78 chrysler 85 - won't idle long - misses under load low rpm's

[1badchrysler85]

I just purchased my first boat from my brother that he owned for about 2 years. It is a 1977 sportsman 15' runabout with a 1978 85 horse Chrysler outboard. Here is a list of problems I am having with it: <br />It will not start when it is cold without a shot of pre-mix directly in the carbs. After it starts the first time it will start without the starting fluid.(No big deal) After idling for about a 30 seconds it dies. If you let it sit for about a minute it starts right back up but dies again after about 30 more seconds.(this is in the water or on the muffs) The primer bulb pumps up and stays hard. The fuel tank is also vented. After getting it started, if you can manage to get it in gear before it dies, it misses under a load. If you really give it throttle the boat jumps out of the water and runs great. I could run it all day long. It doesn't miss at higher speeds and has plenty of power. As soon as I bring the throttle back down it starts running rough again and as soon as I bring the throttle to idle it dies. After sitting a minute or so it starts right back up and does the exact same thing. The boat also did this when my brother owned it but he is the type of person who won't fix it unless it is completely broken. These are the things I have checked or replaced:<br />I put a new battery, starter and plugs in it. It has fresh gas mixed 50:1. I replaced the fuel pump diaphram. The fuel screen is clean. The gas can is clean. I pulled the bowls off the carbs - no sign of laquer or dirt. Choke/throttle flaps working fine. It has spark on all three cylinders. Any advice would be greatly appreciated.

 

[eurolarva]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

Hello badchrysler and welcome to Iboats. When you start the motor do you choke it. This is done by pushing the key in. I did not read it in your post and a lot of people myself included did not know about this choke. When motor tries to die does it help to choke it. My guess is in spite of the clean looking carb that it needs to be taken apart and cleaned and a rebuild kit needs to be put in it. YOuc can get one from NAPA for around 15 dollars and their part number is 18-7037. When cleaning it use spray carb cleaner or just fresh gasoline and use a piece of wire to go though the jets and small orifices in the carb. You may want to pop the welsh plug out and clean those holes out as well. Replace any old fuel line and use good quality fuel clamps on all the hoses. Also when you pull the idle mixture adjust screw out to replace the spring that comes with the rebuild kit check the tip of the screw. It should have no pitting on it and the tip should be almost pointed. If it is scratched or pitted try using some emery cloth to buff it out<br />Good luck and if this dont fix it please post back

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

eurolarva, thanks for the reply. The choke also works fine but doesn't help. I will get some rebuild kits and give it a shot. I am also going to decarbon the cylinders. Do you know anything about the reed valves? Thought I would take a look at those when I have the carbs off. <br /><br />Thanks,<br /><br />Cory

 

[eurolarva]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

I dont know much about the reed valves. Mainly that if they are chipped or broken they need to be replaced. My manual says when you take the carb off you should blast them with WD40. I am not sure what good this does but I do it when I worked on my carb. You say choking it dont help to keep it running? When you do the carbs do only one at a time. Do not mix parts from the different carbs and replace them in the order you took them off the motor. Do you have a manual? Your problem may be adjustments. The manual has a section for link and sync.

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

eurolarva,<br />I pulled the carbs apart yesterday and made sure they were clean. The middle carb was full of junk. All the jets and gaskets look to be fairly new. I looked at the reeds and they seem to be in good shape. I gave them all a good shot of wd-40 like you said. I then replaced all the fuel lines, fuel tank & connections and the primer bulb. I also put in a new ignition switch, temp & volt gauge and an inline fuel filter. The boat started right up without using the choke or shooting pre-mix into the carbs. My wife and I loaded our stuff up and went to the lake. The boat ran great. I put some sea-foam decarbing solution in the gas and ran a tank through it. The only problem now is that it still doesn't want to idle for very long (about 10 seconds). If I put it in gear and give it some throttle it runs fine. As soon as I pull the throttle back to idle it dies but starts right back up (for about 10 seconds) as soon as I hit the ignition. Do you know what temperature I should be running at? I can't find it in my manual. <br />Thanks for the info.

