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Author Topic:   Mercury 150 1994: Hard to start, bogs down at acceleration and dies
jemesiz posted 04-15-2012 08:06 PM ET (US)   Profile for jemesiz   Send Email to jemesiz  
Hi readers--my 1994 Mercury 150-HP has started to give me grief. I was out fishing and she died on me when trolling at idle, then just would not start at all--luckily my Trophy has twin motor. Checked the wiring: all good. Had spark and I even squirted some fuel into the carburetors; the primer bulb was OK, [but] no start. I could feel vacuu on front of carburetorss. Later, [the 1994 Mercury 150-HP outboard engine] started up when I had no choke and full throttle. Only thing, when I pull the throttle back to idle, she dies, and, if I rev her up and quickly accelerate, she bogs down and dies straight away, too. Maybe it's the spark advance module

I don't think it's water in the fuel as I use a separating filter and the other engine is OK.

Also, [the 1994 Mercury 150-HP] has recently started to overheat during mid range cruising. I have check poppet and thermostats. The tell tale is strong. I think [the cause of the overheat] may be a waterpump housing leaking or water tube leak where it connects to block. Or timing is out Any ideas?--Jeremy

jemesiz posted 04-17-2012 06:53 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Back again. I did a compression test when I got home from work yesterday and all was good at 120-PSI. Then I checked the Port side bank for spark: all good. Then the Starboard sideL all dead! No spark.

Will be borrowing a DVA from a mate who's a sparky so I can see if it's a dead switch box or stator. I think it wil be the switch box because the oil alarm module has been intermittently going off. I have already checked the oil pump, tank float, pump sensor and they all seemed OK plus I had replaced the alarm module several times with no luck. Will let you all know how I go.

jimh posted 04-17-2012 08:37 PM ET (US)     Profile for jimh  Send Email to jimh     
No spark--first thing to check with an in-line spark tester. I think those Mercury electrical components were made in Mexico. I remember a conversation I had with a fellow who ran a television repair business in South America. He told me, "When I see a set that says 'Made in Mexico,' I know I have problems."
outragesteve posted 04-17-2012 09:05 PM ET (US)     Profile for outragesteve  Send Email to outragesteve     
Sounds like a switch box. You can swap the two boxes and see if that isolates the bad box. Probably not the stator: You would loose spark on all 6 plugs either high speed or low speed. The trigger circuit controls one cylinder on one side, and 2 on the other. The other circuit controls the other 2 on one side and 1 on the other. (All on one side out is usually not the trigger) Also check all trhe grounds. What is your serial #? I may have a new switch box! Good luck
jemesiz posted 04-22-2012 10:51 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Thanks outragesteve but I have worse news...

I had a good go at testing everything yesterday with the DVA meter (set on AC) and now I'm only getting 23-24V from the HS and LS stator leads for both switch boxes (plugs out and cranking at 500rmp +/-).

Looks like the stator was on it's last legs.
It's a bit strange though... I looked up my engine model # (OG110...) and she should be a 40 amp stator. Well, I tested with my multi meter both HS & LS stators - and the readings look OK.
LS - 3800 ohms
HS - 105 ohms

May be a loose magnet on the flywheel?
Rectifier off charge stator affecting ignition stators??

phatwhaler posted 04-22-2012 10:54 PM ET (US)     Profile for phatwhaler  Send Email to phatwhaler     
That motor is a 40 amp however it's divided into two 20 amps circuits.

I would call CDI/Rapair for your parts and expert technical assistance.

jemesiz posted 04-23-2012 02:25 AM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Is the stator that charges the battery incorporated into each 20amp circuit?

I'll write them an email... I'm in Sydney Australia.

By the way... the CDI website is very usefull. That is where I found the measurement data for when I was teting the engine.

phatwhaler posted 04-23-2012 11:47 PM ET (US)     Profile for phatwhaler  Send Email to phatwhaler     
As. Far as I know the stator is divided into two 20 amp circuits with a separate regulator for each circuit. Usually the dc side of the regulator goes back to the hot side of the starter solenoid. Im not real up to speed on the relationship between the stator, trigger, and switch boxes. You might want to chime in on for the real Merc gear heads.

By the way my dad used to live in Forster, NSW. He'll get a kick out of me corresponding with a dude from Oz.

jemesiz posted 04-25-2012 06:49 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Thanks phatwhaler.

I love Forster... I go up there with the family every summer holiday. I always take my tinny with me and go out for a fish on the river.

I've emailed CDI for some advice and still waiting for a reply... will post their response.

Also, I've contacted a seller on ebay in the US for a price on a 40amp stator and 2 switch boxes. $300 including postage... not too bad.

