Dutch Guy asks 200HP throttle problem

[satleecher]

I bought it, asked a pensioned person to prepare the motor working, had at least 3 years of non running hours (costed me about 500 US$, but still worth it, I think). I boated for about 15 hours, last week everything ok, but I noticed that the stationary was higher then usual (choke closed). Today with my family... starting conditions as usual...that is..open choke. pull twice..he will then say 'whroaaahhhh.....' and stops (normal), close choke, pull twice and working. Also today, and again I noticed higher stationary...pulled on mercontrol in shift and off on stationary to exit the habour....normally then push throttle further for the sound and power....then.... blup-blup... motor stopped. Shift in N, pull and start without problem, in shift again, still ok, throttle further...end again. This I tried several times no succes. We boated back on stationary and ended the trip.... I have a theory that maybe the motor after three years is now 'cleaned' and that air/fuel is the problem. So too much fuel or too less air when opening the throttle. But I have NO CLUE where to adjust. Or could the timing be shifted? Who can help me. I am afraid to go the pensione person... he like to charge.... I expect it's a small item. Thanks for any help. Dag en bedankt (like we say in dutch).

 

[satleecher]

Re: Dutch Guy asks 200HP throttle problem

During the preps for starting I did pump more gasoline to engine, could the carter be filled with fuel and supply then the carb. with too much gasoline when pulling the throttle further? I read this on scooter-forum 2-stroke engine. If so, how long before this carter is emptied by gasoline?

 

[j_martin]

Re: Dutch Guy asks 200HP throttle problem

You need to understand the basic operation of the engine. It would help if you looked around the site and picked up on the words used. I will attempt to interpret here:
stationary = idle
carter = fuel pump (carter is a brand)

Some confusion on choke position. Open is the running position. Closed is the starting when cold position.

Unless one of the very early ones, this engine likely doesn't actually use a choke, but a fuel enricher valve of some kind.

Now I will attempt to help, but first I need to know more about the engine.
1. Carburetors or fuel injection
2. Approximate year of manufacture
3. Serial number.

hope it helps
John

 

[les morgan]

Re: Dutch Guy asks 200HP throttle problem

I am no expert but I had a similar problem with a merc 90hp. Idled just fine
whether in gear or in neutral but died when accelerated. Found a pin hole
in the squeeze bubble. Maybe you will be lucky like me. Easy fix.

Les

 

[satleecher]

Re: Dutch Guy asks 200HP throttle problem

Thanks John,

Yes, I understand the terminology vai your help. It's HP200 Mercury Thunderbold; year 1975?-1984?. Has an mechanical carb with optional/removed electric starter. No serial number present, has been sorted out with insureance company. I hope you may and can help me. My wife and kids to not trust the engine too much anymore, but I believe it's also lack of experience by myself. The interpretation you made is correct. What I suspect is that by handpumping the gasoline for a first start, I pump too much so that start/idle works but when I throttle somewhere gasoline is trapped and release in carb and then kills it. It also kills when using the lever for cold-engine (stationary control). My poor understanding could need some guidance.

 

[satleecher]

Re: Dutch Guy asks 200HP throttle problem

I am no expert but I had a similar problem with a merc 90hp. Idled just fine
whether in gear or in neutral but died when accelerated. Found a pin hole
in the squeeze bubble. Maybe you will be lucky like me. Easy fix.

Les

It's a brand new squeeze bubble, but I will of course check it. I do not think air leakage is the issue here.

 

[CharlieB]

Re: Dutch Guy asks 200HP throttle problem

Dutch Guy

I suspect that the carburetors are slightly too lean in the idle mixture.

Does your model have the choke butterfly valve in the front of the carb throats?

If so, then pull the choke lever just a little bit to close those plates about 1/4 of the way, put the motor in gear and start opening the throttle. Does that improve the motor speed and power?

If so, then we need to identify those carbs and the idle mixture adjustment screws, turn those screws (6 of them) Counter-Clockwise just 1/8 turn.

Test the motor again.

If this does NOT improve then it may be time to clean all carburetors again.

 

[satleecher]

Re: Dutch Guy asks 200HP throttle problem

Charlie, I will try it. Yes, butterfly choke in front is the case. 6 screws on carb, oh boy... it will try to find them, it if the 1/4 trick makes a difference..

 

[j_martin]

Re: Dutch Guy asks 200HP throttle problem

I don't know that I've ever heard of a 200 hp thunderbolt, but then again there's lots of thing I haven't heard of.

Is this a V6 engine, or inline 6?

Your theory about pooled fuel is invalid. There's no place to store it.

You either have weak spark, or more likely, are running lean at idle.

Also there could be a problem with the throttle (and timing) linkage.

Running lean could be caused by plugged main jets. It would lean out slightly at idle and the motor would race (run faster). On throttle advance it would die immediately for lack of fuel.

Plugged main jets could be caused by rubber parts, hoses, etc failing and putting debris into the carburetors. Older engines are known for this until the hoses are changed.

If you take some pictures of the engine with the covers off and post them, we might be able to figure out about which engine it is and recommend a maintainance manual for it. Maybe even in Dutch.

hope it helps
John