Mariner 150 - High altitude, changed jets, no go!!!

[DocBob]

I recently moved from just above sea level to approximately 6000 feet. I have already changed the jets on my 150 and in neutral the engine runs like a champ. Idle and throttle up are great. As soon as I drop it into gear though it just dies. It's a quick death if I try to throttle up, or a slow death at idle speed.<br /><br />I'm not a mechaninc by any means so in asking around I was told I needed to change the timing advance. The manual seems to only give one setting. Any help/suggestions?<br /><br />Engine serial number: 06637205

 

[wilde1j]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Timing doesn't change with altitude ... something else is going on.

 

[LubeDude]

Re: Mariner 150 - High altitude, changed jets, no go!!!

you may have leaned it too much on the Idle side.

 

[stant1man]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Bob, the atmospheric pressure at that height is lower meaning that the air is not as dense. (Makes engine run rich)<br /><br />You should not amend your timing at all. The problem here is that your engine is now too rich, the excess unburned fuel is fouling your plugs and causing it to load up at idle. LubeDude got it right with mixture, but i believe its too rich. <br /><br />Solution is the same, screw in each idle needle, revs will pick up and then eventually stumble, at this point back it out half a turn. Do this on each carb then once you have your idle just nice, turn each needle out 1/4 of a turn. Then try your hole shot. If it still bogs turn needles out another 1/4 of a turn until your winning.<br /><br />Let us know how you get on...<br /><br />Stan

 

[wilde1j]

Re: Mariner 150 - High altitude, changed jets, no go!!!

I think idle and main jets are fixed and he said he rejetted for altitude. My 150's are all fixed jets.

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Thanks for the input...Stant1man is correct the engine is definetely running rich, I can smell the unburned fuel. Unfortunately, (quote from my Clymer manual) "carbs on this engine are not equipped with adjustment screws. All adjustments are made by changing the size of the fixed jets." <br />I consulted with the forum (My previous post) regarding the proper size and replaced all 12 jets (v-6 engine with 3 double barrel carbs #WH-29 ) and it does run great in nuetral...but nothing else.<br />It sounds like I may still not be jetted correctly. The jets I had on the Chesapeake Bay were:<br />Main Jet - .064<br />Idle Jet - .056<br />Vent Jet - None<br /><br />According to the chart, for operation at 6000 ft you would go to .060 for both idle and main jets. Mains .004 smaller than standard and idle .004 larger than standard. Merc part no is 1395-6487 for .060 jets.<br /><br />Does this sound about right, or do I need to try another set of jets???...This could get expensive!!!

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Actually, I was just thinking...sometimes that's not a good thing...but if the air is leaner up here, and the idle mixture is too rich...should I try putting the old (.004 smaller) idle jets back in to lean it out more, and see what happens, or am I thinking about this all wrong???<br /><br />And along that same line of thinking, what is the reason the the main jets get smaller but the idle jets gets bigger with altitude? Shouldn't they both get smaller? <br /><br />I'm so confused!!!!

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

WildeOne is correct, I did rejet for altitude.

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

OK, I've noticed that the vent jets should be reduced in size for alitude on most engines, but my engine has none. Therefore no recommendation was made for their size. Could this have anything to do with it? I'm pretty sure the threads for them are present, but none were installed from the factory. I don't know what effective size this makes the vents, but could installing jets there help?

 

[stant1man]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Bob, im confused now too. If you go to higher altitude you should be putting in smaller jets in both idle and main. Put the smallest jets you have in on both idle and main, see how you go and take it from there. <br /><br />If you have put a "richer" jet in the idle then I

 

[stant1man]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Bob, im confused now too. If you go to higher altitude you should be putting in smaller jets in both idle and main. Put the smallest jets you have in on both idle and main, see how you go and take it from there. <br /><br />If you have put a "richer" jet in the idle then I would expect it to load up and cut out for sure, I would also be expecting it to fall on its a$$ when you try to get out the hole. <br /><br />It would be running far far richer than it should be, i think your book might have a misprint.<br /><br />Stan

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Stan, you've hit it on the head. It does load up and cut out now, and forget about trying to get out of the hole...it dies even faster then.<br /><br />Unfotunately, in two full pages of carbs listed in the Clymer manual, my WH-29's were not even listed.<br />I got the jet sizes from a recommendation in my last post: High altitude jets for Mariner 150 .<br /><br />Quote:

Those are the sizes that were supposed to be originally installed for operation at 0 - 2500 ft elevation. According to the chart, for operation at 6000 ft you would go to .060 for both idle and main jets. Mains .004 smaller than standard and idle .004 larger than standard. Merc part no is 1395-6487 for .060 jets.<br />

Evidently that was not great advice. I'll try putting the old jets back in, but I assume I will need to go even smaller. I put in the .060 jets that were recommended, bad deal!!! I had .056 idle jets, which I will try putting back in, but I have a feeling that this wont work either since those did work fine at low altitude. Should I have actually gone down .004 to .052 idle jets instead of up?

