79 Merc 70 hp - Hard to start

[tipit008]

My 79 70 Hp Merc has a hard time starting. Good thing I have a strong battery...

It turns and turns, sometimes not starting on the first or second tries. After it's turned with the starter only for about 15-20 seconds... I stop, not to burn the starter. Sort of reminds me of an old Ford I once had...

Once it starts, it runs relatively o.k. It does stall once in a while at low idle.

I know this may be a number of things... can anyone make suggestions as to where to start to look??

Thanks.

Marc P.

 

[TommyA]

Re: 79 Merc 70 hp - Hard to start

The first thing that comes to mind here is there is a lack of fuel getting to the engine. This could be caused by filters, fuel pump inop, dirty carburetors or carbon crudded engine. Look over in the FAQ section on Outboards and you will find the instructions of checking all listed above. I believe with the age of your engine I would start with De-carbonizing. This doesn't require any disassembly and should be done on a regular basis anyway. If that doesn't solve the problem then move to cleaning the carburetors next. Rebuilding the fuel pump is fairly simple and parts are generally less than $10. Start with those items and then get back to the forum with your results. There are plenty of ideas and helpful tips everyone will gladly offer after you cover the normal maintenance items.

 

[tipit008]

Re: 79 Merc 70 hp - Hard to start

Thanks for the tips.

Sorry, but I'm a newbie and trying to find something in the FAQ is a bit daunting. It's actually not a FAQ, but more of a listing of all past posts according to subjects. They don't even have a listing for a 70 Hp Merc, only 75hp which is not what I have.

How do I de-carbonize the engine? Did a search with this term and it returned nothing.

Thanks.

Marc P.

 

[TommyA]

Re: 79 Merc 70 hp - Hard to start

Most of the listings are for general engine maintenance and are not model specific so they will work for any engine. Carb cleaning is the first listed and will work for Evenrude, Johnson, Mecury, and so on. Read the direction through till you get a good understanding of what the task at hand is. Then get out and work on your engine. The Engine De-carbing directions are listed on the second page of the Posts. When you open the FAQ section you will see where you are on page one of two pages. Here is a link.

http://forums.iboats.com/forumdisplay.php?f=31&order=desc&page=2

 

[tipit008]

Re: 79 Merc 70 hp - Hard to start

Thanks for the info. I just realized that there are TWO FAQ, one in the blue bar at the top, and one at the top of the forum subjects... which is much more useful and easy to find stuff in.

Again, thanks.

I'll de-carbonize the engine and come back here to give the results.

Marc P.

 

[dlplost]

Re: 79 Merc 70 hp - Hard to start

idle mixture is too lean...

 

[tipit008]

Re: 79 Merc 70 hp - Hard to start

O.k., here's how my engine is now after putting into application some of the suggestions recieved here.

I've done the de-cabonizing procedure, and, yes, it did spew out a lot of thick blue smoke.

Haven't yet changed the spark plugs, but will do that soon.

On the weekend, used the boat on a big lake. Did shuttle service for about a dozen people between a boat ramp and a campsite about 7km (5 miles) away.

Since I've done the de-carbonizing, the boat starts *a bit* quicker, instead of sometimes turning for over two minutes before she starts, it now takes rarely more than 15 to 30 seconds to start the motor... which is still far from perfect.

What does happen and puzzles me a bit is this:
After running the boat for a while, it acts as if it's running out of gas, but the tank's still half full. I pump the (what do you call that thing....???) pear-shaped balloon along the gas line to pump some gas from the tank to the motor...??? and, at this point, it is very soft. When it gets hard again, the motor starts fairly easilly and goes on for another little while. What is funny is that, twice, the motor began to do this (stall), just as I was either getting to the campsite or back to the boat ramp and people thought I was just slowing down the motor..., but the motor just stalled right at the end of the trip.

Could there be something in the motor preventing the gas (or enough gas) from getting to the carburators?? Could it be a clogged gas line filter?? Is there a gas pump on these motors??

Thanks for any advice or suggestions.

Marc P.

 

[jeff_smith_0423]

Re: 79 Merc 70 hp - Hard to start

Rebuild fuel pump and check all of the fuel lines and filters. Your motor is starving for fuel.

The first thing that comes to mind here is there is a lack of fuel getting to the engine. This could be caused by filters, fuel pump inop, dirty carburetors or carbon crudded engine. Look over in the FAQ section on Outboards and you will find the instructions of checking all listed above. I believe with the age of your engine I would start with De-carbonizing. This doesn't require any disassembly and should be done on a regular basis anyway. If that doesn't solve the problem then move to cleaning the carburetors next. Rebuilding the fuel pump is fairly simple and parts are generally less than $10. Start with those items and then get back to the forum with your results. There are plenty of ideas and helpful tips everyone will gladly offer after you cover the normal maintenance items.

 

[tipit008]

Re: 79 Merc 70 hp - Hard to start

Hi,

I've now replaced the fuel pump (found a new one, not too expensive), the fuel line hoses that were cracked, but not the fuel filter that was very clean so no need to replace.

I've also replaced the spark plugs. When I took the old ones out, there were full of a black sticky muck,

maybe a remnant of the decarbonizing procedure ? ?

Any thoughts on this ? ?

I'm using it again this weekend and we'll see.

Will get back here with news.

Thanks for all the good suggestions.

Marc P.

 

[TommyA]

Re: 79 Merc 70 hp - Hard to start

That sticky muck was the carbon build-up inside your engine. When you did the de-carb it broke it loose. I believe you should have a better running engine now with all you have done. Try starting it on muffs and I'll bet it starts quicker.