Rough running engine Merc 228 hp

[frameman0]

Well, Im at the end of my rope and saw this site and figured, why not.<br />I have a 1978 22' Thompson with a Merc 228HP (305) V8. It has run well for years untill last season. The initial failure mode was a bogging down or a lack of power as you gave it gas. After this failure starts to show itself it will get worse until the boat has to be limped back to the dock I took it to a marina on lake erie that i do trust and after their inital attempts failed, they "shotgunned the probelm" amazingly at almost no cost. I will try to rememnber everything that has been tried.<br />- New Carberator<br />- New Distributor - complete<br />- New plugs (probably 8+ sets because the problem would somtimes go away (for a short time) after replacing them)<br />- Gas tank drained and filters(5+) replaced<br />- New spark plug wires<br />- Compression checked good<br />- Resistor wire checked (?) not sure about this and ut us still a concern to me<br /><br />There has been other stuff but I cant think of it right now. My thought for this season is electronic ignitors, is it possible that this will help, the mariana has advised me to put in a true electronic ignition at about $400.00 as opposed to just ignitors, my thought is that I had good luck with the ignitors in an old Starcraft I had. <br /> I could talk on and on about things that I have tried and thoughts I have on what it is, but Im putting this out here to see if anyone is interested helping work through this, if I cant get it going this season I will have to get rid of it, its been a good boat and a great engine for years, it has to be something that can be fixed.<br />Thanks

 

[Bondo]

Re: Rough running engine Merc 228 hp

At 1st glance it appears you have a Fuel Delivery Problem......<br />Seeing that you've already done the,- New Carberator,+ - Gas tank drained and filters(5+) replaced........<br />That leaves the,<br />Fuel tank pick-up assembley.....<br />Fuel Anti-Siphon Valve.....<br />Fuel Lines.....<br />Fuel Pump......<br /><br />The Easiest way to check this out is to Verify that you have 5psi Fuel Pressure At the Carb Inlet...... This Should be at All RPMs,+ Load conditions<br /><br />As to your Ignition Upgrade,<br />Start Searching ebay......<br />You'll be able to find a Complete ThunderBolt IV for a Reasonable Price if you Keep Looking....<br />The T-Bolt IV is about the Best Available.....

 

[frameman0]

Re: Rough running engine Merc 228 hp

Bondo, thanks for the reply. Is there any way that I, as a backyard mechanic, be able to check the pressure, the pickup and the pump etc. I have a manual but it doesnt have the tests requirements to do this. Is the electronic ignition you refer to a complete unit with distrib, coil etc, or an ignitors upgrade. Also, when the marina priced out the retrofit they said I would have to remove the resister wire and that it is extremely difficult to find, your thoughts?<br />Thanks for all your help

 

[fireship1]

Re: Rough running engine Merc 228 hp

Hello! Resistor wire does not have to be removed if you decide to go with the ignition upgrade. Just snip it off where it goes to the coil and tap any wire that you find in that area that is hot when the key is turned to the crank and run positions.Pull the pickup at the tank. there is a small filter that is at the end of the pickup that could be cloged with gunk. There is also an anti siphon valve that is fited to this pickup on the outside of the tank. Make sure this is not blocked off or clogged. Fuel should suck out and not be able to drain back. To check fuel pressure tee a fuel pressure gage into the carb inlet and attach the fuel line to it. Gage can be picked up at any auto parts store Autozone,Nappa etc..Also tru pulling the line that supplies fuel to the carb from the fuel pump. Connect a rubber hose and place in a container. Have someone crak the engine while you hold the hose in the container for a few seconds and see how much fuel you get. I know that there is a certin amount you should get by test standards in the service manual that I do not know offhand, but off the top of my head the jar should fill fairly quickly. If you want to be exact and can't find the test data ask some of the other guys here. They are MORE than knowledgeable about this kind of stuff! The ignition that Bondo refers to is a complete system made by Mercruiser. It is worry free and made for the marine environment. I myself have an ignitor ignition module upgrade in my boat. It was a snap to install and works great. It will also work with the standard coil and the resistor wire in place and connected. I hope this stuff helps you out.Don't give up! Keep posting,we'll try our best to help you figure it out! Good luck!

 

[Bondo]

Re: Rough running engine Merc 228 hp

Yep, Everything fireship1 says........<br />Except, I'd rather disconnect the resistor wire where it starts at the starter..... No Sense having a "Live" wire with No Where to go.....<br />Mercruiser came out with the ThunderBolt IV a year or two After your engine was built.... It's a Great, Nearly Bullet-Proof System.....

 

[Walt T]

Re: Rough running engine Merc 228 hp

This is not an ignition problem. Have the exhaust flappers been checked?