lost power on Ford 460

R

R Kraft

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I was running at 35 mph, now when I accelerate it backfires, and tops out at 18 miles an hour at 4200 RPM. You can feel the weakness. The local mechanic replaced the electrical coil, points, <br />plug wires, distributor cap, and overhauled the carburator.<br /><br />He is running out of ideas. :eek:
 
A

Alrobot

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Re: lost power on Ford 460

Wow, that sounds serious. Have you done a compression test yet. Points???, hasn't everyone switched over to a Pertronix yet. Does it rev okay in nuetral, jet or prop?<br /><br />Al...
 
R

R Kraft

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Re: lost power on Ford 460

We havn't done a compression check yet. We are still hoping for a simple solution. We did change the points. What is Pertronics? It does rev ok when in neutral.<br /><br />Randy
 
R

R Kraft

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Re: lost power on Ford 460

One last answer. It is a prop drive, and we put a new prop on it.
 
Boatin Bob

Boatin Bob

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Re: lost power on Ford 460

I would assume that the timing was checked/set with the ignition work but did your mechanic or you check the timing advance in the distributor? I've heard of the weights getting rusty or the springs breaking and not working so the timing doesn't advance with the rpm's, or what about the ESA module, on the original ones it can be activated forever even though the over stroke switch is supposed to prevent that, I think the newer ones have a built in timer. Did this just happen all of a sudden or did it get progressively worse?
 
R

R Kraft

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Re: lost power on Ford 460

I think it happened over time. I do not think it worked great one day and then bad the next. It is hard to tell, because I go through props and run it on a river, where it is hard to tell how fast I am going. <br /><br />I now take the speed off a GPS<br /><br />Thanks again for your help.
 
A

Alrobot

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Re: lost power on Ford 460

Pertronix is the best thing since sliced bread. www.pertronix.com Check it out, you will never have to change points again. I would also have to agree with the timing issue...
 
D

DJ

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Re: lost power on Ford 460

Check timing! Did it jump a tooth on the chain(timing)?
 
Bob_VT

Bob_VT

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Re: lost power on Ford 460

If you have the right parts in an engine then the two pieces of the puzzle to make it run right are ignition and fuel.<br /><br />I agree with djohns and I would check the timing and start from a static time position. Check your TDC and distributor. Check for an adaquate spark (coil gone bad????).<br /><br />Now check for fuel and quality and quanity of fuel. Did you get a bad tank of fuel?????Bad fuel will raise cain with even the best running motor. Check the filters and check the fuel pump output. I just installed a new pump in my I/O last week. <br /><br />Bob
 
A

Alrobot

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Re: lost power on Ford 460

We are dying to know what happened.
 
R

R Kraft

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Re: lost power on Ford 460

Update!<br /><br />I found a new marine mechanic and he found a bad spark plug. This makes all 8 cylinders run and the RPM's are up where they belong. Instead of 18 miles and hour I now get 23 miles an hour (it was going 35) and now no backfire. <br /><br />We still don't know why it is so slow. It feels like we are dragging an anchor. I have tried a couple of different props and it doesn't make any differrence. I don't see any binding on the prop shaft (like a tangled rope).<br /><br />It feels smoth when we run it. Is it possible for something could be binding in the lower unit? The boat has set in the water all summer, the mechanic thought maybe the growth under the boat was slowing it down, but it doesn't look excessively bad and that is a drastic speed drop. <br /><br />Any ideas would help.<br /><br />Randy
 
R

R Kraft

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Re: lost power on Ford 460

If I had a smaller engine the local mechanics could hook up a "dyno" to the engine to see if the proper horsepower is coming out the engine. Is there any way I can check to see if the proper horsepower is coming out of a 340 hp engine. The local mechanics say there dyno's only go to 200 horse power.<br /><br />Hower do I check to see that the proper power is coming out of the outdrive?<br /><br />Thanks again.<br /><br />Randy
 
Boatin Bob

Boatin Bob

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Re: lost power on Ford 460

I know you said you tried a couple of props with no difference but if the pitch is different you should see a difference in both MPH and RPM's, smaller pitch should give higher RPM's and better hole shot, but lose a bit of top end, larger pitch will be more sluggish out of the hole, reduce RPM's but give a better top end speed. General rule of thumb is 200 RPM's for every inch of pitch change. I have a pair of 460's (OMC King Cobra's) in my 35 ft cruiser. They have 15 x 17 SS props and WOT is about 44 MPH at 4500 RPM.
 
R

R Kraft

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Re: lost power on Ford 460

Update!<br /><br />AS I noted earlier, when the mechainc put in a new spark plug I went from 18 mph. to 23.5 mph After I cleaned the boat bottom my MPH went up to 30. If I clean the bottom better, I can probably get a couple more MPH. This still seems slow. 30 mph on a 26 foot cruise with a ford 460, but I can live with it.<br /><br />New problem. Actually it is an old problem, but I have been looking for someone with Ford 460 experience to help me.<br /><br />The exhaust boot on one side overheats and splits if I idle more than a few minutes. At idle, the temperature will reach well over 200 degrees, when I speed up the boot cools down. I have tried lots of things. The OMC King Cobra out drive has been apart several times.<br /><br />In talking to Ford, they said one side of that engine justs runs hotter. At this point I think the manifold is partially blocked and the engine runs hotter on that side by nature. I am not ready to spend hundreds more on a new exhaust manifold, just to find out once again, that this was not the problem. The spot on the boot that gets hot is relatively small, I am thinking of cutting an aluminum beer can and lining that part of the boot.<br /><br />Any suggestions would be helpful.<br /><br />Randy<br />Any suggestions, would help.
 
R

R Kraft

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Messages
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Re: lost power on Ford 460

update!<br /><br />After putting in the new spark plug I went from 18 mph to 23.5 mph. I then cleaned the boat bottom and went from 23.5 mph to 30 mph. I can live with this, even though it would seem that a ford 460 with an OMC king cobra should go faster than this on a 26 foot cruiser.<br /><br />New problem, or should I say old problem that I never fixed. When I idle the rubber exhaust boot one one side over heats and splits. After trying many things, I think that the engine simply runs hotter on one side (this comes from Ford) and that the exhaust manifold is partially blocked. I am not ready to purchase a new manifold to test another theory. I have learned to raise my rpm's if I am just sitting at idle. The spot that overheats is very small, maybe 2 square inches, I am thinking of cutting open an aluminum beer can and lining that part of the boot.<br /><br />I am looking for someone that has experience with the Ford 460 and OMC King Cobra, that might have had this problem. If I could find an exhaust manifold for this engine at a good price, I would purchase it.<br /><br />Thanks<br /><br />Randy<br />1-800-454-3483
 
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