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Dive Boats 4-Sale Have a dive boat you want to sell? Post photos and a good description, and you may just have some success.

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Old 09-14-2008, 02:48 PM   #16
Bulit7
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Re: How many hours does an outboard last?

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What a coinsedence! I am selling a boat with twin 115 suzuki 4 strokes. I am going to tell you this: any internet mechanic who tells you that these motors are no good after 1500 hours has no clue what they are talking about. I have friends with the same motors one has 7000 hours on them and is still running. The other has 3000 and no problems. To say you will need a new lower unit around 1500 hours is ridiculous! Obviously routine maintenance is necessary and as long as the motors are well kept they will run for a long time.

My motors have 1200hrs on them and I maintenance them myself. Have never had a problem. Just pulled compression for a potential buyer when the motors are warm They averaged 235psi +/-2-5psi per cylinder (which is typical). Cold the motor compression was 180psi +/- 2-5 PSI. Both motors. I would suggest speaking with people who have owned these motors or an outboard marine mechanic to get more information.
What you are doing when buying an outboard engine is making an educated guess as to haow that engine was cared for and used. Lower hours equals less problems. I would avoid high engine hours unless the price wwas very right. 235 psi... not sure you would see that on a new engine.
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Old 09-14-2008, 05:44 PM   #17
Tyler Durden
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Re: How many hours does an outboard last?

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Originally Posted by Bulit7 View Post
What you are doing when buying an outboard engine is making an educated guess as to haow that engine was cared for and used. Lower hours equals less problems. I would avoid high engine hours unless the price wwas very right. 235 psi... not sure you would see that on a new engine.
Also, with the newer motors, you can get a readout at the mechanic of all the hours running binned by RPM range. That way, you can find out if a motor spent 95% of its life in the >3500 rpm range, or 95% of its life in the <1500 rpm range (trolling). I would have no issues buying a 4 stroke that had 1000 trolling hours on it.
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Old 09-14-2008, 07:01 PM   #18
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Re: How many hours does an outboard last?

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Also, with the newer motors, you can get a readout at the mechanic of all the hours running binned by RPM range. That way, you can find out if a motor spent 95% of its life in the >3500 rpm range, or 95% of its life in the <1500 rpm range (trolling). I would have no issues buying a 4 stroke that had 1000 trolling hours on it.

Just for you to have an idea of how different types of use and abuse affect a motor:

I have a customer that has a lot of money and does not care about wear and tear. He has a pretty badass 2004 36 foot CC with triple Yammies 4-strokes on it. He goes to the Bahamas exclusively and wants to get there and back in record time. Engines have about 700 hours on them and last service we had slightly milky lower unit oil so I replaced the prop shaft seals on all three. They sealed and passed the pressure test. A month later I pulled the drain plugs to check and we had water in there again. Rebuilt all three drives. New prop shaft and drive shaft. The old ones had groves in them from the seal. I assume that it was from all that jumping over waves with the boat. The times I went out with him, we would run to the fishing grounds at full bore(5200rpm). A good percentage of the time we were airborne.

Best bet is to buy a boat that was slightly used by someone that had little time for it. There are a lot of them out there.

It is good that these newer engines can be tracked for abuse, but you still need to hire a mechanic to get you a printout.
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Old 09-14-2008, 08:16 PM   #19
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Re: How many hours does an outboard last?

Compression numbers are correct cold 180, warm and wide open 235. The reason I run it both ways is because some mechanics tell you to pull proper compression the motor needs to be warm and throttle wide open, others say it doesn't matter.

I agree that if someone abuses a motor it will have issues. Although most people are not made of money and do understand how to operate a boat. My average cruising speed is 3800-4100. Very seldom do I pin it (occasionally in the river to clean out the carbs). It's all about preventative maintenence. I have no problems buying used motors because I know tell tale signs of issues that cannot be dressed up.

Anyone interested in buying a boat with used motors and does not have a clue should pay a certified mechanic to complete a survey. Most will do this for around $200.
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Old 09-17-2008, 04:33 PM   #20
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Re: How many hours does an outboard last?

Unless I am missing something, 235 psi cylinder pressure equates to about 16:1 compression ratio. 235/14.7

I don't know about Suzuki but a Yamaha 4S 115 or 150 is gonna be under 10:1.

Me thinks you may need a new compression gage. Your compression should be around 135-145 psi.
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Old 09-17-2008, 04:53 PM   #21
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Re: How many hours does an outboard last?

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Unless I am missing something, 235 psi cylinder pressure equates to about 16:1 compression ratio. 235/14.7

I don't know about Suzuki but a Yamaha 4S 115 or 150 is gonna be under 10:1.

Me thinks you may need a new compression gage. Your compression should be around 135-145 psi.
I was not going to say shit, but since you brought it up, Highest comp I have seen is 180-200 on a brand new 350ci engine, 125-140 on a two stroke outboard and 160-175 on a 4 stroke outboard. Who knows, maybe the dude gots himself a one off badass outboard!
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Old 09-18-2008, 05:08 PM   #22
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Re: How many hours does an outboard last?

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I was not going to say shit, but since you brought it up, Highest comp I have seen is 180-200 on a brand new 350ci engine, 125-140 on a two stroke outboard and 160-175 on a 4 stroke outboard. Who knows, maybe the dude gots himself a one off badass outboard!
It's a brand new gage, not sure how it would be reading incorrect already, Ill pull again this weekend.
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Old 09-18-2008, 05:57 PM   #23
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Re: How many hours does an outboard last?

Cold compression spec on my Honda 130s is 200psi, 9.5:1 compression. They test with my gauge @ 190-195.

Properly cared for 4-strokes can run for 1000s of hours.
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Old 09-19-2008, 12:20 AM   #24
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Re: How many hours does an outboard last?

You are checking cylinder pressure, not compression ratio. Cylinder pressure can be changed on a 4 stroke with cam timing, and a different cam. Radical cammed (4 stroke obviously)engines that make power at high RPM usually have retarded cam timing and low cylinder pressure-at cranking, and high compression ratios like 12 to 1 and higher. Simply advancing the cam timing will bring up the cylinder pressure. Changing the cam to less overlap, less duration and advancing the cam timing will really bring up the cylinder pressure-usually too much, if 12 to 1 comp ratio is kept. 2 strokes really cant change cylinder pressure as they dont have cams, so the CP is the same unless the engine has new pistons with bigger domes, or smaller combustion chambers or worn out or carboned rings. My zillion hour Evinrude loopers both have 130 lbs on the gauge. Supposedly they were rebuilt, but they still work good. Back on topic, a cylinder is supposed to be oilled also for best results. What you are looking for is as close to factory specs, and less than 5-10% variance between them. Each engine will be different specs.
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