454 Loss of Power

kwinters · Post by **kwinters** » Thu Sep 03, 2009 2:30 pm

Anyone shed some light on Marine Power 454's, loose power then regain, rough idle, timing does not advance. New cap, rotor, wires, plugs, distributor, coil and fresh rebuilt carb. There is a small modual, not a ECM, that also is tied in next to the coil, not new. There is a lot of noise from what seems like the front end of the engine. Have run without belts to eliminate fresh water pump and alternator. Down to raw pump which is 3 months old, timing chain and sticking valves. Another member talked about the timing chain on 454's. The are 98's and wonder of the sprockets are nylon. Any ideas would be helpful.

franklyprice · Post by **franklyprice** » Thu Sep 03, 2009 3:25 pm

How many hours on the engines? If less than 1500 I would not be too worried about the timing chain. I would do a compression check just to rule out internal things , then look at ignition, specifically the distributor, cap and rotor. Did you change the parts trying to fix the problem or did it start acting up after some work was done? If you had a point distributor I would say it might be a condenser but it must be an electronic ignition. Also find out why the timing won't advance, take the cap off and try to turn the rotor or at least see if there is an internal advance mechanism. If not it should electronically advance , controlled by some sort of module.I would put my money on some sort of spark issue but you should rule out the easy stuff. Check the initial timing (10 degrees or so) and make sure you don't have a vacuum leak.

kwinters · Post by **kwinters** » Thu Sep 03, 2009 3:36 pm

950 hours on the engine. Yes, had issues before we started. Extream corrosion inside the distributors (electronic) but the engine ran well. This just started again after about 100 hours. The engine runs very richand you can not adjust it out with the carb air mixture screws. You can sit on bridge and see the black smoke come and go with the rpm dropping and comming back up. I have a vacumn gauge on that engine and it moves slightly as the rpm varies by 50 to 150. It appears that the burning of the fuel is comming and going. At RPM"s over 2600 the Quads are screaming, no power and the vacumn drops to 5 or less. Thanks for your input.

otf · Post by **otf** » Fri Sep 04, 2009 3:22 am

Is it a 33 and what year/tank. I would say the timing advance is the place to start, short of the "lot of noise from the front of the engine". That makes me wonder about compression first. Simple enough to check. If that's ok, the inside is probably working, chain is ok - valves working. Also what was wrong with the carb, and buildup on it before rebuilding it? If that's ok, back to the timing advance which was originally a problem with the distributor, and still doesn't seem fixed. Just an idea, let us know how it turns out.

Rick · Post by **Rick** » Fri Sep 04, 2009 3:29 am

I agree, compression check. When I had a hung valve, black smoke lead me to it. Rick Ticket 85 SF Merc 454 MPI's Falmouth, MA

CB35 · Post by **CB35** » Sat Sep 05, 2009 6:41 am

Bad fuel? Was there any black goo on the carb? Fiberglass tank? Sounds to me like bad fuel or the dreaded black goo.

captgene · Post by **captgene** » Sat Sep 05, 2009 9:03 am

Could be goo, but recheck the wires just for fun. I messed up something silly like that on the old 7.4s. I think I transposed #1 & #8 and it caused similiar effects. Gene Dugan Boca Raton, Fl. "Nauti Marie" 1989 33 FBC 2007 8.1 Crusaders

franklyprice · Post by **franklyprice** » Mon Sep 07, 2009 4:22 pm

The mixture screws on a carb are for idle only, so wouldn't expect any change. I would try changing carbs with the other engine to rule that out. If that doesn't do anything you can swap distributors also . Don't rule out the posibility of faulty replacement parts. New rotors , caps or wires can be defective, especially if you're not buying OEM. What do you mean when you say it started again after 100 hours? Is this a problem that comes and goes? Could you be more specific about when it started having problems and what you did when it ran well? Do that compression test, Rick has a good point about stuck valves.