Today I'll disconnect the rectifier and test stator output again. Should I have the DVA set on AC? Not sure of it's brand... is not a FLUKE.

I usually buy my outboard parts from the US... too expensive over here.

jemesiz posted 05-15-2012 03:30 AM ET (US)     Profile for jemesiz  Send Email to jemesiz     
G'day Guys,

yippee... my 40amp stator and 2 switch boxes just arrived today from the US! Second hand (fingers crossed it's OK)but I saved myself $700.

My original stator was P/N 3989610A24 and the new one is 3989610A17. I cross referenced it and they should be ok. I thought if I'm going to replace the stator I may as well buy the matching switch boxes too.

I'll try and put the new gear on over the weekend and take her out for a spin. Will update as soon as I get back.

gusgus posted 05-16-2012 06:11 AM ET (US)     Profile for gusgus  Send Email to gusgus     
I sure hope these items are the fix, but (stepping out on a limb here) I think it is fuel starvation. Caused by an airleak, a restriction or bad fuel. But it sounds to me like a fuel issue. Not electrical. But I guess we shall see soon enough. Bet of luck, I sure hope you are right.
jemesiz posted 05-21-2012 03:27 AM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Hi gusgus,

thanks for offering your help but I fixed it :)

I installed the replacement stator and switch boxes and she fired staright up and idled well.

Had no time to get the boat on the water but will try on Wednesday.

Will let you all know.

I have also replaced the water pump impeller and run a new bead of silican along the top edge between the ehaust tube and water pump housing section. Hopfully this will fix the overheating issue at mid range.

jemesiz posted 05-23-2012 10:56 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Took out the boat yesterday and the motor ran perfectly.

Started first go and ran smooth right out to 5800rpm. Even the temp was great never went over 160.

NOW... here is the bad news. The starboard engine is playing up!!! I noticed she was running a bit warm (just under 200 at 1200rmp & went up to 240 at 4000rmp) and the oil alarm went off sporadically. These are all the same symptoms that the port engine had previously. Then she started running like crap with no power over 2000rpm.

It looks like I may have cooked the stator for the starboard engine. It couldn't be bad fuel as both engines share the same filter/tank. I knew I should have replaced the water pump impellor... ran out of time last weekend so I only replaced the port side impellor.

Will test stator with DVA meter on the weekend. At cranking speed it should be:
140V+ on LS coil- blue or blue/white to ground.
20V+ on HS coil- red or red/white to ground.

Any one have a spare 40 amp stator for sale??

jimh posted 05-23-2012 11:13 PM ET (US)     Profile for jimh  Send Email to jimh     
Let me ask you a very important question:

By some chance, are your twin engines connected to a common battery? That is, are both engines wired in parallel with one or two batteries?

jemesiz posted 05-24-2012 10:50 AM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Separate single battery for each engine. As usual the negative battery posts have a cable connecting them. Standard Bayliner Trophy set up(as per designers wiring diagram).

I think I remember my electrical principal studies... equipotential bonding??

What are your thoughts?

I checked the stator output at cranking speed this afternoon(still connected to switch boxes). 22-24V LS, 16-17V HS... no good.

jemesiz posted 05-24-2012 07:58 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Disconnected rectifier and spark advance module... still no good.
Tom W Clark posted 05-25-2012 09:40 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
Switch box, not stator. Very common problem on those motors. Swap the module(s) from the good motor to the bad and see it that solves the problem.
jemesiz posted 05-27-2012 06:57 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Well diagnosed Tom W Clark.

I just logged in and saw your comments and can agree... I had one good spare switch box left over from when repairing the port engine. I replaced the switch box the was giving no spark and I got my spark back and she fire straight up!

I also suspect the the stator on the port engine was ok... just the bad switch box. Anyone know the correct resistance readings I should see for a "Mercury" (not CDI) stator?

Have replaced the alarm module too... it must have been damaged from the bad switch box.

Will take her out on the weekend and report back.

BTW. My spare alarm module would not beep. Fixed... had a high resistance on the earth wire. So if you have one doing the same, check the earthing connection is clean!

jemesiz posted 06-03-2012 06:44 PM ET (US)     Profile for jemesiz  Send Email to jemesiz     
Took her out on Saturday(bucketing down rain!) and both engines ran well. They started first time, both reved to 5800rpm at WOT and and no overheating.

Only problem was the oil alarm module went off. It was one I had previously used that was intermitently going off so I think I need to find a new one. Confirmed oil was pumping. May even be a funny switch box??

Thanks for all your comments guys!

Jkcam posted 06-13-2012 06:08 PM ET (US)     Profile for Jkcam    
Smooth sailing.

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