multiple problems could it be electrics?

I have twin 3l glp c petrol engines (2004) in a fairline mirage with SX outdrives. Boat had been working well with some longish trips. Then my son went to start the port engine and it turned over and caught until ignition released and then it died. After recharging the battery and with some advice from Don I traced the fault to a fuse. However now the engine runs rough, is hard to start and backfires. On tickover it can run for 20mins or more and will rev high in neutral but under any load the revs die and the engine cuts out, often with a backfire. Could the blown fuse be related to some other electrical problem causing these symptoms. Until the fuse blew the engine ran well.

Meanwhile on the starboard engine I have suddenly started getting very high oil pressure (off the scale) when I increase the revs. I have a leaking raw water pump (water getting past the seal and into the housing) and I know I ned to renew the pump. I have checked to see if there is water in the oil but it is fine and the oil level is normal. Could the leaky water pump generate the high oil pressure? In addition the trim gauge is reading fully up when the sterndrive is in the down position and the trim switch has stopped working.

All these problems seem to have occured at once. So I am inclined to think the high oil pressure, the trim gauge reading and the failed trim switch plus the problems with the other engine are all related. I just find it strange though that it is the guages on one engine and the poor starting on the other that has occured together. Perhaps just coincidence.

Any help greatly recieved

Re: multiple problems could it be electrics?

I think you still have some wiring issues under the dash, except for the pump leak. Without getting the wiring traced out and tagged with the proper color code so you know where things are at, and if they are supposed to be there, it's going to be a problem testing.

Could the leaky water pump generate the high oil pressure?

Click to expand...

No. The sender is also electric and wired to the dash, see above statement.

Re: multiple problems could it be electrics?

Don

Don

I can see how an electic short or similar under the dash could cause the guage problems and blow the fuse. But what would it now be doing to the starboard engine to make it backfire and lose revs and cut out under load? Could it be linked to an electronic choke or is there some other electrical control device that would effect the revs and backfiring?

Many thanks

Re: multiple problems could it be electrics?

Loose, poorly made connections will give intermittant power to the distributor, yes, it can cause problems.
It could very well be something else, I just gave you my point of view of your problem.
Use a mechanical oil pressure gauge on the engine to see what the oil pressure is.
Some voltage checks on the purple wire at the coil will give you an indication if things are cutting out or not.
Look at the choke, is it open when warmed up?

Re: multiple problems could it be electrics?

Don

I couldn't get down to the boat today but I read up on how to test the coil and distributor. My manual refers to checking voltage (min 8 volts needed) across purple wire (one of the purple and gray pair) and also testing the pink (one of the pink and brown pair). As I say I didn't get to the boat but I know for sure that I only have one of those pairs connected to the side of the distributor. The other position for the other pair of wires is capped off. I cant remember off hand whether I have the pink and brown of the purplke and grey pair. Can you give me any advice or point me to a post on what/how to test when I only have the one pair of wires? Many thanks

Re: multiple problems could it be electrics?

Don

If you're reading this please help! What we thought might have been connected electrical problems has turned out to be a number of unrelated co-incidences. The port engine is now running well. I did a comopression test, cleaned all connections and put new plugs in.

The Starboard trim gauge is still playing up but of little consequence at present. The big one is the high oil pressure on the starboard engine which has proven itself not to be electrical by blowing the rubber gasket on the oil filter and spraying oil into the bilges. I thought it might be a faulty oil filter so put a new one on and refilled with "cheap oil". I also did a Compression test and new plugs etc as per port engine. The plug in cyclinder 4 was very difficult to remove and looked rusty and dry (it had only been renewed 6 months ago). Compression test on this cyclinder (done cold) because I couldn't warm the engine up as a result of the oil pressure problem was low 120psi compared to 175 on cyclinders 1 and 2 and 163 on cylinder 3. I then put the new plugs in.

The engine started first time but immediately gave an "off the scale" oil pressure and before I could react blow the rubber gasket on the new oil filter and again filled the bilges with oil.

What can cause this degree of high oil pressure. I am thinking problems with cylinder 4 exhaust valve (perhaps caused by the original overheating problems) and now letting water in causing a milky brown oil and some how preventing the oil from flowing as it should. Is ther any tests I can now do to find the cause of the high oil pressure?

Many thanks