What carbs do I have

[jumbofordman]

I have a 89 Mercury 150 (ser# between C100861-C239552,) it was sitting up for 3 years when I bought the boat. It's on a 86 Checkmate Predictor 17'.

I'm gradually getting it running correctly, but it's running really rich at idle. So rich, in fact, that it won't idle unless you give it a little throttle, and with the control I have, it's difficult to get it into gear (you have to move the throttle back and then quickly into forward.) Makes docking fun, too.

I've run a compression test, getting between 118-122 in all cylinders. The PO to the PO fiddled with things a bit, and I'm suspicious that he changed the jets, so I'm trying to determine if I have the right idle jets in there.

Right now it has .046 idle jets and .074 main jets.

The numbers stamped on the carb (from block flange outwards) are:
1274-5427-0 WH
157-
155
41-11458

Supposedly I'm looking for a couple of digits after the WH, but it's blank on all three carbs. I have already taken the carbs apart, cleaned them, reset the floats, put them back together with new gaskets. I fix older trucks and Jeeps, so I do have some carb rebuilding experience.

 

[darylb]

...

 

[j_martin]

Re: What carbs do I have

I think they're WH41 carbs. 41 idle is .052, and 41A is .048, which would be leaner. .046 would be leaner yet.

I suspect the link and sync is all fouled up, so idle timing is way slow. Setup on these is the carb buterflies are totally closed at idle. Idle speed is set by timing. Float level, needle valve condition, etc is critical. Don't even open them up without a gasket kit. If the bowl center gasket is not renewed, you can bet on them running sloppy wet at idle.

Throw gasket kits in the carbs, being real fussy on clean and adjustments. Then do a link n sync. Bet it'll be just fine. Might dog on takeoff which would mean you should put in smaller (stock) idle jets.

One thing shade tree mechanics don't understand about these engines is that all adjustments affect all other adjustments. You need to do the adjustments in the proper sequence as each adjustment depends on the previous adjustments being correct.

hope it helps
John

 

[jumbofordman]

Re: What carbs do I have

Correct me if I'm wrong, but aren't the idle jets backwards from the main jets in that a bigger number actually leans out the mixture?

I did most of what you said already, I took apart the carbs and used new gaskets to put them back together. When I did so, 2 of the floats were badly out of whack, one would never let the needle open and one would never let the needle shut.

A link n sync is probably a good idea, and I know I have a couple of bad spark plug wires (when I tested them the resistance went all over the place by just moving them a little,) I'm waiting for them to arrive tomorrow.

 

[Faztbullet]

Re: What carbs do I have

Correct me if I'm wrong, but aren't the idle jets backwards from the main jets in that a bigger number actually leans out the mixture?

You are correct.....

 

[j_martin]

Re: What carbs do I have

I stand corrected.

Still think main problem is tinkering with the carbs without renewing the gaskets.

 

[jumbofordman]

Re: What carbs do I have

I've mentioned in both of my posts that I used new gaskets when I rebuilt the carbs. Thank you for your help, though. I'll see how she runs this weekend once I get the new plug wires and I do the link and sync. If still too rich an idle I'll see about swapping those idle jets for some larger ones.