MERC. 450hp missing when HOT

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TATER8

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Jul 4, 2002
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I have an 1988 BAJA sport 240 with an 400 small block(77) put in 4 years ago done up to marine specs. I took the boat out 5 times with out a problem and it started missing at top speed and now when it gets hot it will miss all the time.<br />When you start it up it doesn't miss a beat until about 15 min of driving. We changed coil, plugs and wires, distributor and cap, rotor, fuel sep.,etc.. we also checked fuel pump and filters.<br />I would appreciate any suggestions! thankyou
 
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ODDD1

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Re: MERC. 450hp missing when HOT

tater, you say it runs ok cold, misses wot hot....you are headin in the same direction I would, weak ignition or a fuel supply prob...whose ignition and how fast you spinnin this motor? If you are pushin the rpm up there, and got ALOT of cam, have you thought about hammered out valve springs? this is where they show up first...
 
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TATER8

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Re: MERC. 450hp missing when HOT

I have a thunderbolt ignition which I tried a new one that didn't help. We had a mac. go for a ride and we moved wires around and it made it work a little better so I started redoing all the grounds which helped. The boat will go up to 65mph<br />@ 5100rpms and will go up to 5300rpms. The next step is the valves are getting setup and we are putting bigger jets in the holly 750 car.<br />thankyou for the info tater
 
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