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Fuel or ignition problem

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fiveoclocksomewhere

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"1987 340 searay sundancer wit

"1987 340 searay sundancer with 350 crusaders/velvet drive trans.1000hrs.

first use of the day boat will plain and run fine.stop for 10min or 5hrs.

restarts fine,idles good.starboard engine will not go above 2800rpm on next plaining attempt.some times after a period of time engine will catch up and equal out.if you push the throttle all the way ahead it will come up to 3000 max.once thisyear developed miss at 3400rpm.stopped and idled boat for a few miniute and boat came back on plain and ran fine.i had this problam 2 years ago and adjusted the points and timimg and all was good.the boat will also feel like it is missing and surging at 1500-1800rpm.what i have done.

new points and cap,reset timing to 10 deg.
check and lube springs and weighs in distributer(there is rust on weighs and spring but are working)i have checked with timing light to confirm advance of upto 28deg. when accelerating engine.are they sticking when engine warms up??
swop coils from other engine.
replaced fuel filters in carb and water/fuel seperates inline.very small amount of dirt in filter in carb.
check anti siphon valve.(missing)???
before i go and spend more time and money i though i would see what you guy's thought as you always seem to have great advise.
i am looking into ungrading to electronic ignition this spring as this will eliminate any distributer or spark plug wire issues.i will also be replacing the spark plugs and fuel filters again.any thoughts or similar experiences."
 
First to go should be the igni

First to go should be the ignition wires.

Question: Is your fuel filter before or after your fuel pump? Your problem is typical of fuel starvation caused by putting a fine fuel filter before the pump--they should go AFTER the pump. Coarse filters and separators only should be located before the pump.

Jeff
 
"Jeff.

there was a stone ty

"Jeff.

there was a stone type or ceramic filter located in the carb where the feed line bolts to it.i switched this on both engines two years ago to a plastic type filter.it is locted after the pump.i have also updated the old cartridge style filter that was full of rust to a oil filter style filter that is located before the pump also two years ago.the lower rpm miss and surge seems like a electical break down and plan on upgrading to electronic ignition with wires and plugs, but i am concerned about the lack of higher rpm.i may have two problems here??it seems odd that it works fine the first go of the day and then starts to cause problems."
 
Sounds like fuel starvation to

Sounds like fuel starvation to me also. Might have something to do with a warm engine compartment vs. a cold one.

I had a similiar problem with loosing rpm after the engine warmed up. Found a kink in the intake hose to the fuel pump. When the engine compartment got warm the rubber hose would get soft and collapse at the kink.

My solution was to remove all that run of rubber hose and replumb the gasoline delivery system.

Just a thought.

Chuck Hanson
 
"Mike,

What do you mean by

"Mike,

What do you mean by "check anti siphon valve.(missing)??? " I had a similar problem caused by a dirty antisyphon valve, which was found after replacing the fuel pump, all filters, and doing a complete tune up. The cheapest and easiest job of all corrected the problem. See attached photo for location of the valve on top of the fuel tank.

Erich
374875.jpg
anti-syphon valve
 
Have you pulled this conncet a

Have you pulled this conncet apart to see if the anti-siphon valve has been removed? Hard to tell otherwise.

Jeff
 
"hi guy's.i pulled the val

"hi guy's.i pulled the valve apart two replace it and there was no ball in the valve.looked like it had been knocked out or removed??i am starting to believe this was a problem the previous owner has faced as well.i have owned the boat for 4 years and have had this problem on and off.the missing anti siphon valve leads me to believe the prevoius owner may have been trying to fix this on his own.the boat had sat for two years before i bought it from a guy who had purchased it and had a ton of work done on it before his wife decided that boating and the new baby were not going to work.he had a complete tune up done as well as had the carbs rebuilt.like you said erich,fixing the problem is the best idea vs throwing parts at it and hoping.thats why i am inquiring with you guy's.i have put approx. 300hrs on it since i have bought it and a tune up is do anyway.not sure that will fix the problem but will help in the elimination of suspects.when this started the first year i had the boat the engine would also fade out on plain,replacing dirty fuel filters fixed that problem but i still have the other issue.i am also wondering if there is dirt in the carb and after running for a peroid of time it sucks iin the dirt.the other thought is what about dirt in the tank plugging up the filter in the pick up.(i assume there is one)??

mike"
 
"At this point, I would rig a

"At this point, I would rig a temporary fuel pressure gauge between the fuel pump and the carb. I'd use A1 hose, barb fittings and clamps. If you see 5 psi during the time of the slowdown, it will eliminated a great number of unknowns."
 
5psi being normal fuel presure

5psi being normal fuel presure?if less than 5 start with fuel pump and work my way back to the tank.the fuel pumps on the boat are still painted in the crusader blue.would a pump last 23 years and if so why would it only fail under the conditions i described.

thanks to all for the input as most of these kinds of fixes come from many ideas and logical thinking.at the end of the day it saves us all a ton of $$$.saved money goes straight to the fuel tank and more days of enjoyeable boating.

mike
 
"Mike, you would be surprised

"Mike, you would be surprised at the logic used to repair some boats. My personal favorite is the BFH.....Good Luck"
 
"Mike:

those pumps will las

"Mike:

those pumps will last a long time. that said, I'd replace replace with quality replacement units if they won't provide at least four pounds of pressure consistently. If your budget permits, you may want to have the spares on hand as they likely don't have too much service life remaining.

It is also very possible that the bottom of the carbs' float bowls have some of that fine rust accumuation. those old sintered bronze filters are relatively coarse and won't stop those fine particles. the newer screen types will pass even larger particles. This stuff will move around and cause intermittent issues. Easily removed by servicing the float bowls."
 
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