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Yamaha - after 27 year nap...with VIDEOS
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Recently I was having some performance issues cropping up with my old Yamaha 225 hp 2 stroke outboard. It is a 1988 and we bought it brand new 27 years ago. I thought it might be nearing the end of it's life due to old age problems. It was surging and hiccupping. The idle was getting pretty rough and the hole shot was getting pretty weak. The top end was okay at 38 mph but I could only now turn up 5100 rpms at WOT. Also the low speed performance was not all that good either with vibration and out of tune and song sound. I thought we were near the end and a very expensive 4 stroke upgrade was going to be in my future. I could make that happen from a financial perspective, but it would be a stretch and with college for my kids in the next 5 years I would really have to think long and hard about this...
I was talking to a mobile marine mechanic that works out of the marina I keep my boat at about these problems. He gave me a few suggestions to look into but he didn't want to work on such an old motor due to the time involved to trouble shoot everything and he was very busy. I was pretty discouraged. One point he made clear was to run a compression check on all 6 cylinders BEFORE I did anything or spent any money on parts. That made a lot of sense to me. So armed with my friends compression gauge I went to the marina to run a compression test on all 6 cylinder to see what I had. Honestly, I wasn't sure what I would find and had serious doubts. I warmed the motor up with a little ride on the lake. Motor was not running too good as mentioned above. I pulled into a covered wet slip and commenced to do the compression check. The first cylinder was 125 psi. I thought that was excellent and my attitude went from near death motor thoughts to some optimism. The # 2 cylinder was 126 psi, #3 was 125 psi, # 4 was 122 psi. I was pleased but guarded thinking the next cylinder would be 50 psi or something like that. BUT, #5 was 120 psi and the last cylinder....drum roll please....was....120 psi!! I was very happy with these readings needless to say! Well buoyed by this good news I walked over to the marine mechanic to share my great news. He said that was surprising and actually pretty impressive for the age of the motor. BUT---He still declined to work on the motor. I left to go back to the boat with a deflated attitude. I tinkered around on the motor but nothing really helped. New spark plugs etc... When leaving the marina the mechanic whistled and called me over to the boat he was working on. I thought he might have changed his mind and wanted to earn his $95/hour and take a shot at my motor. NOPE! still not interested, BUT he knew a retired Yamaha certified mech that was good with older carbed engines and gave me his phone number. I called the retired mech (Travis) and told him my sorrows. He said he would try to help. He loves old Yamahas and bought into my troubles. We agreed on a time to meet and he would bring his tools, meters and years of Yamaha experience. More below. |
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So Travis picks and prods at the engine. Starts then cuts off, revs, etc while I assist as his helper and boat driver.
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So we did the following repairs:
1) Replaced 3 ignition coil assemblies 2) Replaced all 6 spark plugs 3) Rebuilt/Cleaned one of the 3ea 2-bbl carbs (One bbl was completely clogged) 4) Adjusted and synchronized all the carbs (3) 5) Adjusted the TPS (Throttle Positioning Sensor) - It was way off Total parts bill = $293 Total Labor = $220 Total Bill = $513 |
You can't beat that!!
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The results were OUTSTANDING!!
The chart below summarizes the New performance: RPM SPEED (MPH) GPH MPG 800 4 1.0 idle 3900 28.5 4000 29.1 4100 30.5 10.5 2.90 4300 32.3 11.5 2.81 (Optimal Cruise) 4600 35.2 13.3 2.65 5000 37.3 15.0 2.48 5400 40.8 18.4 2.22 5700 42.8 20.3 2.11 5800 43.3 21.2 2.04 (WOT) The "Hole shot" was VERY strong with this 17" pitch prop. I was totally impressed by this tuned up 27 year old 2 stroke Yamaha motor and had to share this. Test conditions: 30 gallons of Fuel Light load One driver only Aluminum prop in good condition ( 3 blade x 17" pitch) Head Temp 140* Engine water temp 130* |
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Retired !!! :eek::eek::eek: at what 45 ?? I need to find a new profession...:rolleyes: |
Jim that's BS!!! You are just pulling our leg!! There is no way you pulled that off for a smooth $513, most boat repair shops don't get a "woodie" until the cash register hits at least $1,500!!! When it gets to $2,000 and up they are in full happy mode!!
Seriously, you know you do have to maintain these more than once every 25 years??? :) |
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Roll eyes. |
Add in a new set of fuel pumps and you'll have refreshed the entire fuel system :) on that motor. The ethanol fuel ruins my Merc Fuel Pump Diaphrams. After about 2 - 3 seasons they get hard stiff like potato chips. Just something to consider if your fuel pumps are 27 :)
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OK...I'll give you some credit, it hurts to do that!! But I just thought "maintenance" in your book was putting gas in the tank and two stroke oil in the gas :)
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Nice. Congrats. I would bet a new modern SS prop would give you 2-3mph and better fuel economy as well.
