the bottom of the vent but it would have to be quite a high water level to do this or drops of water thrown around by the motion of the boat.

I'm just going out to have a further look and might takke some photo's of the layout.

Andy