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| Low rpm under load https://www.smwebhead.com/phpBB3/viewtopic.php?f=6&t=8390 |
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| Author: | Second Winns [ Mon Sep 12, 2011 4:42 pm ] |
| Post subject: | Low rpm under load |
My 2002 268 Vista (5.7 Gxi Volvo Penta) will not go over 2800 rpm under power (goes to 4-5,000 rpm in the slip with no load) and misses out at idle. Have replaced all plugs, cap, rotor, distributor module and pick up as well as fuel filter. Looked at 4 of the plugs after test run and all 4 were evenly carboned up. Anyone had similar problem and if so what is the cure? Marina mechanics have not been able to help. Ken |
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| Author: | aguyindallas [ Mon Sep 12, 2011 6:35 pm ] |
| Post subject: | Re: Low rpm under load |
I would empty the fuel filter into a jar and see if you have any water separation. |
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| Author: | Cap'n Morgan [ Mon Sep 12, 2011 6:59 pm ] |
| Post subject: | Re: Low rpm under load |
I had the exact same symptoms with our 268 Vista. Before you go any further, check the compression on all 8 cylinders and report back what the readings are. |
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| Author: | wkearney99 [ Tue Sep 13, 2011 6:43 pm ] |
| Post subject: | Re: Low rpm under load |
Loads require fuel. RPMs with no load don't require much gas. But a load will require a lot more. I'd wonder about your fuel pump being able to deliver enough volume at the pressure needed under load. It's typical to test this by putting a fitting in-line on the fuel hose to measure the pressure. But checking cylinder compression is also a good idea. |
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| Author: | jsimon [ Tue Sep 13, 2011 7:36 pm ] |
| Post subject: | Re: Low rpm under load |
Is the hull bottom painted? Our last boat a 268 with a 5.7 volvo wasn't bottom painted, we left it in for 6 weeks, it wouldn't even get out its own way!! Not sure what the rpms in but it would even get up on plane it had so much s**t on it. just a thought |
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| Author: | Second Winns [ Tue Sep 13, 2011 9:04 pm ] |
| Post subject: | Re: Low rpm under load |
Was able to borrow a friends compression tester today and found that two cylinders have almost no compression. Have a boat mechanic working on boat tomorrow to replace head gasket and anything else that is wrong. Tried to get marina to check compression two weks ago when problem started. Compression test 1= 123 2= 117 3= 005 4= 110 5= 015 6= 108 7= 116 8= 108 Gee I wonder why it didn't run correctly. |
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| Author: | Lakebum [ Tue Sep 13, 2011 10:01 pm ] |
| Post subject: | Re: Low rpm under load |
That sucks, I've had head gasket and valve problems with both of my engines (5.7gsi). I ended up having the heads reworked, new valves, and gaskets on both engines. Port side 492 hours, starboard 517 hours. Neither engine has ever been very hot (over 200) and mostly real gas. I had 2 mushroomed valves and even though these are vortec heads, the machine shop guy said he's seeing more and more of this because of sh#tty gas. Not sure what really caused it but hope yours turns out alright. Good luck. |
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| Author: | Cap'n Morgan [ Wed Sep 14, 2011 6:40 am ] |
| Post subject: | Re: Low rpm under load |
Thanks for the reply. Two adjoining cylinders were low on our 268, but the result once the head was disassembled, was the worse case scenario. Hope yours is just the gasket. |
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