Altitude Tuning/ Jet Size

R.Johnson · Jun 2, 2004

Re: Altitude Tuning/ Jet Size

kentt: Sorry I'm so late getting back to you. You need to run a 3/8 fuel hose on your engine. The chart I have lists the following jets for 6-10000 Ft. Low speed #29, high spped #52. The tool you made to remove the jets is correct, but this will be easier to use. Just take a phillips screw drive of the correct diameter, slightly smaller won't hurt, and grind it just like the tool you made. Hope this helps.

kntutt · Jun 2, 2004

Re: Altitude Tuning/ Jet Size

R.Johnson: Interesting. Your saying a 52 for the high speed and a 29 for the low. As you read I have a 32 for the low and a 59 for the high. I am trying a 54 as you know by reading this. I am still 3 jets short for the high speed and as you read the 32's have stripped screws on them. I am going to try the 54 first and see wha they do. Thanks for this information. I would guess that with the 32's switched to 29's it would start easier as it is probably flooding out. Where can I order jets on line, and how much are they now? Another mechanic today told me that they don't chenge the jets, just the timing. That makes no sense to me.

kntutt · Jun 2, 2004

Re: Altitude Tuning/ Jet Size

By the way, I tried NAPA today they spoke to me on the phone like I was nuts. They said they have no boat parts and don't know how to order any jets for this engine. I explained that I had heard that they could order them and they thought that any NAPA dealer that coudl order such parts must be region specifice such as Florida. The local (within 50 miles) boat shops say that they are special order. The next closest place is Grand Junction Co. to the west of me about 100 miles. See how much fun it is to live in the Rockies if your a boater!! Now if you need snow skiing equipment or hunting/back packing equipment well thats on every street corner.

ezeke · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Just as a follow up on the NAPA problem, you might want to read through this thread: NAPA thread

R.Johnson · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Kentt: Don't worry about using those #54 jet's, or the #32 low speed jet's. Here is what those numbers mean. A #54 jet has a .054 of an inch hole size, a #32 jet has a .032 of an inch hole size. If your engine is a 1978, the service manual state's that it came with a #58 high speed, and a #32 low. If you run a #54, it will be running slightly rich, and may not give peak performance, but if you are going to err, it is much better to err on the rich side, as running lean can damage an engine in a very short time. Running the wrong size jet on the low speed end will only give you a poor idle, or poor acceleration. The low speed jets are easy to get at, so you can experiment here. The jets you need will have to come from an OMC dealer, they should be no problem for them to order. Do not change the timing as someone suggested. When you get your engine up and running. Work with your engine set-up until you get it into the 5500 rpm range. This will mean engine height on the trasom, and possible propping. Again run that engine on a 3/8 fuel hose. Let me know further what you mean by saying that the #32's are stripped. Did you make the jet removal tool as I suggested?

kntutt · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

R.Johnson: Thanks for your response. I have not made any new tools as I am at a stand still until I get the new jets which I am still trying to find. I have friends in Lake Powell at the moment and am trying to reach them by cell phone to see if they can pick them up for me before they leave for home. The tool that I made worked well on the one side so if it works on the other I will keep it. If it does not work I'll use your suggestion. The engine that I have says a 1977 if you look at the last picture that I have up there of the starboard (I need to get the boating lingo down again) side fo the engine. The white piece that runs vertically up the side of the engine that has the yellow sticker on it says 1977 175 hp Johnson on it. I am going by that at the moment. Now to answer your question about the head stripped screws. If you look at the picture that I am referring to above you will see that there are two large pieces of linkage on each carb that that are connected together to the other carbs by rod linkage. The large piece of linkage closest to the rear of the engine or intake manifild has a screw just below and behind it. These screws cover the low speed jets (32's). It is these screws that have the heads stripped off of them so that a screww driver wont grab. And of course as you move towards the lower carbs they are more difficult to get to. It is easy to see the screw if you look for it on the top carb. I am trying to avoid taking the carbs off so will try the boat with just the high speed jets changed first, although it is difficult to start at 7800 feet.

kntutt · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Actually if you look at the top carb and the pin that the rear large piece of linkage is centered on, the low speed screw is just below that. You can barely see the next one on the second carb and the third one is hidden from view.

R.Johnson · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Kentt: I hope I'm following you here, the screw's that cover the low speed jets appear damaged, as do the high speed to some extent. One way you could remove them is with a hammer impact driver. This is a tool you can purchase at Sear's. With the tool get a 3/8 to 1/4 reducer. Buy a 10" long 1/4" extension, cut off the end, and grind to a screwdriver bit. This should shock those damaged screw's free. There is a gasket under these screw's, they should not have been put in this tight in the firsat place.

ezeke · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Do you want me to check here at my J/E dealer? I could mail them up to you. Might make it by Monday or Tuesday. Or you could call them: Nauset Marine in Orleans, MA 508-255-0777. Ask for the parts department.

