Need extra throttle to start 96 Merc 150 EFI

[markb]

1996 150 EFI. ser#OG351951. The motor requires extra throttle to start, then runs rough at idle and dies unless I put it in gear and give enough throttle to run. It was doing this along with not charging and radical tach reading . Yellow wires coming from regulator were burnt at connections. I replaced one of the regulators and it corrected the charging and radical tach issues and for the first few starts, the idle problem. After a few starts of motor, it needs extra throttle again. Recently replaced the ECU with one from Brucato. I don't know if voltage regulator has anything to do with the starting problem. Wondering if I should replace the second regulator since motor is charging 13 to 14 volts and tach reads normal now. Compression is 115 on all 6 cyl. new plugs, cleaned the filter for the fuel pump in the vapor tank, new water separation filter, new bulb, checked pick up tube in tank for restrictions. Could this be a dirty injector or one that's not getting current at low speed? Spark has been recently checked by mechanic but not since this starting/idle issue. Any ideas?

[markb]

Any suggestions? I don't know where to go from here. Where can I buy a service manual? Digital preferred?

[leonreno]

It has been recommended to replace regulators in pairs. You can’t get a service manual in digital form that is a legal copy, only paper copies sold by Mercury from any dealer, European Marine on here sells them, links in his signature.

[EuropeanAM]

+1... Those regulators needed to be OEM Mercury/Quicksilver, replaced as a PAIR, and any darkened, browned, burnt or melted bullet connectors REPLACED (especially on the yellow Stator Leads and the RED leads).

Have you checked the fuel pressure, and performed a complete Sync-n-Link procedure?

Engine still have an idle stabilizer/advance module on it?

[markb]

Thanks for answering. I have ordered the 2nd regulator. they are sierra brand. The yellow connectors on both regulators were burnt and apparently shorting together. Is the heat produced to do this because of something faulty or possibly a loose connection? Fuel pressure and synk-n-link were checked by mechanic previously, but not since this current problem. I am not sure what a idle stabilizer/advance module is. Where would i find this? If the 2nd regulator does not fix this I plan to have injectors cleaned. Any suggestions?

[leonreno]

I prefer OEM when it comes to electric parts but hopefully the Sierra brand will be fine, maybe the better of the aftermarket stuff. But you also need to make sure you are using wet cell, non-maintenance free battery. No AGM or lithium batteries or maintenance free batteries.

[EuropeanAM]

99% of regulator problems in these engines can be traced back to a battery or connection problem with the battery cables.

Especially where the yellow or red wires are showing signs of "crispy-smokehouse-syndrome".

[markb]

I have replaced both regulators and removed and cleaned every ground wire that I can find. Battery is fully charged and specific gravity is within range. Boat steers and idles fine on the first start. After running awhile (warm engine), the next start requires advancing throttle to start. The rest of the day it will not start unless extra throttle is used. When put into neutral, engine does. You mentioned idle stabilizer/advance module. Does it sound like this could be the problem?

[JOE54]

sounds like fuel leak in housing or flooding injector to me fuel psi test will tell ya if leaking off as suggested above , timming light will tell if modules are working properly

[markb]

How do I check the idle stabilizer? I have seen posts where idle stabilizer was removed. Is this a good idea or should it be replaced. If it can be removed, where would I get info on what to do with wires that would be left unconnected?

[JOE54]

timming light ,,,,some engines yes it is , WHERE right here , youll be removing wires

[markb]

Thanks for the reply, I’ll check timing. I assume that I need to back into lake on trailer rather than the muffs.?

[JOE54]

yes do not rev in gear on hose

[markb]

Still need Help. In addition to 2 new regulators (Sierra brand), I put a used idle stabilizer on. Same thing, first start at the lake is fine, idles and does not die. After going to fishing spot and fishing for 30 minutes, motor will not start without extra throttle. It will not idle in neutral either. I can run it at home with muffs till warm, then turn it off, then restart it just fine. Could this be temperature related since it works fine on first start but will not idle after running at lake? getting frustrated, about to pull my last hair out. Thanks for any help.

[JOE54]

yes it could be loosing spark when engine is used and components are heated