second time out with the 150, a little better

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Jofly

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Feb 1, 2010
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I went to cartes lake on Wed to mainly tes run the motor after new plugs and wires. I still have a few issues, While on plane @ 5200 RPM it instantly dropped to 3000rpm for about 30 seconds and then it went right back up to 5200. It only did this once. Wrenchin2 gave me Sam Jenkis # and last night I called him and he was thinking power pack for that problem, told me to check the terminal strips and the grounds first. So that is on the list of things to do. Second when it would run at high end it would chatter, the guy I was with suggested the leaf valves may be going bad, it's an 88 motor so I guess it could be possiable. Sam also told me to install a water filter seperator and run 93 octane in it since its a GT model. Any advice on the leaf valves? Do they go bad? I did buy a manual for the motor so i can figure out how to inspect them but it would be a pretty involved job. And last but not least SPEED!!! I have a 19' VIP, the motor is a 150 gt johnson with a 19 pitch prop(seems low to me) and the fastest I could get it to go is 40 mph by gps. Seems slow for a 150, but i dont know, my old 90hp would run 47 with a 19 pitch prop and it was a deep V. I just got a 10" jack plate, but I'm trying to wait till winter to install it since I have to pull the power head and install a new upper mount. Any thoughts and suggestions would be helpful emoToast.
 
Reeds will not cause it to loose power like that. Reeds will show more issues at idle and will be blowing fuel back out of the carb and will flood a cylinder. It floods because air passes the venturi twice and draws fuel out on each pass and will "double" the fuel amount.

The clatter may be it eating a piston. Need to do a compression and leak down test. Did any of the plugs have aluminum on them???? That GT is actually a around a 175HP engine. So it should do better than that. It may also be that you have a "PUSH" prop meant for a houseboat and not a bass boat as the characteristics don't lift the boat, thus doesn't perform.

AS far as 93 octane goes, that engine is designed to run on 87. Your engine is a low compression engine (85-95 PSI). You need to understand what a octane rating actually means. At lower compressions, the HIGHER the octane the SLOWER it burns and harder it is to ignite under lower compressions. That is why if you have a high compression engine, you run high octane fuel. The temperatures that high compression creates can ignite the fuel causing detonation "spark knock" with lower octane fuels. Your engine has 30* BTDC (before top dead center) of timing (i always set them to 26* for safety) . Meaning that the spark ignites the fuel .180 of a inch before the piston reaches the top. This allows the burning air/fuel to create the most "PRESSURE" and pushes the "HARDEST" on the piston as it passes TDC (top dead center) and starts downward. These are settings for the 87 octane. You run 93 octane and due to characteristics of the fuel and the low compression of your engine, the piston moves further ATDC (after top dead center) before the fuel creates the "HARDEST" push. So 93 octane will cause the engine to loose power and cost you more $$$$$. Two things can be done to make up for the slower burning rate of 93 octane. Increase timing to compensate for the lag in combustion or increase compression. Increasing compression will make the fuel more volital (burn faster and easier) and you will see a increase in power. But stock form, it is a waste of money. If you want to run Higher octane, run 89. Of course these are my opinions. emoToast emoToast
 
I did run a compression and leak test, I will post the results tonight when I get home. I also started going through all the electrical connections and cleaning them and all the grounds. I will test the spark rates and other stuff on my next days off. I got a water pressure guage as well. How do I tell if I have a PUSH prop?
 
The blades will be almost straight up and down on the rake. Did you do a leakage test at TDC or past? I do them at 1/2 ATDC because carbon will build at the top of the cylinder and act as a seal. Just my .02
 
I didint look at the tdc, I'll redo the test monday and pay attention to the position. The way I leak tested was just crank it and time it for ten minutes to see if the pressure dropped. There was no signifigant drops, Pressures were 78 to 85 on one plug at a time. And 85 to 88 with all plugs out.
 
Ok wrenchin2, heres how i did the first test. Took one plug out at a time, cranked 2-4 times and recorded pressure, waited 5 minutes and watched pressure again. These all stayed the same. and were starting facing toward the bow behind the motor on the port side top to bottom; 78#,85#,85#, starboard top to bottom; 80#,80#,80#. Next test take all plugs out and crank 2-4 times and record pressure and wait 10 min and record again. Same as above for the order;90/90#,90/90#,90/90#, starboard; 85/80#88/84#90/90#. So since I didnt do the TDC thing what do you think? Also you need to educate me on prop details. I'm going to try to add a pic of my prop with this post. I think the rake you are talking about is the angle of the prop blade at the far aft, is this correst? If so Mine is 90* to the hub. emoScratch
 

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I Just want to thank you for taking the time to answer my questions, what I am learning now I will be able to pass on to other boaters!!!
 
