Mercruiser 888 (Ford 302) Stalls at 3000 rpms

So I purchased an 1973 Century Raven with a Mercruiser 888 I/O (Ford 302) and ran fine the first few outings. Soon after it started stalling around 30 seconds after getting on plane around 3000 rpms. It was hard to start but eventually stalled again. We creeped back to the dock around 1000rpms, but slowly they started to drop and soon sputter and stall when it got down to 800 rpm. Would not start unless left for 10 mins. Again, and again I followed this till we got back to the dock. The next day, I tried to trouble shoot the problem, but it would not start at all. I thought that it was a fuel problem, but can easily see gas spray into the carb. and also tried my trusty can of starter fluid. I gave the boat a full tune-up, replacing plugs, wires, coil, distributor cap, points, condesor, fuel filter/water seperator, battery and everything else I could think of. Re-tuned the carb., and filled it with fresh fuel. Still, same problem. The carb is a 2 barrel marine carb from holley and looks like it was replaced not too long ago. I dont know what else to check. I tried the many safety kill switches but they all seem to operate correctly. I have heard of this problem before with other boaters on this forum but have yet to really find a solution, others believe it could be a bad tach., timing advance is offset, fuel pump, and breather valve. I am really unfamiliar with these and could use some advice. Please help. Thanks!

 

Not sure why a bad tach would cause the engine to run poorly. Fuel pump not up to specs? Fuel tank vent line plugged? Sucking air into fuel system. Fuel tank pick up tube getting blocked by crud in the bottom of the tank or positioned wrong. Vapor lock caused by a fuel line getting too hot. If you have ruled out the spark issue by replacing everything then it must be in the fuel system somewhere.

 

Is there power getting to the coil? Try a jumper wire directly from the battery

 

Bad Tacho can definately stop the engine as its conected to the points side of the coil on that engine.
There is a filter in the fuel line where it goes into the carb, but I assume was cleaned if the carb was replaced.
If water went through the fuel system the fuel pump can corrode as it has a low spot that will hold the water.
The rotor button can also play up on those. I have replaced a few with problems as its not something you normally see.
The ignition does have a ballast resistor block but it is a wire built into the wiring loom on the engine, so a good test ( as mentioned above) is to jump the power to a B+ and see if it helps.

 

Got exactly the same problem .

I installed a new fuel pump , water seperator and new coil and still stalls a few seconds after planening sometimes it will start immediately and run again for a minute or two and then stalls again but sometimes it won't start anymore until engine cools down and it will start again , idle is okay and starts very easy . I'm getting frustrated but I can't stop now because I had already put in too much money in this boat for it's value I got the boat cheap but I had the interior strip and redone , a new full top canvas , brought it to a boat shop to make it running , had the 888 outdrive tuned last fall and test run it in the lake with the boat mechanic that time everything looks to be fine before storing it this past winter and I was so excited launching it this summer and got a slip at the marina but then this stalling thing is always happening and it's just really very frustrating for me and money is tight and exceeded my budget . Today I'm going to change the fuel host from the main fuel tank going to the seperator but I don't think this will solve the problem a mechanic told me that sometimes when a fuel host is so old the diameter of the hole get's smaller when it get's hot and from the build of particles on the linening of the interior I don't know but right now any advice I will take it .

 

Take a hose or other fuel line, connect it to the engine's pump and a can of clean fuel.
Put the hose in the can until the bottom, have someone hold it upright and start the engine, which may take a while. Then make your test drive...
If the problems have disappeared, the cause must have been dirty fuel, a clogged fuel line, filter or separator. Should the problem persist, concentrate your efforts on the engine, like carb and fuel pump.

 

If your budget is tight, changing parts without troubleshooting is a bad idea. You are spending money on things that were not causing the problem. Try a test light connected to the purple wire at the coil. If the test light goes off when the engine dies, you may have a bad switch or connector. A gas can with clean fuel will also isolate a possible problem. Disconnecting the gray wire that goes to the tach is an easy way of testing it too.

 

Thank you CDK for your response , bypassing my main fuel tank is also one of the thing that I have in mind to do I just have to wait for calm water because right now it's quite rough here in lake Ontario and my boat is in one of the marina here in Toronto and it just feels good when you know someone reads your post and reply thank's again and I will do your advice .

 

Hi Gonzo you are very right I'm spending money on parts that is not causing the problem because I'm not really a mechanically incline person but I've also spend a lot of money in refutable boat shops here in Toronto before I stored the boat before winter expecting enjoying the boat with my family this summer but it did'nt happen . That's why I'm just trying my best now to fix it myself as much as I can like I bought a new fuel pump last week and change the coil last Sunday but still it did not solve the problem , I will do that test light but what switch and connector are you talking about sorry for my ignorance but I really appreciate your advice thank's again .

 

I had the same problem with my century. Replaced everything. Until this summer when I was told how stupid I was. 3 $ part fixed the problem. Common for the fuel tanks in these boats they have a check Valve on the outgoing fuel line. Replace it with one that doesnt have the spring and ball bearing and boom ! Problem solved. It the brass fitting on the top of the fuel tank.

 

The spring and ball, called the anti-siphon valve is an important safety feature and required by Law.