Chrysler 70 hp... why does engine surge?

[mklearl]

I have a 1979 Chrysler 700 skier engine 709h9a and am not by any stretch of the imagination an outboard mechanic. I have been learning as I go. Anyway, I have fixed several issues. This one has me stumped. I have taken the carbs off and cleaned and put new kits in them. The number one carb had fuel coming out of the vent hole. Ive taken the carb off numerous times and tweeked and put new gaskets. I finally have it down to barely a drip... leads me to believe that the needle isn't seating properly.... but it's a brand new needle. So what gives? I was extremely careful to measure the distance from the float bottom to the top of the bowl gasket... 13/32" as recommended.

Also, when trying to sync the carbs, the engine will surge... rpms go up and then go down, up and down. Is it possible that it is just the float that is bad? This could cause the engine to surge and the needle not to set, no? I know that I can take the carb off AGAIN and put the float in some fuel and see if it floats... But I'm trying to avoid having to take the carb off again without any input.

One last thing... when syncing, if I turn the idle mixture screws in, they dont bog the engine down at all.. I start off open about 7/8 of a turn as recommended. The engine sputters. As I turn the needles clockwise, rpm's increase... but I can go all the way to lightly seated and the engine never skips a beat. I replaced all 3 needles, and there is no change.

Thanks in advance for any input.

 

[jerryjerry05]

Re: Chrysler 70 hp... why does engine surge?

Start with a compression test.
then check the diaphram.
The reeds ok?

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

reeds?

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

I will be checking the compression later. I also have been reading up on reeds. Sounds like this could potentially be the problem... backfired twice when starting, over rich even though idle needles are closed. Also, I don't have to pump the primer bulb to start even if it has been sitting for a day or two. Any other symptoms or thoughts? I'm really trying not to get that deep into the engine.

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

I'm beginning to think the problem is bigger than I can handle.... I'll throw it out there anyway. First of all, compression was 60 on all three cylinders. When I was cranking the engine, it popped and turned over. sounded like it always does. Why would it start with only 2 plugs and the compression tester in there? Sorry for the stupid questions. I won't learn if I dont ask! I really don't have anything to lose. Thanks for any input!

 

[procraftguy]

Re: Chrysler 70 hp... why does engine surge?

Float/float needle problem you are filling up without stopping. Have u noticed leaking fuel ? This would cause needle adjustment to seated to still run (fuel over flow through throat )i if u tryed to throtal up at full seat it would die .know starting with 2plugsu in yes could with just one think basics lawnmower 1cylinder it runs. Next time pull kill switch to check compression turns over no spark hope that all help happy boating

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

Yep, I figured out my stupidity while doing the compression test again. I was origionally thinking the float... That carb has been rebuilt, has new needle, and like I say, I have the leak down to a small drip! Still leaking though. I will probably tear the carb apart again and try a new float. If i flip the carb upside down and gently blow in it no air goes through and vice versa right side up... so the needle is setting properly. It may not be floating up though. If that doesn't work, I'll try the reeds... keep it simple first. Anyone have any thoughts on why it may or may not be the floats and why it may or may not be a bad reed? Also, I don't think the engine has ever been de-carbed, so I'm going to do that once I get it up and going again. That should help with the compression... I hope!

 

[procraftguy]

Re: Chrysler 70 hp... why does engine surge?

Reeds. why not. your running with adjusted all the way in that means fuel is still getting in intake or it would die in no more then 10 sec per service manual (time to burn access fuel) only way is it has to go through float bowl to get there either through your needle adjustment or fuel over flow .unless u overtightened adjustment needle and groved it.

 

[procraftguy]

Re: Chrysler 70 hp... why does engine surge?

Compression 60 across ? spray some two cycle in cylinders and try again .if there all at 60 thats tbe tester if it was a major compression problam the readings are never right at same place there ussally 15-20 lb span in 1 or more cylinder and id use merc tuner its givn me good results

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

Makes sense to me. I put new idle needles in last night. Thanks for the input... I was getting discouraged!

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

Pep Boys loaner tester... I wasn't overly impressed with it and had a feeling it wasn't working properly or I was doing something wrong. Still will decarb. Not sure if it has ever been done and if it has been running overly rich it will definately need to be done now. Thanks again.

 

[procraftguy]

Re: Chrysler 70 hp... why does engine surge?

Np iv been there and after many troubles myself iv learned alot not as much as some but found most hard problem s are the easiest fix... if u can find it hope it works out let us know to help other serchers with same?

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

Definately will. I probably cant get the float until monday at the earliest, but may take the old one off today and put it in some fuel to see if it floats. Thanks again. I hope you're right!

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

So I took the float off the leaking #1 carb and put it in a bowl of fuel and it floats. New needle. What now?

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

Update. Removed all three carbs for a rebuild... did that and everything seems fine. Still couldn't get the engine to die by closing all of the idle mixture needles. I backed off the idle speed screw a little until it died. Fired it back up and backed out the needles a bit and started to get some response by closing the needles... I think this is possibly a result of someone (ie. me) tinkering with idle adjustments without not knowing what they were doing! Getting it in the water today and going to try to sync the carbs and THEN set the idle speed screw. It's near impossible to do on muffs. Hopefully my theory is correct.

 

[mklearl]

Re: Chrysler 70 hp... why does engine surge?

So I'm stuck on a tugboat for two weeks and it gives me a great opportunity to go over the seloc manual.... learned tons in just a couple of days. Anyway, I was reading up and think that the reason I can turn the mixture screws in all the way and not have the engine die is because the cylinder drain system isn't working properly. Engine is too rich, idles rough, and has died on me, especially when running at low rpms... sounds like a place to start. With that being said, do I just have to check the hoses for clogs, do I need to remove the cylinder drain cover, and the valves that the manual is talking about... are these just one way valves... they seem just like elbows to me. Also, would it be worth it to change the reeds on the cylinder drain plate while I have the cover off? I'd like to order the parts needed so they are there when I get home and I can actually work on the boat for a day or two and then enjoy it for a couple of weeks! Thanks for the input!

 

[jerryjerry05]

Re: Chrysler 70 hp... why does engine surge?

Set the carbs at 1 turn out and leave there until your ready to final tune in the water.
The rpm's in the drive.About 1200.
Top post in the Force/Chrysler forum is a thread called a linc and sinc. Do this.
Check for spark?
Comp at 60 is probably the gauge.
The results are all close within 5# of each other,that's good.
Get a different gauge and try again.
Set carbs at 1 tun out.
Rebuild the fuel pump.
Check the reeds?