Engine dies shifting into gear when hot.

[Waterboy65]

The engine is a 1981 (385 hours) 228 Mercruiser (305 CID Chevy) in a 20ft Slickcraft kept on a trailer. It has started to die when shifting into gear from neutral (both forward and reverse) only when hot (after being run for 20 minutes or more). It works perfectly when engine is cold or after it's been shut down for 25 minutes - the only way to get it in gear to get home. I've tried the following: Replaced wiring and coil, rebuilt the carb, replaced the stern drive unit shift cable, replaced all parts normally associated with a tune-up and performed total tune-up. I've also tried bypassing the cut out switch and going completely through the setup procedure again to no avail.

I've got the risers and manifolds off for cleaning and am willing to repeat any procedures or try out any ideas to get the problem resolved; I'm simply clueless at this point.

Looking forward to input - thanks in advance.

 

[boltonranger]

Re: Engine dies shifting into gear when hot.

Well; I'm by no means one of the Ancient Mariners-
so if there's something about the cutout switch that fails more easily when hot, I wouldn't know that.
but - either the fuel delivery is changing or; the spark delivery is changing (when it's hot.)

Since you said you replaced the coil - perhaps fuel is the issue.

You never mentioned your choke etc. Consider this:
Perhaps the carb isn't set quite right.
When it's cold - the motor runs because the choke compensates.

When it's hot - it's too lean; and as you close the throttle to shift - the mixture is far enough off that it quits.

You could close the choke manually when it's hot and see if wants to run - if so just enrichen the mixture of the carb.

-br

 

[searay3]

Re: Engine dies shifting into gear when hot.

Are you using a manual to make the adjustments. There is a procedure. I have an 86 alpha and am not sure if yours would be the same. There are posts that may give you a link to the proper manual. It states in the adjustment procedure final adjustmensts are made on the water. I had an opportuninty to get on a deserted lake on a calm day and was able to make the final adjustments without interfering with anyone. You cannot make the final adjustments without a load on the prop.

 

[Waterboy65]

Re: Engine dies shifting into gear when hot.

Thanks for the ideas.

Although I also can't figure out why the cutout switch would be sensitive to operating temperature, I will check both spark and fuel delivery while hot and try the choke experiment.

I was using my Seloc Mercruiser Manual to make the adjustments but was doing them while running off a hose in the driveway. I did adjust the idle while in the water.

I was able to get another cut-out switch set up procedure off this web site so I'll compare it to the manual and go through the procedure again.

It will take a few days to get this done but I'll get back with the results.

I'll post the final solution for the benefit of others.

 

[Mjust]

Re: Engine dies shifting into gear when hot.

Meter your ignition coil against specs, both primary and secondary sides. Does your coil have an internal resistor or an external resistor?

 

[brodie6]

Re: Engine dies shifting into gear when hot.

The engine is a 1981 (385 hours) 228 Mercruiser (305 CID Chevy) in a 20ft Slickcraft kept on a trailer. It has started to die when shifting into gear from neutral (both forward and reverse) only when hot (after being run for 20 minutes or more). It works perfectly when engine is cold or after it's been shut down for 25 minutes - the only way to get it in gear to get home. I've tried the following: Replaced wiring and coil, rebuilt the carb, replaced the stern drive unit shift cable, replaced all parts normally associated with a tune-up and performed total tune-up. I've also tried bypassing the cut out switch and going completely through the setup procedure again to no avail.

I've got the risers and manifolds off for cleaning and am willing to repeat any procedures or try out any ideas to get the problem resolved; I'm simply clueless at this point.

Looking forward to input - thanks in advance.

I had the EXACT same problem, it drove me nuts. Turns out we (me and my neighbor) screwed up the re-build of the carb.
After sending it out to my local mechanic and having it re-re built it worked flawlessly. I forget what we did wrong (maybe the float was set wrong?) but what ever it was he fixed it and it runs great.
BTW some of the guys here hate the Seloc manual which is what I used to help rebuild the carb. They like the OEM manual.

 

[wcsparky05]

Re: Engine dies shifting into gear when hot.

sounds to me that maybe your boat is not cooling properly. have you drained the raw water ever? mine had sand and mud in it so when i opened the valve nothing came out. i had to poke a coat hanger up in it to get the gunk out. replace your thermostat too. they cost $5 and are easy to peplace and can save you a lot of dough if you overheat and dont know it. good luck.