Mercruiser 4.3 Engine hard to cold start!

[bign1514]

Hello all, I've been reading here for awhile and always find the answers to my problems (thanks for providing the support). But, I can't seem to find the answer to my one big problem after doing lots of research.

Boat: 97 SeaRay 4.3L 175

Problem: Last two years its been hard to cold start after sitting for 1+ days. This years has progressed to be even harder to start. The only way I can seem to get it to start is by using starting fluid or pouring gas down the carb. Once it starts and finally achieves idle, the boat will run like a champ all day. But, starting it can be a 15-20 min process.

Research:
1. Check the oil pressure switch - if the oil pressure switch was faulty, wouldn't it not allow the engine to run at all? (bc the fuel pump is not being fed the voltage to run). The boat runs fine, once manually feeding the engine with gas.

2. Changed out the fuel filter - still no solution. The fuel filter did hold gas, so I know the fuel is not sneeking back into the fuel tank.

3. On the double barrell carb - Sometimes fuel squirks out and sometimes not (when priming from the throttle). The carb was replaced 3 years ago by a dealer. But idles and runs fine once the engine is going. I beleive the carb should be fine.

I am very fimilar working with engines. I've built a few competition skis and keep my other powered toys running correctly. But can not figure this problem out. So, any sugggestions or tips would be greatly appreciated.

 

[Doernuth]

Re: Mercruiser 4.3 Engine hard to cold start!

Is the choke working properly? Also check for vacuume(sp?) leaks.

Are the plugs fouled? When was the last tune up?

 

[bign1514]

Re: Mercruiser 4.3 Engine hard to cold start!

Choke - Last time i checked it was working but will check again this weekend to be forsure.

Tune-up - had a tune up in 2007 and put about 35+ hours since tune-up.

Haven't checked for vaccum leaks bc everything seems fine once the engine is running.

Boat is an hour away at our lake house. Trying to gather as much as info before I go down and fix the problem this week.

 

[Don S]

Re: Mercruiser 4.3 Engine hard to cold start!

Problem: Last two years its been hard to cold start after sitting for 1+ days. This years has progressed to be even harder to start. The only way I can seem to get it to start is by using starting fluid or pouring gas down the carb.

Do you use throttle only position of the throttle? Do you pump the throttle lever a time or two to prime the engine? Do you give it some throttle when cold starting?
It's not EFI like your truck.

 

[Doernuth]

Re: Mercruiser 4.3 Engine hard to cold start!

Based on your answers I would change the plugs, wires, cap and rotor.

Also check the choke. Maybe consider a carb rebuild.

 

[bign1514]

Re: Mercruiser 4.3 Engine hard to cold start!

I always prime it (3-4 times) with the throttle. Then put the throttle in 1/4 positions (in netrual) and try to start it. -- this is what a local mercruiser mechinic has told me.

 

[bign1514]

Re: Mercruiser 4.3 Engine hard to cold start!

what are the best plugs for these engines?

 

[Doernuth]

Re: Mercruiser 4.3 Engine hard to cold start!

The ones recommended in the manual. The recomend them for a reason.

Any quality plug AC Delco, Champion, NGK, Autolight will work just make sure that they are gapped correctly.

You can get them from your local merc dealer.

 

[egldvrbags]

Re: Mercruiser 4.3 Engine hard to cold start!

Hello all, I've been reading here for awhile and always find the answers to my problems (thanks for providing the support). But, I can't seem to find the answer to my one big problem after doing lots of research.

Boat: 97 SeaRay 4.3L 175

Problem: Last two years its been hard to cold start after sitting for 1+ days. This years has progressed to be even harder to start. The only way I can seem to get it to start is by using starting fluid or pouring gas down the carb. Once it starts and finally achieves idle, the boat will run like a champ all day. But, starting it can be a 15-20 min process.

Research:
1. Check the oil pressure switch - if the oil pressure switch was faulty, wouldn't it not allow the engine to run at all? (bc the fuel pump is not being fed the voltage to run). The boat runs fine, once manually feeding the engine with gas.

2. Changed out the fuel filter - still no solution. The fuel filter did hold gas, so I know the fuel is not sneeking back into the fuel tank.

3. On the double barrell carb - Sometimes fuel squirks out and sometimes not (when priming from the throttle). The carb was replaced 3 years ago by a dealer. But idles and runs fine once the engine is going. I beleive the carb should be fine.

I am very fimilar working with engines. I've built a few competition skis and keep my other powered toys running correctly. But can not figure this problem out. So, any sugggestions or tips would be greatly appreciated.

I have a '95 4.3LX w/ a 4bbl carb, electric fuel pump. I had a similar issue until I figured out a good starting sequence. What happens on mine is that after several days, the fuel evaporates from the bowl in the carb. Here's what I do and it works like a champ.

1. The electric fuel pump operates during the starting cycle when you're actually cranking the engine. I pump the throttle twice and then open it a 1/4th. Then I crank for about 20 seconds. This allows the fuel pump to run and fill the bowl. If there is fuel in the bowl already (ie, it hasn't been long enough for it to evaporate), it will start during this period.

2. If it didn't start during #1, I turn the key to off and pump the throttle twice more and then open it to 1/4th. Then she will fire right up.

Here's a thread from about 3 yrs ago discussing this....

http://forums.iboats.com/showthread.php?t=278075

Hope this helps.....

Bags

 

[Bt Doctur]

Re: Mercruiser 4.3 Engine hard to cold start!

I wire a momentary on- off- on switch thats allows me to prime the engine after carb or filter work.
in case the pressure switch goes bad, you can always use the "on" as an emergency to get back instead of shorting it out.

 

[dearoledad]

Re: Mercruiser 4.3 Engine hard to cold start!

So, bign1514, did you get a resolution that worked? I have a 1987 SeaRay 175hp that does exactly the same thing. I also need a solution. I have tried every throttle sequencing idea imaginable. I read the thread at the link egldvrbags provided but jumping electric points or installing a switch to run the pump seems to me to be getting around the problem rather than fixing it. After all, my boat ran 23 years before this started to happen so clearly something has worn out; the question is it that what has worn out?

 

[Bondo]

Re: Mercruiser 4.3 Engine hard to cold start!

After all, my boat ran 23 years before this started to happen so clearly something has worn out; the question is it that what has worn out?

Ayuh,... Welcome Aboard,...

It's usually the gas leakin' through the carb, 'n the time for the fuelpump to refill it, to start...

 

[bign1514]

Re: Mercruiser 4.3 Engine hard to cold start!

Dearoledad -

I never did find out what was wrong. Last time I had the boat out was in beginning of august. Then my schedule got full and didn't allow me to work on it more. The weird thing is... I winterized the boat this past week and it only took me 2 trys to get the boat started. I was shocked. Because it sat for 3 months without being run. So if anyone have any idea please shoot them my way.

I checked the fuel pump and It was working properly. Gas was filling up the gas fuel filter. I believe there maybe something block gas from being squirted into the car.