1983 Merc 150

" I am having problems with my

" I am having problems with my motor being hard to start wwhen it is cold out. Once started, I have no more problems the rest of the day. All of the normal things have been checked/replaced. The motor did sit for several years before I got it about 2 years ago. Is it possible some of the gaskets deteriorated and are leaking when cold? "

"Bill,

Make sure the choke

"Bill,

Make sure the choke is fully operational. The shutters should close completely when the choke is applied. I have a feeling you have already done this as well as removed and cleaned the carbs.

Older engines can be tough to start when cold. This can be due to low compression or low vacuum.

You can't do very much about low compression other than rebuilding the engine.

Low vacuum can be a result of worn rings also, but it can be caused by quite a few other things as well. Reed valves that are not closing properly can cause this. Leaks in the bleed hoses can also contribute. That engine may have one-way check valves in the bleed hose fittings which should be checked. Worn or cracked crankshaft seals might be a factor.

I have worked on engines with starting problems like this, and a few times I never found anything that I could identify as a problem. Rather that take the whole engine apart, and still not find anything wrong, on a few I noticed that if a little fuel was sprayed into the carb bores the engine would start fine. On these I tried a somewhat unorthodox approach. I installed a pump or valve type of choke which they used on later models. These chokes allow a small jet or stream of fuel into the bore, carb flange, or intake manifold, either directly from the pressure line out of the fuel pump,or from the upper carb's float bowl. This worked very well. Some of these engines have been running like this for over five years, and I have not had any complaints from the owners.

"

Thanks for the reply Tony. Th

Thanks for the reply Tony. The engine uses the enrichner type choke rather than the old conventional butterfly type. Compression is 118-120 on all 6 cyls even tho 1 & 3 are slightly scored. I replaced the top seal but I'm beginning to think I need to replace the bottom along with all the gaskets. If I go that far I might as well do a complete overhall.

" Bill,

The enrichener chok

" Bill,

The enrichener chokes were not used until much later, so someone must have adapted the choke, or the engine is newer than you are aware of.

Ususlly these chokes draw fuel from the float bowl of the top carb, so it works on gravity. I have changed that on many engines. I simply rerouted the hose so that the choke draws from the pressure line from the fuel pump. Of course you have to plug the fitting on the top carb also. Then when the choke is engaged, you get a jet of fuel shooting into the carb instead of a little trickle. Also, if the choke draws from the top carb, only the two bottom carbs actually are choked. Since the system uses gravity, the top carb cannot supply fuel to choke itself. In that case the top cylinders get no extra fuel when choking. This can be corrected by using the pressure line to supply fuel to the choke valve.

The scoring on the cylinder walls is not a good sign. Even though you have good compresion, the scoring indicates that those pistons probably need rings. It can only get worse. If you plan to keep the engine, I would advise you to rebuild now, before it gets any worse.

Good luck, whatever you decide to do.

Tony "