 

[Coolmaker]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Dr Bob, call the nearest Mercury dealer and give him the serial # of your motor and the carb #'s. He can give you the correct jets. Be careful and do not run it long until you have them right, or you will fry a piston.....

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Good advice Cool, I will do that but was thinking a second opinion from someone with a little experience in this area might be a good idea as well.<br /><br />Thanks

 

[garyj]

Re: Mariner 150 - High altitude, changed jets, no go!!!

DrBob,<br /> My Seloc manual gives the same numbers as the correct jets for the WH-29's at 5000 to 7500 hundred feet. .060 for both main and idle. (no vent jets)<br /><br />The "main jet" (or high speed jet) controls fuel, therefore to reduce the jet size reduces the amount of fuel. Be careful when reducing fuel for high rpm's (lean condition - overheat -etc..)<br /><br />The "idle jet" controls air, therefore running a larger jet adds air thus causing it to run leaner at idle.<br /><br />First I suggest going back to the .064 for the main jets until the idle or bogging is corrected. (then you can monkey with the main jets after you get the hole shot corrected.<br /><br />If it is running too rich at idle, then you may need to increase the idle jets more. <br /><br />I would suggest to get some "numbered drills" (at you local hardware store) and drill the idle jets in increments until you reach the optimum performance at idle and out of the hole. (save money)<br /><br />Bits<br />Standard 1/16 = .0625<br />Number 52 =.0635<br />Number 51 =.0670<br />Number 50 =.0700<br />Number 49 =.0730<br />Number 48 =.0760<br />Standard 5/64 = .0781<br /><br />If it is running too lean at idle, then you may need to decrease the idle jet size (buy smaller jets). <br /><br />Good Luck<br />SC

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Thanks SC, that finally makes sense...smaller mains to decrease fuel = leaner mixture...larger idle jets to increase air also = leaner mixture.<br /><br />We're making some head way!<br /><br />I also like the idea of buying a few drill bits instead of more sets of Jets. I can certainly drill the jets out.<br /><br />OK, so I'll put the old .056 main jets back in to lean out the mixture...then try it out on the lake? <br /><br />Will this help with the idle thing at all, or will this still be a problem?<br /><br />Then if it runs better, I can start playing with the idle jet size? <br /><br />Or should I put the old mains back in AND start to open up the idle jets? Being a scientist we tend to resist changing more than one variable at a time...but if it gets me up and running sooner I can adapt!

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Wait, wait, wait...the old mains were .064 and the old idle jets were .056 . Both are now .060 acording to the Seloc manual (and by the way, I contacted Mercury directly and they did confirm these sizes).<br /><br />So now I should replace the new .060 mains with the old .056 idle jets to lean the mixture even more???...so have I lost anyone yet?!?! <br /><br />Or should I just try to open up the idle jets to start with?

 

[LubeDude]

Re: Mariner 150 - High altitude, changed jets, no go!!!

At this point, I think you are about right on the Mains, I would put the old Idle jets back in and see what happens. (You can do this without removing the carbs if you take your time), Being rich at Idle will only cause you to load up if you are going to troll a lot or have a long way to go through a no wake zone. It actually will smooth out the transition from Idle to full trottle. Now see if you can get out of the hole.

 

[DocBob]

Re: Mariner 150 - High altitude, changed jets, no go!!!

Won't the old idle jets, which are .056 (smaller than the new .060 idle jets) make the mixture even richer? Don't I want larger idle jets? Such as using the old .064 main jets as idle jets to increase air intake...I am bogging bad and seem to be running too rich already.<br /><br />According to previous posts, and the recommendations from Mercury, I need larger idle jets at altitude.

 

[LubeDude]

Re: Mariner 150 - High altitude, changed jets, no go!!!

First off, I dont think that the thread size is the same on the jets, (Idle and main). Can you get on plane eventually at all?<br /><br />Did you ever run the boat the way it was when you moved there?