Fuel Bowl Vent Jets not present?!?!?

[DocBob]

I'm doing my first carb tear down and cleaning on my 1985 150 HP Mariner V6. I'm following the directions in my Clymer manual (Mariner Outboard Shop Manual 2-220 HP 1976-1989) and came across a problem.<br />Page 250 #10 (third paragraph) says "it is not necessary to remove the fuel bowl vent jets (B, fig 132) for cleaning purposes". The photo on page 251 figure 132 letter "B" shows the jets in question.<br />They are missing on my motor. The threads to accept the jets are there, but the holes are empty in all three carbs (all 6 jets). I can tell the carbs have been rebuilt in the past. Where these get left out on purpose? <br />I'm having problems with acceleration and am wondering if this could be the problem, or were these left out to actually enhance performance?<br />Should I replace them or leave them out?<br />Thanks in advance,<br />Bob

 

[mellowyellow]

Re: Fuel Bowl Vent Jets not present?!?!?

it worked without them 4 how long?<br />I would look more at the float/needle/seat...<br />good luck,<br />M.Y.

 

[DocBob]

Re: Fuel Bowl Vent Jets not present?!?!?

Thanks MellowYellow<br />Last summer was the first year I had the boat, and the problem was present the whole time. When I hit the throttle too quick, I kill the engine. The engine idles a little rough too, but I didn't want to tear it down during fishing season and it ran at "WOT" great. Getting there was the problem. Someone suggested that the carbs should be rebuilt because it sounded like the mixing chamber gasket might be leaking.<br />These jets lead directly into the mixing chambers...so I'm worried that it might be the problem???

 

[rodbolt]

Re: Fuel Bowl Vent Jets not present?!?!?

hello<br /> rebuild the fuel pump while your at it. merc v6's had a tendancy to stretch the diaphrams and the enine would idle fine but not keep the fuel bowls full and on hard acceleration they would stall. pump the primer after the stall and it would run great.<br /> for your jet problem. man merc made a half a million different variations of the same thing with nminor changes. try to access mercury parts express using your engine serial number then try to determiner if your carb model is supposed to have them. <br />good luck and keep posting

 

[DocBob]

Re: Fuel Bowl Vent Jets not present?!?!?

Thanks rodbolt. I had planned to rebuild the fuel pump too...I'm planning on working my way through the whole fuel system...even the fuel lines are a bit worn and those are getting replaced all the way back to the tank (includung adding an inline fuel filter and a new primer bulb. But it actually does sound like the fuel pump might be the more likely culprit. It will be interesting to see how it runs this summer.<br /><br />By the way, I did try to access the Mercury parts express site before posting here (for exactly that reason, I wanted to see if they were even listed for my carb) but the site is down rite now!!!

 

[DocBob]

Re: Fuel Bowl Vent Jets not present?!?!?

Hey Rodbolt, you nailed it with the fuel pump gasket. I hadn't planned to pull the pump yet because I haven't received the gaskets yet but since it was in the way for pulling the midddle carb, I did...and you were right, the diphragm was completely out of shape. That should make a big difference when I get that changed. THANKS!

 

[Mettaree]

Re: Fuel Bowl Vent Jets not present?!?!?

DrBob: Parts Express is back up.<br /><br />

 

[wingwipers256]

Re: Fuel Bowl Vent Jets not present?!?!?

what is the carb # it is stamped on the top of the carb usually a wh # some carbs had no vent <br />jet in them. give me the # and Ill look in the<br /> book <br /> Phil

 

[DocBob]

Re: Fuel Bowl Vent Jets not present?!?!?

Thanks all! Great help!<br /><br />Phil, The carb numbers are WH-29 (followed by #1,2 or 3 depending on which carb you are looking at).

 

[Clams Canino]

Re: Fuel Bowl Vent Jets not present?!?!?

The inline 6 guys routinely throw the bowl vent jets away to richen up the midrange and prevent burning up pistons. Perhaps the V6 is the same?<br /><br />-W

 

[rodbolt]

Re: Fuel Bowl Vent Jets not present?!?!?

hello<br /> you really need to pick up a factory service manual. they have a description of each jet and how it functions as well as what happens to the air/fuel mix if you go larger or smaller with the jet sizes.<br />it also explains where each jet is.<br /> it can be confusing if your not careful. some carbs only had jets in the stbd bores some had jets in 4 out of six locations and some used 5 jets and some used 6. I worked the merc thing for some years in the 80's and 90's all I can say is, wow they did a lot of funky jet things.<br />good luck and I hope no one has been tinkering. the back draft carb is about the least understood of all carbs. many a good engine was ruined cause the wrench had no clue.<br /> good luck and keep posting

 

[wingwipers256]

Re: Fuel Bowl Vent Jets not present?!?!?

DRBOB the books say the wh 29s have no<br /> vent jets.<br /><br /> Play Safe<br /> Phil