2 problems needing the wisdom of the Engineers on this forum

[ontheplane]

Hi all,

We've been out on the friends boat this weekend, and have had 2 problems turn up.

1) I was driving and was stupid enough to reverse over the rope towing the dinghy. Engine jammed the rope into the prop, and it stalled. We got towed back into a pontoon. I lifted the leg and tried to free it. Couldn't free it, so I cut the rope off thinking that I could re-start the engine, and go forward & reverse to free the little bit of rope off.
Stupidly, I forgot to drop the leg before I re-started the engine - it fired, ran for a moment then died, when I went to try and re-start there was no ignition whatsoever. No power to the ignition switch or anywhere else. Power was still there to the accessories, however the voltmeter didn't flicker, no ignition lights came on, the temp guage didn't work etc.

Bearing in mind all I'd done was fire it up with the leg raised, this looks like a fuse has blown somewhere, the battery is still ok so can anyone suggest what it might be - and is it likely to be a fuse??


2) Whilst the engine had stalled, I leapt into the dinghy and started up the outboard. It started and ran, but after a short period of full throttle, it started to lose power and cough, now I'd cleaned this all out by cleaning through the carburettor. previously which had fixed the problem (or so I thought).
So - either the fuel tank is full of crud, (I'm going to run it all through a coffee filter to clean that) - or the fuel pump can't supply enough fuel at full speed. Now when I stripped down the carb, I also had to do the fuel pump, and I couldn't see any moving parts in there at all.... Now I checked all the gaskets etc, and they looked ok, but how does the fuel pump work, and I guess is there a service kit to rebuild the fuel pump, but I need to know that this is the problem.


Thanks for help on both of these matters!!

 

[Morpheous]

Got no helpful suggestions I'm afraid but can I recommend you send the story in to the MBM Confessions page - sounds like a corker

 

[landlockedpirate]

It's possible that you have just popped a fuse, or if its a mercruiser certain models wont start when the leg is in the lifted position.

With the dinghy outboard I would start with the obvious - is the air screw open on the tank, is the fuel fresh and try a new spark plug.

 

[halcyon]

With the dinghy outboard I would start with the obvious - is the air screw open on the tank,

Had same problem years ago, shortly after the outboard was serviced to add insult.

Air screw was open at the time, engine ran, then slowly died. Turned out to be the rubber washer the screw clamps on to block the hole. The screw was open, but a little round slug of rubber washer remained in the air bleed hole.

So don't assume a open screw is a open air flow.

Brian

 

[ontheplane]

Hmm that's a possible - I'll try running it off a different tank.... Certainly it has all the hallmarks of the screw closed - runs fine for a short while, then if you want full power it will only do so for a bit before dying.... throttle back and after a while it recovers a bit, then full throttle and it dies again....

Will try another tank....

 

[ontheplane]

It's possible that you have just popped a fuse, or if its a mercruiser certain models wont start when the leg is in the lifted position.

With the dinghy outboard I would start with the obvious - is the air screw open on the tank, is the fuel fresh and try a new spark plug.

Sorry should have said.

Engine is old Volvo AQ145 with a 270 leg. Started once with leg up, then died quickly, then no power to ignition at all - all the hallmarks of a fuse suddenly going BANG

 

[oGaryo]

Sorry should have said.

Engine is old Volvo AQ145 with a 270 leg. Started once with leg up, then died quickly, then no power to ignition at all - all the hallmarks of a fuse suddenly going BANG

a bit of a long shot but I had similar(ish) symptoms a month or so ago... turned out to be a dodgy battery isolation switch... auxialliary stuff would work but the ignition was dead. replaced it and all works fine now... it affected the ability to raise and lower the leg too.

 

[ontheplane]

That could be worth a look - did you get any symptoms at all - or did it just die one day?

In fairness though - this was fine one moment and then not the next - and the switch hadn't been touched!

 

[Peanuts]

Hi
A 145A with a 270 leg - thats an different set up, all the 145A I have seen are with a 280 leg.
Never mind back to your post, I assume you have checked the 4 way fuse on the port hand side of the engine block, on my old boat, every now and again, usually at the beginning of the season, turn the key - nothing! Remove the out going cable off fuse block, connect to the next connector and everything would work, but I would note it had never blown the fuse.
It might be that the next time it happened I would be reconnecting to the one I moved it from the year before.
Anyway hope this is of some help.

 

[ontheplane]

I did take a quick look at that - I checked the fuse to see if there was an infinate resistance across it - then I plugged the cable back onto the same terminal. I did think it odd that there were 4 terminals yet only one terminal was used - what are the other 3 for?

Thank you everyone for help so far - very useful.

 

[Peanuts]

They are spares, so if one blows you can quickly move the cable to the next terminal. As I mentioned I never blew a fuse just moved the cable to the next one and it worked - don't ask why it was just one of those things.

 

[jfm]

Ref 1, there's no substitute for going round with a voltmeter to find the place (fuse or otherwise) where you've lost the 12v. You have it at the battery but not at the engine/dash, so the break is somewhere in between!

Ref 2, the fuel pumps are invariably diaphragm pumps actuated by pulsating crankcase pressure. So the moving parts are the diaphragm plus two rubber flap valves. Often all these components are made from a single peice of rubber not much bigger than a 50p coin and you just need to unscrew the lid and change this piece of rubber. Very easy job. Turning to the suggestion it's a vent block in the fuel tank, to diagnose this just unscrew the tank lid soon after stopping the engine. If vent is blocked you'll hear a whoosh of air into the tank. Also a blocked vent will affect the engine's running more if the tank is quite full, and hardly affect it at all if the tank is right down to the dregs

 

[ontheplane]

Thanks jfm.

ref 2) The tank is very full, and I struggled to loosen the top at all - so perhaps that is the problem - I intend to run engine in a tank for a while, then try and loosen cap - if I hear a whoosh it's likely I've found the problem.... Also, have screwed up the vent now, I will undo it, and if I don't hear a hiss, I reckon that's a clue as well it's not venting properly.

 

[ontheplane]

Well still haven't found the problem

Update....

Undid the tank vent - there was a hiss - so that would suggest that I had opened the vent.

Then ran engine and as usual it ran beautifully for about 5-10 min and then showed all signs of fuel starvation.

So then I undid the cap on the tank - no change, engine still had the problem, even lifting the cap right off.

SO - there is no vacuum in the tank - or if there is it's not the problem. What next guys??

If it was fuel pump why will it run for over 5 min at full throttle without problem?

If crud in fuel, why is filter not full of crud?

HELP!

I am now really baffled!

 

[DavidJ]

Reminds me a little of a problem I had with my first petrol boat. The fuel line had gone porous but not enough to let fuel out, just air in and hence stopping the engine.