Mercury 9.8 stalls in reverse

[danw77]

First post, here goes...

This is a new to me boat and outboard, so I'm not sure of the history. It's a 1966 14' Starcraft with a 1975 (I think) Merc 9.8. When in reverse, the engine cuts out as soon as I begin to apply the throttle (no problem in forward). Sometimes I can keep it running by feathering it just right, but most of the time it dies. This also only seems to be a problem when out on the water. It runs/shifts fine in a 50 gal drum. Another thing I noticed that seemed strange is that it won't start with the choke on - only with the choke off. It also seems to have a rough idle. Not sure if those are related to the problem or not. All in all, it runs well enough that I can use it and get where I'm going, but I'd certainly like to get these issues figured out.

Thanks in advance. I am a total newbie, so any help would be greatly appreciated.

 

[ben2go]

It sounds to me like the carb(s) need to be cleaned and possibly rebuilt.Could possibly be points and condenser or plugs.I would or have done a full tune up and carb cleaning.

 

[sparkbr]

I would start with cleaning the carb. you most likely have the air side of the idle circuit restricted/plugged

 

[danw77]

Thanks for the fast responses. I have a manual on order, so I will make sure to clean the carb. FWIW, the guy I bought the motor from fixes them up and then resells them. He said he cleaned the carb, but maybe he didn't or didn't do it well enough.

 

[ben2go]

You could have still gotten junk in the carb from the tank.The passages in side the carb are almost as small as a hair so it doesn't take much to plug them.

 

[danw77]

It has a new tank and line, but I'll clean it anyway. Which should I order, the carb rebuild kit or just the gasket kit?

 

[ben2go]

For cleaning,a carb gasket kit,but it's always good to have a rebuild kit on hand while cleaning.Never can tell when you may find something bad or broken.I should have asked.Have you been using the low grade gas with ethanol blended in?Ethanol has a bit of water mixed in and can sometimes fowl things up.Not to mention that ethanol breaks down gaskets,rubber, and plastic parts.

 

[Captain Ahab]

The stalling in reverse sounds like your linkage is out of adjustment or binding. Watch closely how the throttle linkage works in forward - it should do exactly the same in reverse

 

[danw77]

For cleaning,a carb gasket kit,but it's always good to have a rebuild kit on hand while cleaning.Never can tell when you may find something bad or broken.I should have asked.Have you been using the low grade gas with ethanol blended in?Ethanol has a bit of water mixed in and can sometimes fowl things up.Not to mention that ethanol breaks down gaskets,rubber, and plastic parts.

Yes, the only gas I can get here in NJ has a 10% blend of ethanol. What else can I do? The rebuild kit is $80, and the gasket kit is $10. I was hoping I could just get away with the gasket kit.

 

[bassboy1]

For cleaning,a carb gasket kit,but it's always good to have a rebuild kit on hand while cleaning.Never can tell when you may find something bad or broken.I should have asked.Have you been using the low grade gas with ethanol blended in?Ethanol has a bit of water mixed in and can sometimes fowl things up.Not to mention that ethanol breaks down gaskets,rubber, and plastic parts.

Yes, the only gas I can get here in NJ has a 10% blend of ethanol. What else can I do? The rebuild kit is $80, and the gasket kit is $10. I was hoping I could just get away with the gasket kit.

I would start with the gasket kit. The rebuild kit will contain stuff that probably isn't worn out. Such as needle valves and seats, floats, high and low speed jets etc. Chances are a good cleaning and fresh gaskets (always a good idea whenever you disassemble a carb), and you are good to go.

What exactly does the carb rebuild kit for that particular motor come with? That sounds steep to me. Of course, I am a J/E guy, so it may be that Merc has a different markup, or specialty parts in there that I am unfamiliar with, but I have never seen a rebuild kit for a single barrel carb be over 30 bucks. Heck, the complete kits for each double barrel carb on a V6 Johnson (150 hp or higher), only run 35 bucks or so, and not only are they double barrel, they are much bigger than yours.

 

[Loggerhead Mike]

it sounds to me like you have too much fuel getting in there since it wont start choked and has a ruff idle. what color is your plug after you run it? a pic would be better. when its in a barrel the motor isnt under as much load as it is pushing your boat.

take your carb off and let the gas drain out. gently blow threw the gas line. should be clear. flip the carb upside down and gently blow. shouldnt be able to push any air threw (float valve sealing) . if thats fine i wouldnt rebuild the carb YET. i would get it running in the barrel, and disconnect the fuel mix and idle knobs so you can turn the jets completely in and completely out. start with leaning it out. rember when you turn the jet it wont affect it immediately. it has to burn all the gas out of the crank first. if that doesnt get you anywhere i'd replace all of the needle seats or a full carb kit

 

[danw77]

So what's the deal with the ethanol? How harmful is it and what can I do about it?

 

[ben2go]

Ethanol breaks down gaskets,rubber,hoses,and some plastics.The older they are the faster they break down.I use higher grade gas to avoid the problem.Ethanol can bring water in with it.I'm not sure if there are any sure fire additives that will take care of the ethanol issue.

 

[danw77]

By higher grade, do you mean like "Super" of "Plus" instead of "Regular"? I thought they had ethanol in them as well.

 

[Captain Ahab]

The ethanol question can go on forever - I have (knock on wood) never had an issue. I woudl try some "fresh gas" when you do all of the above steps

Still do not think that it will solve you reverse issue - but you need the engine to run well at idle to see

 

[ben2go]

By higher grade, do you mean like "Super" of "Plus" instead of "Regular"? I thought they had ethanol in them as well.

Yes.In my area ethanol is in E85,87,89,90 octane.The only ones without ethanol are 91,92,93 octane.Usually 91 octane and higher is usually considered premium.

 

[danw77]

OK, so I didn't get as much time to work on it this weekend as I would have liked. I did manage to get it out on the lake with the kids. We gave it a good run, and it seems to be clearing up. I'll still pull the carb off and clean it, but I was able to get it to run forward/reverse/idle with no hiccups. Seems to be idleing a little low still, so i'll look into that. The longer it runs, the smoother it seems to get. It still won't run with the choke on though. I did get back in touch with the guy I bought it from and he told me that he didn't clean out the carb (could have sworn he said he did, but whatever). I'm hoping to at least get to pull the plugs in the next day or two and see what they look like. I'll post up some pics when I do.