Outboard motor w/ HIGH hours??

77SceptreOB · #1 08-23-2010, 08:53 PM

I've heard many guys say that their Powerhead blew but "It had a bunch of hours on it" Other experienced capts have said that a recreational boater (approx 75hrs/yr) will rarely wear out a motor, and it's all the little things that ultimately dooms the motor. Looking for some opinions on what constitutes a High Hour motor. Are we talking 500 hours? 1000 hours, 2000+ hours? I know this is VERY subjective question! okay, Fire away.

Bigshrimpin · #2 08-23-2010, 11:54 PM

Don't get hung up on hours . . . unless it's a 4 stroke or a lower unit. A leak down test, 1/2 hour ride, and a general inspection will reveal nearly everything. Most low use saltwater motors will die a early death (run lean, overheat, or corrode)

pelican · #3 08-24-2010, 08:34 AM

Quote:

Don't get hung up on hours . . . unless it's a 4 stroke or a lower unit. A leak down test, 1/2 hour ride, and a general inspection will reveal nearly everything. Most low use saltwater motors will die a early death (run lean, overheat, or corrode)

how true is this !! very well said...average use of a boat is 40hrs per year-hard to believe huh ? i have customers with 2 stroke carb'd yamaha engines with well in excess of 4000 hrs-nothing but routine maintance-water pumps,thermostats and head gaskets...i have customers with big hour hpdi and ox66 injected engines too...it's all about how the engine's taken care of,an engine sitting around,just like "big shrimpin" said,it's gonna corrode and die young...

77SceptreOB · #4 08-24-2010, 08:53 PM

Quote:

A leak down test....

Is that the same as a compression test?

Old'sCool · #5 08-25-2010, 11:28 AM

Quote:

A leak down test....

Is that the same as a compression test?

No. It measures leak down after being pressurized. The ability to hold/maintain pressure.

77SceptreOB · #6 08-25-2010, 09:25 PM

Aren't pressure and compression the same? A compression test measures how much psi (pressure) the piston / cylinder can achieve,right?

Fr. Frank · #7 08-25-2010, 11:09 PM

Quote:

Aren't pressure and compression the same? A compression test measures how much psi (pressure) the piston / cylinder can achieve,right?

Not exactly. and Yes.

A leak-down test measures how long it takes pressure to leak out past the rings (& valves for a 4 stroke). So if you get 130 lbs of compression in a cylinder, that may be good. But if you pump in 100 lbs of air pressure, how much pressure do you still have after 5 minutes of the piston sitting at TDC.

So instead of measuring pressure, a leak-down test measures pressure loss. Another name for this test is a cylinder leakage test.

Old'sCool · #8 08-26-2010, 10:03 AM

All the compression testers I've used have a check valve that prevents leak back. The needle stops and stays at the uppermost reading and you manually release the pressure. A leakdown tester's indicator is free to show a lower reading as pressure drops.

JohnB · #9 08-26-2010, 10:19 AM

With average maitenance, ob motors last a long time. The only new thing is alcohol, and it is killing a lot of older 2 stroke carb and tbi efi motors. Crud in the fuel system will lean out a cylinder and than you got problems. I had a merc efi with over 2500 hours on it that ran like a top until the crank broke. I think most 2 strokes will get to 2000 hours with maint. I am not sure on the 4 strokes, more moving parts. The SeaTow guys around us are running Suzuki 4 strokes and replace them every 2000 hours and don't seem to be having any problems with them. Time will tell. Suzuki warranteed mine for 6 years, and I average 350 hours a year.

Fr. Frank · #10 08-26-2010, 12:12 PM

Maintenance is the key. When I sold my first SeaCraft, a '73 Seafari, it had 1700 hours on a '73 inline 6 cylinder 150 hp Mercury, and had 125-135 lbs of compression across the board still. I changed spark plugs, gear oil, and impeller every year or 100 hours. I checked ignition timing every year. (Never had to adjust it). I always ran the oil at 40:1, not 50:1, on the advice of Frank Brown. The boat had been in my family since new, and always got excellent mechanical maintenance.

My cousin ran the boat hard for two more years before re-powering with a Black Max 175. The inline 150 "Tower of Power" was still running great when he sold it with over 2000 hours on it. He just wanted more power. He didn't get it. Turned out the boat was faster and used less fuel with the inline 150.

Man, I LOVE those inline 6 Mercury motors.