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Merc 300 xs optimax 3.2 racing

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Old 04-11-2010, 08:01 AM
  #11
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Strange

I have 296hrs and 298hrs and love my motors. The air compressors (both) blew at 2350 and change.

I believe the cowling has a design flaw as it sucks in salt water like no tomorow on our cat boats that generate speeds over 100.

Lowers have been great but you need to buy the seal/spacer kit from Mad EFI to keep the water pump seal from pushing out and pushing your oil out. I would avoid welded in hub props, Merc hubs are easier on the gearcases for load and unloading.

My motors are late 06 models.
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Old 04-11-2010, 11:58 PM
  #12
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Originally Posted by AppSysCons View Post
My 2007 30/308 Skater came from the factory with T/300XS. After 3 weeks (30 hours), one motor melted piston 5, and ventilated the block with the connecting rod. The power head was on national backorder so I was down from May 27 to Sep 28.

Since then the only other engine failure was a burned up coil and ignition harness at 97 hours. Presently, I have 120 hours on one and 90 hours on the other, but for some reason the computer shows 120 & 118 hours?

The real problem has been the lower units. I am on replacements 5 and 6. I was cracking them like clockwork, and other owners have reported the same thing.
Appsyscon,

I've heard of issues with lowers with the 300 XS. You mentioned cracking them. Do you attribute that to water getting into them or that they are taking a beating from being on a cat?
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Old 04-12-2010, 12:08 AM
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Well I have 3 hanging off the back of the Concept and love the engines. We have close to 80 hours on them and running great.
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Old 04-12-2010, 08:30 AM
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Quote:
Originally Posted by AppSysCons View Post
My 2007 30/308 Skater came from the factory with T/300XS. After 3 weeks (30 hours), one motor melted piston 5, and ventilated the block with the connecting rod. The power head was on national backorder so I was down from May 27 to Sep 28.

Since then the only other engine failure was a burned up coil and ignition harness at 97 hours. Presently, I have 120 hours on one and 90 hours on the other, but for some reason the computer shows 120 & 118 hours?

The real problem has been the lower units. I am on replacements 5 and 6. I was cracking them like clockwork, and other owners have reported the same thing.

Did they do anything different to the sportmaster lower units with the 300XS? Reason I ask is I just ordered two for my Spectre. I have been running 300 Promax's for the last five years and have had zero problems with my sportmaster lowers. I change the lower unit lube in the fall (October) and then once again mid summer (July). No problems. Usually boat from May thru September.

Thanks.

Mike

Mike
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Old 04-12-2010, 09:27 AM
  #15
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Originally Posted by mikesufka View Post
Did they do anything different to the sportmaster lower units with the 300XS? Reason I ask is I just ordered two for my Spectre. I have been running 300 Promax's for the last five years and have had zero problems with my sportmaster lowers. I change the lower unit lube in the fall (October) and then once again mid summer (July). No problems. Usually boat from May thru September.

Thanks.

Mike

Mike
Mike,

I change my gear lube every 20 hours, and have not had any water intrusion or internal part failures.

I have been cracking the housing, in the exact spots as others have.

I suspect the older castings were stronger, and probably from a different supplier.
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Old 04-12-2010, 09:31 AM
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Quote:
Originally Posted by Powerplay25 View Post
Appsyscon,

I've heard of issues with lowers with the 300 XS. You mentioned cracking them. Do you attribute that to water getting into them or that they are taking a beating from being on a cat?
No water getting in to mine. The cracks are not in the area that contains the gears or gear lube.

They are mounted high, it is a fast cat, but that is what the lower unit was designed for.
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Old 04-12-2010, 12:04 PM
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Quote:
Originally Posted by AppSysCons View Post
Mike,

I change my gear lube every 20 hours, and have not had any water intrusion or internal part failures.

I have been cracking the housing, in the exact spots as others have.

I suspect the older castings were stronger, and probably from a different supplier.
Gotcha. Thanks for the info.

Mike
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Old 04-12-2010, 01:27 PM
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So what you guys are saying is once I get my engine problems worked out I'm going to have drive failure??
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Old 04-12-2010, 01:31 PM
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So what you guys are saying is once I get my engine problems worked out I'm going to have drive failure??
All I can do I is share my experiences, and let you draw your own conclusions.
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Old 04-12-2010, 09:06 PM
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40 hours port lower blew. May or may not have to do with testing props and motor heights. Clutch dog shattered

100 hours starboard power head gone- shot some thing through the side of the block into the side of the computer- think it was #2 but I know very little about motors

117 hours starboard lower blew after about 5 hours on lube, checked port gear lube and looks pretty bad- mechanic says he thinks some thing is going to let loose sooner than later. Snapped the prop shaft- like 1"+ solid metal!
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