75 HP Mariner Trouble

[cthornbury]

URGENT<br /><br />Having Trouble with 1988 Mariner 75hp when putting in gear. Can run out of water in gear and out of gear great! but when you put boat in water and try to put boat in gear it will die. I have cleaned carbs including under welch plugs. Motor has new spark plugs. I Have cleaned entire fuel system and relaced every line with new lines. Also New gas tank and Fuel Pump. Have checked compression(OK) and spark while under load. When you try to run motor in the water you can use sray bottle and sqirt fuel in lower carb and it will go and gear and run as long as you keep sqirting fuel in them. PLEASE HELP>

 

[roscoe]

Re: 75 HP Mariner Trouble

What is "compression ok"?

 

[cthornbury]

Re: 75 HP Mariner Trouble

Checked the compression on each cylinder and the compression on each clinder was within operational range.

 

[cthornbury]

Re: 75 HP Mariner Trouble

OK just had the carbs rebuilt per recommendation of local marine shop. The motor runs better than ever out of the water. Soon as you are in the water, falls flat on its face.

 

[dilligafda]

Re: 75 HP Mariner Trouble

This is a 1988 75hp 4 cylinder, correct? I had a 115 6 cylinder that acted exactly the same as you describe. I tore it down after checking all the components on the outside and found the seals on the reed blocks between the cylinders to be worn out. There is a multiple "V" groove machined into the reed block that is around the crankshaft and seals the cylinders from each other. when the engine is idling, there is enough fuel in the cylinder to hold the seal, when there is a load on the engine, the engine requires more fuel and pulls a little more vaccuum. This in turn draws that fuel out of the seal and a loss of aitflow through the reeds and therefore, a loss of fuel and the engine dies. Unfortunately, a complete teardown and reed block replacement is the only way to locate/repair the condition.

 

[Gold Bear]

Re: 75 HP Mariner Trouble

clarence t <br /> <br />When the engine is in the water there is more back-pressure on the exhaust. This affects the flow of air / fuel mixture. <br /><br />Your carb mixture screws are set to lean.<br /><br />Turn the carb mixture screws out about 1/4 to 1/2 turn and the engine should idle just fine in the water.<br /><br />Good Luck,<br /><br />Gold Bear

 

[cthornbury]

Re: 75 HP Mariner Trouble

This is a 4 cyl motor. Where are the reed blocks located on the motor and what are the costs associated with replacing them. Is it something that I could do with the proper tools or is it something that would have to be done by a marine tech.

 

[Mikael-Block]

Re: 75 HP Mariner Trouble

hi Clarence<br />Do what Gold Bear says, a hole lot easier than<br />checking reeds..<br />Allso check if all plugs are fireing.<br />I have a 1984 75 HP Marina, that had a bad switchbox, otherwise is a great engine.<br /><br />mikael