I was out on the boat last weekend and was cruisin

[stocky]

I was out on the boat last weekend and was cruising around for 1-1.5h at about 3500rpm. I then decided to increase throttle slightly to about 4200rpm when the motor all of a sudden had no guts and was idling really rough with the smell of smoke from unburnt fuel. I pulled the plugs and had 5 wet and 1 dry. I limped to shore and spent about 2h there, and then headed off for the ramp. The motor started 2nd kick ran rough for a few moments and then ran like a dream at about 4000rpm for the 30 minute run back to the ramp. I hate problems like this. Does anyone have any suggestions of what might be the problem. The motor is a 150hp Mariner 85-86 vintage. Thanking you all in advance. I have a feeling it maybe the unit that supplies voltage to the spark plugs and is breaking down when hot.

[squire]

stocky it sounds like your problem could be due to fact that you ran at low rpm for to long this carbons /wets the plugs or as they call it fouled plugs. It is a more common problem than you think. Hence when you came home at higher rpm it would have cleaned it out a bit. Try to run around the 4500 rpm. I dont think its your power pacK otherwise at 4000 rpm for 30 mins would have done the trick.Power packs usually play up when cold or cause the engine to snuff when throttle is opened up from idle. hope this helps regards squire. ps always carry spare spark plugs.

[stocky]

Thanks for the post Squire. I would not have expected the plugs to foul running at 3500rpm, but maybe at trolling speed. When I pulled the plugs I cleaned and dried them before putting them back in. The motor still had no guts and ran like a sick chook for a period of 15 min before beaching and having a two hour break. I was also surprised that when I pulled the plugs after running the motor for over 1h that I could hold them in my hand without burning.

[stocky]

I have gone through the diagnosis sequence from the manual and it appears the problem is a dud stator. To help others in this situation I will give my results. These measurements are made from wires to the switchbox.

Trigger test
Wires
Brown (no yellow sleeve) and White (with yellow sleeve 1351 ohms (to specification)

White (NYS) and Brown (WYS) 1245 ohms (TS)

White (NYS) and Violet (WYS) 1294 ohms (TS)

Trigger OK

Stator test

Red to ground 130 ohms (To Specification, TS)
Red/White to ground 130 ohms (TS)
Brown/White and Red/White 5700 ohms (TS)
Brown and Red 9000 ohms (Not to Spec.)

Stator stuffed.

Hope this info helps someone in the future.

I am new to Brisbane and I was wondering if anyone could recommend somewhere I could purchase a stator for this model Mariner.

[deb]

Stocky
we have a similar old mariner, try Downes Marine in Bowen Hills, they don't advertise doing merc's but they certainly have found the right parts for us over the years. ;)