Help with finding jetting specs for high altitude

[Captain Fishfry]

Hello ladies and gentlemen,

Wondering if you could possibly help me in finding some information about jetting for a Mercury 150hp, 6 cyl. 2-stroke. S/N 0G605507. I have the SELOC manual, and it provides zero reference about jetting at high altitude, or specifically, the size and which jets to replace.

I talked with the techs at Mercury, and they told me to buy the tech service manual, so I called Mercury Publications, and they told me that their book will not provide me jetting sizes either, and referred me to the manufacturer of the carb itself for help.

This just seems like way, way more trouble than what is normally required for a relatively simple procedure. Even better, if anyone has an OEM tech service manual, can you confirm whether it does or does not have a jetting chart for elevation? Hopefully the tech I spoke with just wasn't on his game that day, but I don't want to spend $99 for nothing.

Any help would be appreciated, thank you!

(operating at 300' currently, need jetting for 5500')

 

[Texasmark]

Re: Help with finding jetting specs for high altitude

Merc used to use Tillotson (spelling?) carbs. Maybe still do. My OEM manual for a 90 hp shows jet size as a function of carb model number for all the engines covered my my manual....90 thru 125 hp, 3 and 4 cylinder. Nothing about altitude. You might try a Seloc manual, look at the top right of this forum in the heading. I bought use rights to one (just go online and pull off what I want without having to pay for the whole thing) and found that they are a much more thorough manual than my OEM.

Mark

 

[Captain Fishfry]

Re: Help with finding jetting specs for high altitude

Right, I have the Seloc manual, but the only thing it has on the main jets for my engine is simply a note with an arrow pointing to "main jet". I've flipped back and forth from cover to cover of the manual and I can't find a thing other than general carb maintenance. That's why I was hoping Mercury themselves could/would help. The problem is, I only need a starting point, such as the stock jets at 0' elevation, from there I can figure out basically what jet size I need. I'm just really surprised at Mercury's lack of assistance.

 

[Texasmark]

Re: Help with finding jetting specs for high altitude

Right, I have the Seloc manual, but the only thing it has on the main jets for my engine is simply a note with an arrow pointing to "main jet". I've flipped back and forth from cover to cover of the manual and I can't find a thing other than general carb maintenance. That's why I was hoping Mercury themselves could/would help. The problem is, I only need a starting point, such as the stock jets at 0' elevation, from there I can figure out basically what jet size I need. I'm just really surprised at Mercury's lack of assistance.

Ping the following guys and one of them can at least get you the stock jet size: Steelspike, Silvertip, CharlieB, and/or Chris1956. Surely more out there but these guys I know can help.

Mark

 

[Chris1956]

Re: Help with finding jetting specs for high altitude

Fishfry, The serial number puts that motor at 1996? I looked up the altitude jet changes for someone else for a 1998 Merc 150HPV6. My Clymer manual only goes up to 1997, but it is likely the same, and this manual has been accurate, except for some obvious typographical errors.

The 1997 Merc 150HPV6 shows a WMV-2 carb all main jets of 0.074. It recommends jet size 0.070 for altitudes up to 5000ft, and 0.068 for altitudes 5K-7000feet.

Your 1996 likely has a WMV-1 Carb. You should look at the jet size and reduce it by .004 for 5k eleveation and .006 for 7K elevation.

You probably do not have backdraft jets, so only changes to the main jets are necessady. Idle mixture adjustment may also be necessary.

 

[Captain Fishfry]

Re: Help with finding jetting specs for high altitude

Chris, (my name as well)

Thank you very, very much. This helps me tremendously. I'm still going to try and find some publicated info for my own benefit, but you definitely have me going in the right direction. The jets that are in there now are .074. The plate on the engine is stamped 1998 under the serial #, so not sure what's up there.