Need a little help with a Merc OB cooling system question

[MH Hawker]

Re: Need a little help with a Merc OB cooling system question

Dont get frustrated with it its all part of a learning curb that comes along with any new boat and these guys know their stuff.

Take several pictures of the back of the motor ( left, right, and center ) and the controller its a lot easier for them to help.

 

[tumblebug1949]

Re: Need a little help with a Merc OB cooling system question

Thanks MH,

I would have already taken the pictures but it is stored in my barn and there is very little light where the engine is at. I will try to take a light out to see if it is bright enough to get some pictures. The swivel plate is where the tag is that I can not read. The only part of the tag that is faded out is the top block which is the number I need. There is a fairly large tag on top of the cylinder block right behind the fly wheel. It has some printed numbers on it and gives a motor family number what ever that is. I have read in several places about the number stamped into the freeze plug on the starboard side of the block. That should be easy to find but I have not found it yet.

This all started because I could not find where the tell tale outlet was at. It has to be on the back of the lower cowling on the starboard side. It is not there so I am thinking it does not have one and the water exits through the exhaust. I have read somewhere about adding a tell tale and will give that some serious thought. I do not trust a gauge.

If it were not for wanting to get the right parts like an impeller, I would not care what the serial number or model number was.

Thanks Tom

 

[Maxz695]

Re: Need a little help with a Merc OB cooling system question

View attachment 180536This is a 40 HP 2 cylinder 2 stroke 1979 swivel arm. There should be a little metal tag on the opposite side with the serial number on it. It is slightly indented into the metal and if unreadable try to very lightly use fine steel wool to romve the outter paint which should reveal the nimbers more clearly. The number on this 79 motor started with 56626XX Maybe you can figure the later models and get an approximate clue on which diagram fits with you engine best. Being a tracker motor this may o may not help you but have a look anyway

 

[tumblebug1949]

Re: Need a little help with a Merc OB cooling system question

Thanks Maxz695,

That is a spot that I have not looked at at all. I will check it tomorrow. I really appreciate everyone trying to help me figure this out. I think there is a good chance this will answer my question. The motor appears to be in good condition but needs some cleaning. The inside of the lower cowling could use some soapy hot water to remove all the oil. I know the oil in the lower foot has been changed because the streaks of oil are still trailing out below the vent hole since it was not wiped off after the job. The last owner said he changed the gear oil at the end of each year. I want to change the impeller first chance I get. The prior owner said he doesn't think it has ever been changed. Knowing the model number will help there. Then, I want to get the idle rpm's set. I think it is idling way too slow. I also believe there is a tube that runs from the motor to the back of the water pressure gauge. I want to make sure it is functioning correctly.

I appreciate the help
Tom

 

[oldman570]

Re: Need a little help with a Merc OB cooling system question

If the boat is equipted with a pressure gauge and it is working, you should get around 3 or 4 LBS at idle and up to 18 LBS at WOT if the impeller is new or in good shape. If the tube from the gauge to the motor goes to the head water jacket,or the exhaust platecover, then it could be that when the setup of the unit was done,where the tell tail was/should be is where the gauge has been installed. If you want a tell tail you can use a short 1/8" pipe nipple, tee and hose barb fitting and add the tell tail at that location. The gauge will probly read some lower than it should but not if the hose for the tail tail is restricted as it should be. Restictring the hose can be done with a smaller hose placed inside of the tell tail hose for a few inches where it goes thru the lower cowling and can/should be tight in the cowling. I use a short pice of small clear gass hose for the restrictor part. If you cannot find a full SR# for the motor you can take the old impeller to a Merc dealer in your area and he should be able to match it to the one you need and give you a good idea as to what years of motors that yours could be. JMO
Oldman570

 

[Maxz695]

Re: Need a little help with a Merc OB cooling system question

When setting the idle Do not adjust the low idle stop but use the low idle timing screw instead. The linc and sync reuires the carb be just touching or slightly before touching the cam to the throttle lever on the carb. Using the low idle timing will raise the engine RPM and would be the correct way to bring up the RPMS nessecary to get a good idle in gear. JMO

 

[tumblebug1949]

Re: Need a little help with a Merc OB cooling system question

Thanks Mazx695 and Oldman570,

I will keep the information about adding the tell tale hose and I appreciate the information on restricting the outlet to maintain a good reading on the water pressure gauge. When I had it idling the other day in a trash can full of water, I should have crawled in under the cover and looked at the gauge to see what it was reading. I am not used to having one and did not think about since my main purpose was to get Seafoam circulated through the motor. There are two elbows on the starboard side that go into the motor and then disappear around the front of the block. Probably going to the gauge. I will check more on that when the time comes and when I have it out of the dark barn that it is in. Right now it is all flashlights and reading glasses which make it difficult.

Maxz695, I raised the motor as high as it would go and of course had to squat under it and try to look straight up to look for numbers. First I saw raised numbers on the round tube it pivots on. Those being raised numbers have to be a part number because they would need to be in the mold when it was made. I figure I am looking for numbers that are stamped into the metal. There are several flat surfaces under there but I could not see any numbers on the easy to see surface. I did see some numbers (3) that were up in a rectangular indention. Indented to add strength to the bracket. As you had said, I might need steel wool or something to get it to where I can read it all. It is a real pain to be under it and twist around and look straight up. !0 years ago, maybe but now, it is not an easy position to be in. I will wait for it to warm up slightly and than grab a bale of straw I have there in the barn to give me a bench to lay on while looking up. Hope I don't make it too comfortable, I may just go to sleep. I will probably do what Oldman570 said and go ahead and get the impeller out and take it to the shop to get a new one. I will also pay close attention to where I adjust the idle at. Probably take some pictures first when I can get it out in the daylight. Or, I just may support my local Mercury shop and have then test the engine and adjust it.

I did note that there is not an air filter no the carb. It is a new carb that the seller just put on and I have the old one also. Is this normal or do I need to get a breather and filter for it?

Getting help on this is great. I sure wish it were warmer out in Indiana so I could spend more time outside.

Thanks for the information.

Tom

 

[Maxz695]

Re: Need a little help with a Merc OB cooling system question

No filter is required