Rodchester Carb freezing issues anyone else with these issues-gctid390227

[Guest]

Hey guys I have a 2159 trophy, it had a 305 in it and I changed it out for a fresh 350 it runs great I rebuilt the carb as well it has propane intake gaskets with the bypass closed because I thought it was heat issues but am thinking it is possibly freezing up

I also changed out the carb for another that was running on a 350 with out issues

The problem is I warm up the motor and head out it runs great for 20-30 min then causing at say 3100 rpm it starts to loose rpm with nothing above the current throttle position

I shut it down for 2-5 min and good to go for another 8-10 min then the same thing

I installed an electric fuel pump thinking it was a fuel delivery problem but no doesn't seem so

Base of the carb is cold but I don't see any frost or anything

The weekend before it did it only once crushing at 3100 so after a 5min shut down I crused at 3400 with out further issues

I know with certain humidity it cases issues

I'm not at sea level but the weather is warm

Any imput would be appreciated

Thanks Tfl

[Guest]

I'm not really sure about the reference to propane gaskets...?

I do hope the 350 carb you got was for a boat?? They are different than automotive carbs.

Just an opinoin, but I doubt you have carb freezing. You may very well have fuel starvation.

There are other things that can cause fuel starvation besides a bad pump, like a bad gas tank vent. A vacuum builds and the pump can't draw fuel anymore. Or, it could be a filter not screwed on tight enough causing a vacuum leak before the fuel pump.

When it dies, pull the spark arrestor and have a buddy stroke the throttle to max...do you see fuel squirt in? If you do, then it's not fuel (Think ignition, possibly overheating coil). If you don't get the squirt it's definately fuel.

Chay

[Guest]

Thanks chay

I had some problems with my omc ignition I change it over to mercruiser

The carb is a marine carb as well another rodchester

I did look down the carb and had the throttle opened and the accelerator pump do squirt gas as it should but the gas hit the bottom of the manifold and sizzled so I thought maybe too much carb heat and installed a set of propane gaskets which block the exhaust crossover in the manifold (it's not a vortex 350) old school meant for a carb

I am still wondering about fuel pressure thinking of putting in a pressure gauge to double check

Possibly

[2850Bounty]

Moisture in the air is what freezes from the refrigeration principle when gasses from a higher pressure environment rapidly escape into lower pressure environment. The fuel itself will not freeze, but any moisture in the air may!

I doubt that this is your problem.

I'm not familiar with the Propane system, nor what the base gasket difference is. However, I think that you'll want to use the correct carburetor base gasket.

You say that you changed over to the Merc ignition. Just what ignition is this?

If EST (the Merc TB system) are you certain that you understand the BASE timing procedure?

EST = electronic spark timing. An electronic ignition module does the actual progressive spark advance.

Ditto Chay on the Ignition Coil.

If this is the Merc TB system, it requires a specific type coil. Do NOT substitute!

Ignition Timing:

As with any Marine Engine, we should not only be setting BASE advance, but we should be verifying the progressive advance, and looking to see where TA occurs.

This is nothing to mess around with, or go at hap-hazardly!

I'm not suggesting that this IS your problem, but I am suggesting that you verify this as per your OEM specs, and as per your engine build!

Do this, and it may be found to be the issue, or it can be checked off of your P of E list.

You also say that this occurs after 20-30 minutes running, and at 3.1K rpm.

20-30 minutes ensures full engine temperature.

Since it makes it past 20 minutes, I can't quite see a fuel starvation issue.

If 3.1K rpm is not at planing attitude, you are loading the engine heavily. Loading the engine heavily will raise cylinder temperatures. High cylinder temperatures may cause detonation, or put you very near detonation. Throw in incorrect ignition timing..... and you have a recipe for engine damage!

If the cylinder temperatures are nearing the extreme side, and if the engine is just beginning to detonate, you may see a reduction in RPM.

This is very dangerous if this is what's happening.

(see Ignition Timing note above!)

NOTE re; the electric fuel pump:

An electric fuel pump used in an enclosed engine bay must incorporate a low oil pressure shut-down switch or circuit.