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Salt Water Merc Ran 28 Years
I replaced the original '76 Merc 150 straight six on my '76 Seafari in 1985 with a Merc 150 V6. This second engine ran for 28 years until the summer of 2013 with the first 15 years in salt water in south Florida. The remaining usage was on SC fresh water lakes for watersports. It received relatively routine maintenance, but the carbs were never rebuilt (thanks to annual replacement of the water separating fuel filter) until 3 years before she died. The mechanic who gave me the low-compression death warrant told me I got twice as much out of it as I should have considering salt water usage!
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Jim,
Sounds like that was money well spent! I guess a motor as new as an '88 (my old carb'd motor was a '75 vintage) probably has an oil injection system. However if it just mixes oil with the gas upstream of the carbs instead of injecting oil directly into the bearings and cylinders, it's still basically the same as running premix. If that's the case, running the motor with a plugged carb jet starves that cylinder for OIL as well as fuel, and that can quickly kill a motor! I had a plugged jet on my old motor one time, but since I was definitely NOT overpowered (~100-105 prop hp on a 20), it was pretty obvious I had a problem, so I discovered it right away. However, one potential issue with a bigger motor that will push a boat over 40 mph is you can have a potentially fatal problem like fuel starvation, but with lots of power available, it's easy to just bump the throttle up a bit and never notice it until it's too late! If you consider that modern motors are calibrated to run leaner mixtures for better fuel economy, and add e-10 (10% ethanol) gas that contains extra oxygen and burns even hotter if the mixture gets lean, there is not a lot of margin between normal operation and a slight amount of fuel starvation that can lean out a cylinder enough to overheat a piston/score a cylinder, etc.! The older carb'd motors like yours were jetted on the rich side of optimum for maximum power, so it was hard to plug 'em up enough to hurt 'em, but that's no longer true for the modern "clean technology" motors, either 2 or 4 stroke! I'd advise anyone running a modern engine to be very cautious about just bumping the throttle up a little more if it doesn't seem to be running right! While some of the bigger motors have knock sensors or O2 sensors that may detect lean operation, I believe a little extra caution is warranted if a modern motor seems to be down on power! Although I've never had that sort of problem on my E-TEC, my dealer has measured the restriction in the boat's fuel system, I run a vacuum gauge downstream of the fuel filter to check for plugging, and I watch the Throttle Position Sensor reading vs. rpm relationship for anything unusual. One time that alerted me that I had forgotten to pull up the swim ladder, so it seems pretty sensitive! If I was running a 4-stroke and didn't have a TPS readout, I think I'd monitor intake manifold vacuum, as it's also a very good indicator of engine load. |
Thanks Denny. My engine is oil injected and the oil is injected AFTER the carb. Thank God or I would have blown motor 2 years ago. I'm ashamed to say that I have been running on five cylinders for over two years!! 97 hours at around 188 hp. My motor was strong with the compression and I just bumped up the throttle as you mentioned. I got real lucky on this one and learned a lesson. Now with all 6 cylinders and tuned up it runs like a raped ape!!
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Jimbo, you may have earned "Slacker" status on this one...:eek:
GFS, you are off the hook...;) Humm, I will have to think of a new sub title for 77SceptreOB.. :D Suggestions are welcomed ! |
I'm thinking Ken, maybe I'll order up some "pink panty drop" moonshine, which Jim seems to prefer, take a few sips and give it some deep thought.
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Hey, that motor ran pretty darn good with only 5 cylinders! It was only when some of the old coils and the TPS got out of adjustment that it started running crappy. Yamaha builds one heck of a motor for psuedo slackers like me...LOL!! The Motor runs unbelievable good now. But this motor HAS had a lot of work done and upgrades over the years. Some include:
Rebuilt power head in 1998 Completely new lower unit in 2009, rebuilt in 2011. (Do to bad shaft seals) New fuel pumps (2) and 3 rebuilt carbs in 2009 New thermostats (2) in 2011. New empeller in 2011, 2013, and 2015. lower unit gear lube changed every year since 2010. 3 new coils in 2010 and the other 3 replaced in 2015 Only non-ethanol fuel used since I took over the boat in 2009. |
Some videos of the motor running after the tune up. Quality boat porn!
At Idle https://youtu.be/BRiv0JbMtTI Hole shot! up to 5800 rpms https://youtu.be/rjAOIU9ueBk Hole shot # 2 https://youtu.be/PALpYABFKRk On a SLOW plane https://youtu.be/3i5pgwqj0Ek |
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