1983 mercury blackmax 150 missing

**Larryyota** · 08-11-2020, 09:42 PM

I have a mercury blackmax150 on a 1984 Glastron that I bought a couple months ago. Serial# 6414663
First off the original owner said it hadn't been run in 5 years. Im running premixed Pennzoil premium marine 2 cycle 50-1 gas, brand new 6 gallon tank and lines clamped with metal clamps. This is the first boat engine I have ever messed with and it seems like this thing had/has multiple issues

Took carbs off cleaned thoroughly and rebuilt. Replaced both switch boxes, new plugs and wires, rebuilt fuel pump replaced all gas lines and new 6 gallon tank. Compression checks good. Decarbed twice first time a good amount came out second time hardly anything. At idle the engine runs fine for a minute then will miss/flood for a few seconds and clear back up.
I have checked all wires found a set of the trigger wires corroded In two and fixed them. I have a new trigger but I don't think it's the problem I feel like it might be a problem with the stator. When I rebuilt the carbs I set floats flush with bowl. Also the engine had no thermostats. Before I installed the engine ran steady rpms but smoked bad like flooding. Installed new 143 degree stats today and engine runs better other than the miss.
Wot runs around 5200 rpm and ran great but haven't tested in water since stats. Only seen a problem Idle and low rpms. Any help is appreciated thanks.

**Merc 2.5** · 08-12-2020, 05:45 AM

Recheck pulse pump, if it ruptures the diaphragm it will flood 1 cyl, put a timing lite on each plug wire Make sure it will lite the light. What kinda parts did u use when u replaced stuff ? If u bought Chinese boxes. Good chance 1 was bad out of the box

**Larryyota** · 08-12-2020, 06:43 AM

I don’t have a timing light yet I will try to get one today. I used quicksilver parts and the old diaphragm looked good when removed now there’s a new one. It seems like when I pull the plugs number 4 seems to look more burnt than the rest

**Larryyota** · 08-12-2020, 07:34 AM

Forgot to mention all wires spark to plugs when I pull them off, but some have no change in engine tone at all like it’s not firing through plug.

**nitro_rat** · 08-12-2020, 09:55 AM

don't pull the wires off when it's running to check spark. if the spark can't get to ground it will fry the switch boxes. use a timing light or inline spark checker. Also you need to ground the kill wire (black with yellow stripe) when you're doing compression checks and stuff with the plugs out to protect the switch boxes.

**Larryyota** · 08-12-2020, 12:00 PM

Would a timing light from harbor freight work good enough

**keefallan** · 08-12-2020, 02:15 PM

Maybe.....maybe not............the usual crap shoot with harbor freight. Do you have a meter? you should get one. It will help you trouble shoot things in the electrical dept.

Read resistances on the the plug wires to start. The manual will also give you readings to check for ...for individual parts. The thing with troubleshooting is that you need to verify 100 percent that part "x" is working properly.........or you cant move to the next one. Some times we all get lucky, and others.........long drawn out process to find that little bugger.

**Merc 2.5** · 08-12-2020, 02:20 PM

Is the fuel pump mounted on outside of the #4 cyl? Isn't that where its gets its pulse? If its mounted on starboard side disregard. When u idle on hose do u see or smell fuel coming out of the prop?

**nitro_rat** · 08-12-2020, 03:22 PM

Originally Posted by Larryyota

Would a timing light from harbor freight work good enough

I think they only have a dial back light. I don't trust cheap dial back lights. try to find an old cheap unit that isn't adjustable, they're not smart enough to lie to you. i zip tie the trigger down so it flashes all the time. if you need another project you can get plans to build your own...

**Larryyota** · 08-12-2020, 04:51 PM

We’ll harbor freight didn’t have one I got a digital innova timing light from oriellys don’t know how it works I’ll try using it if it has instructions and report back. And I have a few meters but not sure what numbers or how I to test everything I don’t have a manual have to wait on that had to pay 110$ for a plastic timing light

**Merc 2.5** · 08-12-2020, 05:51 PM

Originally Posted by Larryyota

We’ll harbor freight didn’t have one I got a digital innova timing light from oriellys don’t know how it works I’ll try using it if it has instructions and report back. And I have a few meters but not sure what numbers or how I to test everything I don’t have a manual have to wait on that had to pay 110$ for a plastic timing light

Man I hear that bout timing lite. But those digital lights could and can give false readings on these things. I really hope it works for you. If u start seeing double flash could b the light. I've seen others with that issue

**Larryyota** · 08-12-2020, 07:42 PM

There's gummy looking buggers coming from exhaust and I won't able to check timing I got home late and my neighbors dont like the noise after dark. The fuel pump is in starboard side in line with cylinder 3 I think. It's near the poppet valve

**Larryyota** · 08-12-2020, 07:44 PM

Where can I get a good book for this motor? I don't know how to test any of these components without it I've tried finding info online but nothing.

**nitro_rat** · 08-12-2020, 08:21 PM

go to cdielectronics.com and download their free troubleshooting guide. You'll need a DVA adapter for your multimeter to do some of the tests. You can get a meter and DVA adapter on ebay for about $40. Also check ebay for manuals. you want the merc factory service manual. the one that covers 1983 is the thinnest, simplest one...