what's the brown & white wire?!

DonMacN · 19 October 2008, 18:08

Folks,

Pretty new to this forum - grateful for any help.

I have a 90hp Mariner (1994 vintage). I've been having running problems, of which more later, but when I picked it up from a dyno test a few weeks ago the trim switch on the engine itself wouldn't work downwards. It would work 'up' OK. So bought a new switch, but found it was just the same. Seems the guys had mis-connected the switch wiring. I had a wee think and got it to work just fine by connecting blue/white to blue/white and green/white to green/white (pretty obvious). However I've been left with two wires coming out of the 'loom'. One is brown with white stripe and a 'male' connector, the other is tan or beige with a 'female' connector. I could connect them together, but don't understand why they'd be rigged to run the length of the boat just to connect under the engine cowl. Anyone able to tell me what these are for, or point me to where I could find a wiring diagram for this motor? Ta.

On the bigger picture, the engine has been dropping power. Sounds like a pot has been dropped, then when revs reduced it will surge back in again. On one occasion it was dropping at exactly 4400rpm then able to come back up once revs dropped to 3200, would build to 4400 then drop again. Could repeat that 4400 - 3200 pattern regularly on that occasion. Since then it's been more intermittent, but last time I was out it was pretty much more 'off' than 'on'. No fun when heading into the Pentland Firth with 4 divers aboard. I believe these engines had a stator problem, but this one has had the 'red' stator fitted. I thought it might be the oil feed pipe, perhaps a bit sludgy, but took the bottle off today and there was no problem with that. Engine might be old-ish, but reckon it's only done about 250 hours. On the dyno the guys in the shop reckoned it was pulling very well and producing good power, but they were unable to replicate the fault. Any suggestions?

Many thanks

Donald

Poly · 19 October 2008, 18:48

I think you are describing the same wiring as Dino here:

http://rib.net/forum/showthread.php?...light=tan+wire

As for the engine problem - if it happens on the boat and not in the workshop I would suspect fuel starvation? but am sure someone more knowledgable will be able to comment.

DonMacN · 19 October 2008, 21:49

Polwart,

Thanks for that - does sound as if I can relax about the wires. I have no trim guage, so the brown/white will be redundant. I'd have thought the tan - temperature warning one could be important, but if it's a mariner thing to have these two wires there I'll let it be.

Ref the fuel starvation, I wondered about fuel issues myself and the day after I had the 4400-3200 run I took it back out again with a completely separate fuel system. Normally I run from a 70l inboard tank, but for this one I used a 20litre 'spare' tank on the deck with an entirely new fuel line/primer bulb/connector and it made no difference.

Might also be worth mentioning, when I was flushing it through at home after last time out I tried taking the HT leads off one at a time to see if that changed the quality of the idling noise. It made no difference. No matter which lead was off the idle sounded exactly the same. Have also had the continuity of the HT leads checked, so don't think it's that.

Still grateful for any suggestions.

Cheers

D

Turbodiesel · 28 October 2008, 13:09

Have you tried priming the fuel line primer when the problem happens, that way you can make sure the diaphragm pump is working. If it revs beck up you will need to overhaul the pump, you can get a diaphragm kit for it. Worth a try!!