This is a USCG regulation.

This also requires a means of exciting the fuel pump prior to oil pressure during cranking.

More on that later if interested.

.

[Guest]

Thanks 2850 bounty

The ignition is the merc electronic max advance I believe was 21 degrees I'll have to verify as well as the coil I guess

The eng is warmed up before taking off I usually idle it for at least another 15-20 min before taking off and I did verify my gauge with a temp gun it's pretty close

The boat comes off step at about 2800rpm if I have her trimmed right so I don't believe 3100 is over loaded it does 24mph at 3100 and sounds good I need to in stall a vaccum gauge as well just curious here best economy is for crusing

As for fuel pump I did install a pressure switch which activates a relay to the pump with a extra wire running from the dash to a button to send power to the relay just to send presure to the carb but only need to use it for first startup of the year (i like to run the carb out of fuel before storage) a little hillbilly but it seems to work ok Lol

I am interested in the proper set

I'm in norther B.C. Canada

The propane gaskets I speak of mearlly have a plate blocking the exhaust passage that goes through the manifold under the carb from one bank to the other As propane does not require the heat under the mixer newer vortex blocks are fuel injected and don't even have the passage cast into the heads

As for freezing ya it's just like you said the pressure drop in the right humitity causes it to freeze we have problems with our two stroke inboard sportjets doing that up here at times on the rivers

I have never had the fuel tank out and was wondering of something is wrong with the pick up

I sucked it out best I could and change all fuel lines and I did check the vent also it's free and clear

It was a very consistant problem last weekend

I'm just asking for I'm put because I was going to head to the coast for a fishing trip in July lol

I thought I checked all the obvious things a couple times looking for clues as to why it's doing it so any imput is appreciated lol

[iceclimber]

Simple first, does your fuel pickup have a check valve ?

[Guest]

I'll have to check for one

Are you referring to the anti sifoning one

[Guest]

I think at this point I would try an auxilliary tank. Connect your kicker tank if you have one, to isolate tank side issues from the pump/carb side.

I reread your original post and it sounds like either ignition retard or fuel issues.

Do you get knock or ping before it dies off (Sign of lean afr)?

Chay

[Guest]

Hey guys thanks for the help

I took her out with a fuel pressure gauge installed and found at idle 6psi cruse was 5 and wot 4

At cruse for 15 min it had dropped off to 0 then started acting up.

I rechecked all the filters carb,water separator and inlet screen on pump and found a small amount of particals.

So I did what cfoss mentioned and had brought along a 5gal can and hooked her up and it had 9psi at idle and 7.5 at cruse and wot

I was wondering about the anti siphoning valve and where is it located right in the tank?

And is there any kind of pick up filter in there as well

Thanks Tfl

[Guest]

On my boat the anti-syphon is located at the output of the tank (Just after the on/off valve if there is one). It looks like a slightly larger brass barrell.

Like this:

http://www.iboats.com/Anti-Siphon-Va...view_id.392108

Found this:

http://www.marinemechanic.com/asof-8-29/antsiphon.htm

It might help you.

Are you absolutely sure your fuel tank vent is ok?

Sure sounds like your fuel pump is drawing a vaccuum on the tank.

Did you try to open your fuel inlet cover (where you pump gas in) and listen for a suction sound indicating a vacuum (Just after the fuel pressure goes to 0)?

It could also be a weird blockage. I had one in my 17' K+C once. What had happened was a guy had used silicone to seal a gas tank fitting (on/off valve). When he did this he created a flap of silicone which would sometimes act as a one-way valve over the end of the fitting. It died out every 10 minutes or so. Very hard to find. You may hove to do what i did, and disassemble the whole feed side of the fuel system and go through it component by componenet until you find the smoking gun.

Anyway, I got the boat cheap (He obviously couldn't find the problem and just wanted to dump it!)!!!

Chay

[Guest]

Thanks

Chay for the info

I'll double check the vent and the anti siphon valve

I'm stuck working out in camp and was hoping to check it during

the week here

Was planning a trip for the weekend lol