 

[eurolarva]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

Can you post your model number? There are different models for that year. My guess is it is a 110 degree thermostat F528068(merc number). Also what kind of spark plugs do you have in there? Did you replace them after doing the decarb? What octane gas are you using. <br /><br />Your idle problems may just be the mixture adjustment on the carbs. Did you adjust these after you rebuilt the carbs?

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

eurolarva,<br />the model number is 857HE. I just found out that it is actually a 1973 . I bought an impeller pump kit last night and the place I bought it had a listing of the model numbers and years. I also want to replace the thermostat. Can a get one through an auto parts store? Do you know the thermostat part number and temp range for this motor? I did replace the plugs. I think they are NGK BU7HW. I'm trying to remember off the top of my head. It had NGK B7HS plugs in it. What plugs do you think I should run? The B7HS plugs are a cross reference and a buck cheaper. I am running 87 octone gas. I have heard not to run premium in older outboards. I set the idle mixture screws at 2 1/2 turns out(1 1/4 full turns). I haven't tried adjusting them with the boat running. After I replace the impeller and the thermostat I plan on going through my manual and checking all the linkage adjustments. I have the chiltons manual and would not recommend it to anyone. So far it has been pretty useless. Wish I would have found this site before I bought one. <br />Thanks Again,<br />Cory

 

[eurolarva]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

The links I use for outboard parts do not go that far back. Newest model for an 85 chrysler is like 1979. My clymor says All Magnapower ll models use UL18V and all other 3 cylinders use L20V plugs. I also cant find any information on the thermostat. If no one helps you on these issues you can try http://www.chryslercrew.com/. They have a chat on thursday nights and they will be able to tell you what parts you need.

 

[scotiany]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

I know I sound like a broken record but, did you check the puddle valve screens and reeds for cleanliness? If they're plugged up, it will cause problems at idle and low speed but not necessarily at cruising speed.

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

I found the OE part# for the thermostat (I can't remember which link) and was able to order it through NAPA. I dropped the lower unit and replaced the impeller pump and housing yesterday. That was a piece of cake! I believe the L20V is the champion plug for my motor. I will definitely check the puddle valve screens. We plan on taking the boat out sunday so I will let you all know how it runs.<br /><br />Thanks,<br /><br />Cory

 

[scotiany]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

Here's what I got out of Seloc manual. Plug-L20V, Ign. timing at WOT-32 Deg BTDC. Idle RPM 700-750. Should have a Magnapower IV system. You may have to cross reference the plug. NGK should also have a suitable sub.

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

I cleaned the puddle valve screens today. They were full of crud. My new thermostat also came in today and when I went to install it I found out that it didn't have one in it to begin with. The new thermostat seemed a little small so I looked in my manual and it shows it having a grommet. Does anyone know where I could find one? I installed the thermostat anyway. I figured it would be better to have it loose than not in at all. We are going to take the boat on a test run friday. I will post again after we return.

 

[eurolarva]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

The mercury part number for that grommet is 25-F84504. It cost about 5 dollars. The gasket is 25-F84504.

 

[1badchrysler85]

Re: 78 chrysler 85 - won't idle long - misses under load low rpm's

The boat ran great this weekend. Still need to work on the idle though. I just got a 55 gallon drum to run the motor in at home. I might need to slightly modify it due to the size of my motor. With the thermostat installed the boat ran warmer than the first 2 times I had it out. The new impeller is pumping 2 to 3 times as much as before. I need to find a new temp. sending unit because I think the one in the motor doesn't match my gauge. I have a teleflex sportsman gauge. Without the thermostat in the gauge reads a constant 180. With the thermostat in the gauge reads a constant 200. I know the boat isn't actually running this hot or it would have siezed by now. Teleflex sells a 3/8" or a 1/2" sending unit. The sending unit in the boat is very small. Anyone know if the 3/8" S.U. is the right one?