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1979 175hp Merc problem

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Armin

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" I have a 1979 175hp Mercury

" I have a 1979 175hp Mercury outboard that displays the following problem:

When I first try to start it it just turns over but will not start. If I crank it long enough it will eventually catch, fire a few times and die.

If I repeat this often enough it will eventually fire and continue to run but as soon as I try to give it any throttle it dies.

If I do not give it any thottle and just let it idle for about 5 minutes or more, it will eventually let me give it throttle without dying but there is still a noticeable hesitation when I first give it throttle. Once it gets past the hesitation and get up to planing speed it run fine... lots of power and no hesitation as I give and take away throttle while driving.

If I then stop and turn of the engine and restarts it within a few minutes it start fine and only has minimal hesitation when I apply the throttle. However, if I let it sit for 30 minutes I have to start to "warm-up" process all over again.

It's almost like it can't get past the low RPM range but once it does it runs just fine.

I have replace the fuel pump and spark plugs and had the carburator cleaned but it made no difference. "
 
Check the Thermostats. It so

Check the Thermostats. It sounds like the motor is not getting enough fuel.
 
" Sorry, Hit the wrong button.

" Sorry, Hit the wrong button. It sounds like the engine is running very lean until it warms up. Check the thermostats to make sure they are working. Also, check your choke valves on this engine. Problems have been associated by the butterflys not working correctly.
Good luck "
 
" I checked the choke valves a

" I checked the choke valves and the butterflys appear to function correctly when I push and release the choke buttton on the controls (i.e.- they open and close).

How many thermostats are there?

BTW, Thanks for your advise. "
 
" There should be a thermostat

" There should be a thermostat on each head at the top of the engine. Pull the thermostat cover and check the stats. Also, how long has it been doing this? "
 
" The engine never missed a be

" The engine never missed a beat since I bought it in 1979, then last year it started to hesitate a little when pulling skiers out of the water. By the end of last summer it had progressed to significant hesitation and occasionally dying when applying throttle to pull up a skier. This year it deteriorated to the point where the engine is very hard to start and towing skiers is all but impossible.

I took it in to a mechanic and he cleaned out the built-in fuel tank, replaced the external water seperation/fuel filter, checked/cleaned the internal fuel filter, put a new diaphragm in the fuel pump, pulled the carbs and cleaned them, and replaced the plugs. So far none of this has helped.

He then checked the compression and found 4 cylinders at 110 lbs. and 2 cylinders at 100 lbs. so he pulled the head because he felt the head gasket might be damaged and a bit of water might be leaking into the 2 lower pressure cylinders. Turns out the head gasket did not have any obvious damage. Right now we're waiting for the new head gasket to arrive so he can put it back together and see if it makes a difference.

He also said something about an electrical component (can't remember what he called it) that is located under the flyhweel that looked a little fried/melted. He said only the plastic cover over it looked melted and he thought that the componenent itself should be OK.

I'll ask him to check the thermostats to see what he finds. If you can think of anything else to check please let me know. Thanks for your help. "
 
" Armin... Been reading your c

" Armin... Been reading your comments and honestly don,t know what the problem may be. I have been a merc tech for 15 years and suggest you might consider finding a new mechanic. If he,s done everything you said and done compression checks after trying everything else that bothers me. Seems like he,s fishing for a solution. Just my personal opinion,hope your not offended...DJ "
 
" Thanks DJ. No offense taken.

" Thanks DJ. No offense taken. I'm starting to wonder about his problem solving skills myself, that's why I posted my questions here. Seems like I'm spending a lot of money on parts and labour that haven't helped fix the problem.

I may have to take your advise and find a new mechanic if the new head gasket doesn't do the job.

Thanks for the input. "
 
" Armin... I wouldn,t hold my

" Armin... I wouldn,t hold my breath on the gasket working. Its funny, I,ve been thinking about your problem all day. The only thing that comes to mind from your explaination of the progressing problem is a plugged or restricted exhaust which I admit would be rare. There was a service bullitin issued by Mercury a few years back for drilling a whole in the midhousing for exhaust relief but I DO NOT know whether you motor qualifies. I,ll keep on thinking on a solution and if I come up with anything I will let you know...DJ "
 
Thanks DJ. I'll post an u

Thanks DJ. I'll post an update when/if I get it fixed.
 
DJ: Got my boat back yesterda

DJ: Got my boat back yesterday and it now runs great. According to the mechanic the problem turned out to be the trigger. Apperantly something had gotten on to the trigger and frozen it in the fully advanced position. He freed it up and now it starts and runs great.

Does this make any sense?
 
" ARMIN...NO, The trigger adva

" ARMIN...NO, The trigger advances with the trottle so from what you have written I wouldn,t think that was the problem. I do not see how the motor would even advance timing or throttle with the trigger in a fixed position. The trigger is attached to the trottle arm at the top under the flywheel so if the trigger was stuck you shouldn,t be able to advance your trottle at all...DJ "
 
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