Miss B · Post by **Miss B** » Mon Sep 07, 2009 7:47 pm

Get you a vacuum gauge and hook it up to raw vacuum from the manifold. Read the inches of vacuum and whether the gauge is steady, or pulsating at idle, then at incrased RPM's. Crack your throttle open to about 3000 RPM, hold it steady, and read the gauge. Then, let the RPM's drop back and see what the gauge does, is it steady, fluttering, or goes up to high reading, say 23 - 26 inches. Compare the readings with the chart on that came with the gauge. You can get a good vacuum gauge for about $20 and it should be part of every tool box if you have a gas engine. Vacuum gauges are great cheap ways to check the internal conditions of your engine. Don't go screwing the carb screws or timing until you get your vacuum readings first. Next, put a timing light on the # 1 plug, its location will be shown on the intake manifold. Watch what the timing light does when the engine is running at idle. The mark should be steady and not jumping around. Then, take the RPM's up to about 2000 and see if the timing mark moves, it should, then let go of the throttle and see where and how it falls back to the idle speed position. A bad timing chain will stretch and give off-mark timing readings. Also, a bad lower bearing in the distributor shaft will cause the timing to float off the mark. The timing light will show the slop in a timing chain as the timing mark will jump around and not rise or fall smoothly under quick acceleration or deceleration. Black smoke is an indication of unburned fuel, which could be the result of a mechanical issue as I described above, but more than likely is a result of a primary ignition system problem, such as a bad plug or coil wire, distributor cap, rotor, or plugs. You can check the ohm of each plug wire, but if it changes dramatically when the engine is cold to when it is hot it is time to change the wires. Is it possible you are getting moisture dripping on your wires or distributor cap? Either condensation, saltwater, fresh water from washing down your boat, or spray from a loose clamp or hose fitting?

kwinters · Post by **kwinters** » Tue Sep 08, 2009 2:44 pm

Thanks for all the responses. She is still on the hill waiting for the new fuel tank. As soon as we can get her back in the water in will report on what it takes to fix her. Miss B, the wire issue is interesting and something I had not thought about. I had a shaft seal going bad spraying salt water on the fromt of the engine. I kept up with cleaning but the wires on the front four cylinders have had to see a lot of salt. We were in the process of sea trialing after replacing the wires and checking the timing when the fuel leak exposed itself so it has only idled to the the Ways to pull out and get the fuel out. I will also pass on the fuel findings if I get any. This tank has always used pure gas from the same marina most of the pst few years. I have seen something like a varnish inside the intake when rebuilding the carbs a couple of summers ago but nothing like this "Black Goop" some of you are describing. Any photos of a raycor or fuel tank would be interesting. My pickups when pulled out of the tan were all clean and just looked like old brass.

otf · Post by **otf** » Wed Sep 09, 2009 5:10 pm

kwinters, I rebuilt my motors that had sat prior to my purchase and the "black goop" problem. Goop isn't the right word, more of a black plastic coating on the inside of all the intake parts. There was nothing soft about it, maybe chip it off (like plastic). I kick myself, but never took any pictures prior to machining the heads and cleaning the intake. Nothing noticeable in the fuel system, prior to the engine, the heat of the intake definetly seperated it out. With your wire problems, sounds like that is probably it. Good luck!

kwinters · Post by **kwinters** » Sun Nov 22, 2009 11:12 am

OK. I back on this issue with all new fuel tank and any part that goes with it. I have 17 psi vacuum at 900 rpm. Slight flutter maybe half a psi at that point. Raise engine rpm up to 1300 rpm no load and it will kick up to 1600 without advancing the throttle. You have to back down on throttle to get it back to 1300 or so and as you ease up from there it will advvance on its own 300 or 400 rpm. The slight rough idle goes away as well as soon as the rpm advances up. Under load both engines seem to have the same power up to 2800 prm. You can then gag the one engine and she will go right up to 34 or 3500. You can do the same to the problem engine and she will struggle to get up there. There is a large power difference in the two. Tank,new. Filters,new. Fuel pump, new. Carb, new. Coil, new. Relay, new. Distributor, new. Wires,new. I am having issues with setting the timing as the information from marine power is skethcy or at least mot clear. Initial timing set at 12. total timing 30 at 4000. Wish I could get there again. Anyone can offer any suggestions would be helpful. I read a old post on marine power issues that a guy fought this problem for 6 years.

Gunny · Post by **Gunny** » Mon Jul 19, 2010 10:56 am

No mention of your compression readings?

bluelabel · Post by **bluelabel** » Fri Aug 27, 2010 9:28 am

check your fuel line, mine had air in it, replaced line and added bigger pumps, runs perfect, before that rough idle and shuts down alot

kwinters · Post by **kwinters** » Sun Dec 05, 2010 4:43 pm

We can put a end to this topic. When we replaced the Carb we used the thick nylon/plastic gaskets. They have 4 hard rubber sleeves that go into the gasket where the bolts go thru. Finally got a stethascope (sorry about the spelling) at auto zone and put on a small peice of hose that was long enough to reach around the entire intake manifold and carb area. Took about 2 seconds to hear that this gasket although new was leaking line a sive at the secondary base area. Put on the standard thin gasket that came with the carb and it has run for a year like a champ. I did have that engine overheat badly when first bought. I am thinking that the intake may have warped from all the heat but all good now.