More 3GM30F Questions

Author Message   Kerry Allen Member Username: cascade_36 Post Number: 5 Registered: 06-2007 Posted on Monday, January 26, 2009 - 09:58 pm:    Hello all. It has been quite a while since I last posted. Unfortunately it was very tough to get to the boat in 2008. I finally made it in late Nov for an overnighter at which time my friend and I pulled the head and injectors off my 3GM30F. The reason was it was hard to start cold but ran great and started easy warm, I could see coolant stains where coolant had run out of the head gasket seal and down the port side of the engine, and when the engine was warming up it would pump air (not much) into the coolant overflow tank. I need to trust this engine and decided to open it up. Now I am ready to re-assemble it as the head has been ground flat, valves and seats ground, and the injectors (tips good, a little out of spec on the cracking pressure) cleaned and brought up to spec. I have my gasket set and a Yanmar maintenance manual. My question is that the manual calls out for lots of different gasket sealers (Threebond#4, etc) for the head gasket and others. I looked online and I suspect Threebond doesn't even make that series anymore. Question #1 = Do you recommend a gasket sealer at all on the head gasket? I thought head gaskets didn't need any unless the head was warped. #2 = If I do need various gasket sealers, locktights, and thread lubes, what do you recommend? The manual lists about six different compounds but I suspect I don't need quite that many. Can I just pick some up at a motorcycle shop or do I have to buy "Yanmar approved" stuff from a marine deisel shop? You guys have helped me in here before and any more advice you would be willing to give would be much appreciated. I plan on starting this motor in about a week with a little luck and help from my MarineEngine.com friends...... Thanks... Kerry   Ronald E Cairns Member Username: ron_cairns Post Number: 96 Registered: 12-2005 Posted on Monday, January 26, 2009 - 11:01 pm:    Hi Kerry, The head gasket goes on dry. For other gaskets you can get 3 bond at your Yanmar Dealer, some carry it and it is good stuff. I found that the bond for the air cooled 4 cyl.volkswagen engine worked well but I have not bought that stuff in eons. An good automotive supply shop will have a good compound. There are many heat range silicons but use sparingly. Too much may seperate and block oil and water passages. Take your time and think things through. Check your con rods, make sure one has not compressed if any water got into the cylingers. A short rod will cause hard start. The machine shop can do it. But since you have the head off,use a depth guage, make sure all TDC to the block/head face are equal. Your manual should cover this, Best of luck and enjoy...Ron   Kerry Allen Member Username: cascade_36 Post Number: 6 Registered: 06-2007 Posted on Monday, January 26, 2009 - 11:25 pm:    Thanks once again Ron. I really appreciate it. I hadn't thought to check the rods but I will do it before I go any further. The head shop said the valves and guides looked good. The cylinder walls also looked pretty good. I am begining to think this was actually a low time engine that was put together badly. The claim was that it was professionally rebuilt but that doesn't seem likely. I found one of the studs on the exhaust cooling unit had a cross threaded fine nut on it instead of a course threaded one. I have the new stud and nut. I wasn't planning on pulling the pistons and honing and re-ringing. Do you think I am making a mistake by not doing that?   Ronald E Cairns Member Username: ron_cairns Post Number: 97 Registered: 12-2005 Posted on Tuesday, January 27, 2009 - 04:23 pm:    Hi Kerry, Can you see a cross hatch on the cylinder walls from the honing of the cylinders? If the cylinders and smooth like glass, I would pull the pistons, check & hone the cylinders and install "new rings" After the rods have been sized assemble and take out for sea trial. These GM series engines are designed to run at 3600 rpm full throttle. That will tell you the prop is sized for the boat. After that run this engine at 3000 rpm. This will give you the best torque and fuel economy. Lower rpm will not work the engine and glaze the cylinders. Remember to lock the gear in reverse when under sail with no power. This is a great engine and will give you years of service. Since you do not know the history of this engine, do it up right. Over the years I have seen some wide and wonderfull overhauls done by so called experts. Adjust valves once a year at .008 and change the oil. Enjoy and happy sailing. Regards Ron   Kerry Allen Member Username: cascade_36 Post Number: 7 Registered: 06-2007 Posted on Tuesday, January 27, 2009 - 06:21 pm:    I will happily take your advice Ron. You've been a great help. I hope I get the chance to buy you a beer or three someday. Kerry

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