?????????? A leak down test is a special tool that has 2 gauges. The first gauge tells you how much air you are inducing into the cylinder and the other tells you how much it is holding.

What I do is remove the spark plugs and rotate with a screwdriver in the plug hole. When the piston reaches TDC (the highest travel), mark the screwdriver where the plug threads start. Remove and make a mark using tape that is about 1/2 above the original mark. Install the screwdriver back in and continue to rotate clockwise until the new mark is flush with the threads. I use a pair of vice grips on the flywheel ring gear pushing against the starter to hold the engine. I induce 100 PSI into the cylinder and note the leakage. Do this to all 6. I do it this way because a cylinder will get a ring of carbon built up at the top of the cylinder and will test good at TDC but fail at 1/2". If it is a good cylinder, it will pass anywhere prior to the exhaust port or idle relief. I have had cylinders fail just to test them at TDC to have them to pass.

Here is a good example http://www.chattanoogafishingforum....4&highlight=150&highlightmode=1&action=search

I just got done with a 87 EVINRUDE 150XP tonight that I had to build because the compression was good but had high leakage. All failed the leakage test which is less than 10%. I Found #1 had 70% leakage. This means it was only holding 30 PSI out of 100 PSI being induced. When I tore it down, I found all cylinders were egg shaped and 3 pistons had the 2nd rings stuck on them from carbon. It was in such bad shape I had to bore all .020 to repair the out of round and taper that it had. This is unusual as I have .003 tolerance to work with and a high dollar hone that will keep a cylinder to within .0005 from side to side and top to bottom. That is 1/2 of a thousandths. I can normally repair a "out-of-round" cylinder and still be within limits without boring.

Here is a page out of a factory OMC (Johnson/Evinrude) manual. Read the whole page. Note it states IF the compression is good but operates poorly Check for........ This is telling you a engine with even compression can STILL have mechanical issues. A leakage test can determine this. I have found many problem engines that other places have said were mechanically sound because the believe only in a compression test. The one I got done with tonight, the guy paid to have it checked out and it was gave it a clean bill of health. Guy took it out twice and had issues both times and the guy blamed it on old gas, but was more to it.
 

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The prop looks to have very little rake. This will effect how it raises the bow. Do I see transom wedges between the engine and transom?????? If so this will change the effective trim angle that you can get. Meaning at full trim with the wedges is about the same as 1/4 trim without the wedges. This will hurt you due to the fact you can't lift the bow. Combined with the prop may answer your slow speeds. The plate on the back kinda scares me also. If the transom is weak, it can be flexing causing issues with trim angles as well.

I have a good friend that had a 18' Ranger with a 150 johnson on it. It was a slug with a 21P michigan wheel prop on it. It GPS 43 MPH at 4600 RPM. All we done was put a 24P raker I had on it and the RPMs went to 5400 and the speed went to 53 GPS even though it was a bigger pitched prop. This was because the prop could lift the boat. This is what you are doing when you trim a boat. The prop just couldn't lift it and the whole boat was being pushed through the water. I built him a modified mercury and when we went to the lake to "dial" it in, we tried 7 different props on it. There was a 8MPH difference between the fastest and slowest prop. This was with each one tweaked(all day testing). So a prop can make a BIG difference in performance. Just my .02
 
Got ya on the leak test. I'll try to find one, any place in Chatt sell them? As far as the wedges, yes and they are causing very negitave effects in my opinon. They will be removed. When I trim it all the way down it looks like it will become a submarine!!! I agree on the prop I will sort that out later, i'll make sure the engine is good first. The transom however seems very soild both inside and out. Once I get a leak tester I will post the results for you to ponder over. May be a day or two but you will here back from me. Your probably getting tired of me already and I have a feeling this is just starting. If the results are very bad is it all right to give you a call during normal business hours? emoToast
 
There are only 2 that I suggest you buy. That is a OTC 5609 or a Mac CDL210M. I have 4 of them. The only one I use is the OTC. The other 3 work but only use around 35 PSI of air and are not as easy to read. I bought them because they were suppose to be like the OTC. Two of them have been used only 1 time. If I am putting in 100 PSI and it is holding 70 PSI that is 30%. The PSI is closer to what compression the engine has and easier to determine percentage. Just my .02.

I will make you a GREAT deal on one of the other ones!!!!LOL!!!! emoToast
 
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