Why is there a hole in my piston?

[George Serumgard]

I'm rebuilding a US Marine Force 50HP and have the following questions:<br /><br />Why would one piston Fry, and the other look like new?<br /><br />Do I need to replace the pistons as a set?<br /><br />Molton aluminum sprayed all over the inside of the engine, Do I need to install new bearings<br /><br />This engine ran great for many years, and I'm very impressed with the quality of the machining and engineering. It looks like a very robust, simple motor. Why does everyone say they are CRAP?<br /><br />What year is mine 507X8C 2120<br /><br />Thanks

 

[eurolarva]

Re: Why is there a hole in my piston?

The motor is 1988. Welcome to I boats. I see you are from golden valley. I am from Blaine. Nice to see if finally stopped raining. I own a chrysler so I cant help you on the rebuild. As to your question concerning the force POS theory. From what I heard is that force was an economy motor produced by Mercury. Short cuts were done in order to keep pricing down. I read the mercury posts and there are lots of problems with them as well. <br /><br />I am pretty sure you are going to have to replace those pistons as a set. What number is on the piston now. Hope they have not been bored out already.<br /><br />You are pretty close to Twin City Outboard. They should have everything you need to do the job.

 

[George Serumgard]

Re: Why is there a hole in my piston?

Thanks for the Advice Eurolarva.<br /><br />I brought the block and pistons into Hannay's (near broadway and central in Nordeast) and asked them to give me a shopping list of parts with the intension that I would put everything together.<br /><br />The mechanic explained that the rings must have a solid contact with the cylinder in order to desipate heat. If the cylinders get too out of round and the rings get too sticky heat builds up in the piston and they melt. That's how you can have on piston melt and the other look just fine.<br /><br />So, I need to have the cylinders bored. They want $120; I can get it done for $60 at Red Rooster. I'm interested to see what they want for the rest of the parts. <br /><br />What's the best place to buy stuff. You mentioned the place in Shakopee. Are they going to be cheaper than a place like Hannay's?

 

[eurolarva]

Re: Why is there a hole in my piston?

I had some bad experiences at TC outboard. Me personally would go with hannyes. They treated me pretty good when I was there. They wont work on my motor because their manuals dont go back to 1967. I read in some other posts that you should be able to just bore out the bad cylinder and not have to do all of them. If you have the manual maybe you could have red rooster do the machine work and you do the rebuild. I have never done this part so I am of little help. Here is an online place so you can see how reasonable the parts you are buying. <br /> piston and parts <br /><br />Good Luck

 

[DJ]

Re: Why is there a hole in my piston?

Maelstrom,<br /><br />The ring sticking theory is a good one. I believe your engine has a single carburetor, thus a foulded carb could not have caused it.<br /><br />The Force engines tend to run dirty, thus a decarb is nesessary on a timely basis. That is probably why your ring stuck.<br /><br />eurolarva,<br /><br />I used to live in Blaine. Southwest corner of Central Ave. and 99th Ave.

 

[George Serumgard]

Re: Why is there a hole in my piston?

Yes DJ, this is a single carb engine. Can a better quality oil help to reduce the carbon build-up?<br /><br />When you talk about a "decarb" are you talking about using some chemical de-carbing system, or are you talking about pulling out pistons from time to time?<br /><br />Thanks for the Parts Link EuroLarva. I'll let you know how it all goes. <br /><br />Any additional advice is very much appreciated. Especially any of the typical trouble spots that I should be paying attention to.

 

[eurolarva]

Re: Why is there a hole in my piston?

decarb is described under fAQ section. It can be done in a couple of ways. The easiest comes in a spray can and is sprayed into the carb while motor is running then after it kills spray the rest of can into the cylinders and let sit for an hour or more then run the motor to burn the stuff out. My preference is to run every third tank of gas with seafoam mixed into the tank (this product is made in Minnesota. got to be good stuff) then clean plugs or replace them when they get fouled. I hear that synthetic oil burns cleaner and leaves less carbon deposits.

 

[DJ]

Re: Why is there a hole in my piston?

Decarb as in the process described here:<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=36;t=000016 <br /><br />Some say that synthetic oils reduce carbon.

 

[George Serumgard]

Re: Why is there a hole in my piston?

Thanks Guys,<br /><br />I'm familiar with the Seafoam products, and they work great.<br /><br />Sea Foam Sales also makes a product called "Bugs-B-Gone" that I found works great for getting bugs and other "$h1%" off boats and windsheilds.<br /><br />Check it out!<br /><br />Thanks