87Aggie · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Going back to NAPA offering marine parts. The one I deal with has quite a large catalogue with pictures and everything dealing with different motor brands. I have a 78 Johnson 140 hp and they offer everything I've needed so far. If the "jets" are the same thing as needle and seat. I check here and see if they offer them.

kntutt · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Aggie: I was just at napa going through there book. The jets are different than needle and seat. I looked at there boat catalog and they don't seem to have them any jets. We have similar year engines. If anyone knows the catalog number for NAPA of a 54C jet for a 1977 Johnson. Please let me know. I can have them order if for me. Ezeke: I hate to put you out of your way. Maybe I will call them. I am still trying to get my neighbors who went to Powell for a week with there 94 23' Fourwinns Horizon. That is a sweet boat. Rjohnson: You are following me correctly. I do have a hammer impact driver and thought of that already. Remember I used to do this kind of thing as a kid. I was concerned because the last thing I want to do is hit the impact driver and break the carb body. The problem is they are stripped on one side. To start grinding them down and cutting slits for a new screw driver hold would mean I have to take off the carbs. The first thing I want to do is try his with the new high speed jets. Although, I don't think that this will address the problem of the engine not starting. That may be related to changing out those 32's. It looks as if I won't be able to try this boat this weekend because I can't locate the jets locally. That is ok I am in the middle of fixing up my house for an appraisal.

DJ · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Sorry to break in here. I've been following. Very educational. I just wanted to reiterate one thing that may have been overlooked. You need the 3/8" fuel line. The whole line, tank to engine. Also, it should be a big deal to ahve a few jets shipped to you. They are small and light. A dollar or two for shipping will cover any dealers shipping expense.

R.Johnson · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

The needle, and seat has nothing to do with jet size, jet's have to be ordered through an OMC dealer, NAPA won't have them, nore will they know what you are talking about. Simply tell the dealer you want a #54C high speed jet, they will have the current part number, and put them on order.Kennt: you got me laughing with that impact wrench! I used to be a kid!

kntutt · Jun 3, 2004

Re: Altitude Tuning/ Jet Size

Welcome DJ. I agree with both of you. I just got off the phone with my friends who got back from "the trip from hell" at Lake Powell. I have the name of a shop in Grand Junction and will have them ship me the jets tomorrow if they have them in stock. If not I'll order them. I was hoping to have them for the weekend, but they are not to be found within a 100 mile radius. I am simply at a stand still until I get these jets in. The fuel line on it now is a 5/16. I just bid on one at ebay to replace mine. If I don't win or it doesn't work I'll make one up using a 3/8 line. I am juggling boat repair, home repair for an appraisal for a refinance, and carb synching my motorcycle. R.Johnson: As a kid you have to have an impact wrench. You can't imagine what it was like trying to get those damn 650 Triumph motorcycles not to leak. Oh yea, every once in a awhile you had to take off those side covers to replace a gasket, and they had phillip head screws that were impact wrenched on. That was fun. No one had the extra money to put the allan head screws on. And, don't forget tighten everything down as tight as you can get it. Remember those days? It wasn't until later that I realized that a good mechanic has a torque wrench built into his arm!! Hell I am an old guy now (55). You know just a few years from drooling all over myself. I was a car nut for years. I still have my original 56 chevy hubcaps. Another great choice in life. My dad sells my car and doesn't tell me. Afterwards he hands me the hub caps, and.......believe it or not the $25.00 he got for the car. I had rebuilt the engine and the car was great. And, he wondered why I became a Shrink!! That's another story and that life is gone. The older I get the less I trust other people working on anything that I own. I just don't have the balls to do my own dentistry!!

kntutt · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

Just to give you and idea of how crazy it is to get parts it took me ten minutes on hold to reach the parts department in Grand junction and they can't even talk to me. That parts guy said that there are "35 people at the parts counter" and he took my order and will have to call me back with price and availablility. He didn't evne have time to take my credit card or shipping address. Isn't life wonderful!

kntutt · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

I called a second marina, where I got the first three jets years ago. They had to check. They called back and only had two jets and not three. I will wait for the original place to call me back and see how many they have. I may need to order from two different places or call the east or west coast to get all three at once.

kntutt · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

Grand Junction called back and told me that they do not have them in stock and it would probably be 2 weeks to get them in and then ship them to me. I would of course be responsible for shipping charges both to them and than to me. All this and I only have to wait 2 weeks. Let me see the boating season up here is good from about June,1- September, 1. Time to call the east or west coast.

kntutt · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

I found the f***ing jets!!!! They were in a little marine shop in Denver. They are are being shipped to me tomorrow. It only took 6 hours to trace them down.

R.Johnson · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

Kentt: When you get those jet's, make sure they are all Letter C, C & D look just alike externally, but Are bored differently internally. The are machined for opposite direction of fuel flow. I go along with your comment on home dentistry, you may need a little therapy by the time those carb's are done with you though.

kntutt · Jun 4, 2004

Re: Altitude Tuning/ Jet Size

I ordered 3 more 54C's so and told them that it was for a 77 Johson 175 horse. I assume that they should be the same as what I have already installed on the other side. I am assuming that they will be here by Tuesday or Wednesday. I made sure that I could loosen all of the float bowl screws to get to the jets on the side that I had't touched . I was able to do so. Even the difficult one on the bottom. I pulled out the top two jets and they were 59C's. I 'll take out the bottom one when the new ones arrive. I am just preparing for a smooth transition. Well I'll accept a semi smooth one any way. I also asked them to check to see if they have the low speed 29's that you recommend in stock in case I need them later. They said they would do so and put a note in the box when they send it out tommorow. What I want to do is figure a way to start this engine easily without flooding it out. I will not push in the choke the next time I try to start it and see if that makes a difference. If it is still difficult to start I will have to change out the low speed jets. I assume if I go to Lake Powell in the fall I'll have to change everything back. My friends, who just returned, said that the water level is very low there. The government is warning that this could be as bad a drought year for the west as 2002. That was the summer that we had all of the wild fires here. The worst in the stated history. As of now the rever water levels peaked in May. This usually happens in June. Not a good sign for potential wild fires. Ken

Altitude Tuning/ Jet Size

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