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MNbu

86 Malibu Skier running rough

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MNbu

I bought a 86 Malibu Skier last fall and first time out in ran pretty bad, I started with getting old fuel out, changing fuel/water separator, quick carb clean, new plugs. It has a new distributor, and plug wires. I took it out again, and it ran better, but same outcome. After about 10-15 minutes of it running good it started to hesitate, sputter, and backfire.  Eventually it just died completely and wouldn’t start again. It runs great on a hose in the driveway, but it seems like when it’s under load it gets angry. It was late in the season so I just put it in storage. I brought it to MN inboard and had them look at it, they looked it over, and compression was good, timing was right. The only thing they found was the wrong fuel pickup, and no anti-siphon. Unfortunately the ice just went out today, so they couldn’t lake test it a month ago.  Thinking that might have fixed it I took it out today, it ran way better than it did last fall, I got it up to 40 and it felt really strong. But after 20-25 minutes I had the same result, hesitation, sputtering, backfiring, and could only get up to about 15 MPH. I limped it back to the launch, and have no idea where to go with it next. Any ideas, advice, pointers would be greatly appreciated!!

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minnmarker

Choke?  Wire it open when you get the engine warmed up?

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MNbu

I will give that a try tonight, thanks for the reply!

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96Response

You, may want to check the coil. I have seen this before more than once. The coils go bad inside and build up internal heat. They will be fine for a while then all of sudden they just cut out. When they cool down then they work again. Very inexpensive to replace, $20 part. 

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MNbu

When I bought the boat I was told the whole ignition system was new, but who knows how accurate that is. I will pick one up and try it! Thanks for your response, I really appreciate it!

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MadMan

It's always difficult to diagnose if the problem is fuel or ignition related.  Backfiring usually indicates a lean condition.  Maybe you could "T" in a fuel pressure gauge between the pump and carb and see what's going on when the problem occurs.

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Rednucleus

How old was the old fuel?  Maybe fresh tank with your favorite stabilizer added, change filter again; check carb bowl for debris; maybe carb needs a clean/rebuild

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martinarcher

Another vote to keep an eye on that coil.  I keep a backup on board.  If it dies when warm and runs fine cold that's a tell tale sign.

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electricjohn

If you have an HEI ignition system, I would take a good look inside the distributor.

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MNbu

Thanks for all your help guys! I changed the coil and tried to wire the choke open. It definitely ran better, but still had a lot of hesitation after about 20 minutes of run time. Going about 35 MPH, I could feel it hesitate and sputter, kind of jerky like I was letting off the throttle for a split second and then getting right back into it. I’m gonna try to burn through the rest of this fuel and hope that has something to do with it, there was probably a half gallon leftover of bad fuel mixed with the 10 or so of fresh I put in. 

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minnmarker

Try soon HEET. Could be water in the tank - but I doubt it.  As said above, maybe distributor? An 86 probably doesn't have a knock sensor?

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Lanman

Check to see if the rotor is installed correctly. When I replaced mine, it didn’t go down on the shaft far enough and caused issues like this after it heated up. Cleaned up the shaft with Emory cloth and she slipped right on.

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MNbu

Thanks again for all the help and suggestions guys. I’ve tried all the things you guys have suggested with no luck. Last time out after a new coil it only ran for about 10 minutes then died. I haven’t been able to get it started since, it won’t even try to turn over, nothing happens at all. When I pump the throttle I see no fuel going into the carb at all. So I’m wondering if it could be the fuel pump that’s causing my issues? The only thing that doesn’t make sense is that I’m not getting anything when I try to start the engine, it would try to crank still with a bad pump right? 

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Rednucleus

If it's fuel pump you should be able to spray fuel down the carb and get it to fire.  When you say "try to crank",  do you mean fire?  Mechanical fuel pump, correct?

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MNbu

Ya, I meant try to fire. Yes it is a mechanical pump. 

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Woodski

@MNbu:  Your symptoms indicate a couple of things - 1.  as heat builds up under the dog house that causes some component to fail (coil a likely candidate as noted),  2. as fuel is burned a vacuum is created in the system not allowing the carburetor to get enough fuel supply (anti siphon valve (not likely per your comment), a weak fuel pump, blocked or leaky fuel pickup tube or tank fitting)  3.  lack of fuel in carb to keep the boat running (low float level due to debris, improper setting, binding in the down position).

Your last comment certainly points you towards the fuel side as no fuel from the accelerator pump as you give the throttle a twist.  Yes on turning over given that age boat, probably no defeat device in system to thwart your troubleshooting.

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justgary

Definitely test the fuel pressure at speed.

And you mentioned a "quick carb clean."  It's probably time to do a full carb rebuild so you know that you have good seals and clean jets.

Oh, and I have had fuel line go bad due to ethanol fuel.  This was on a riding mower.  The thing drove me crazy since the fuel would flow fine at idle, but a chunk of the hose had come off inside and created a sort of pressure valve that would only close at higher fuel flows.  I discovered it when I removed the tank end of the line so I could blow the line clean, but soon learned that I could blow gently just fine, but it would stop as I increased pressure!  Maybe change your fuel lines.  In an '86, it's time anyway.

- Just Gary

 

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tvano
1 hour ago, justgary said:

Oh, and I have had fuel line go bad due to ethanol fuel.  This was on a riding mower.  The thing drove me crazy since the fuel would flow fine at idle, but a chunk of the hose had come off inside and created a sort of pressure valve that would only close at higher fuel flows.  I discovered it when I removed the tank end of the line so I could blow the line clean, but soon learned that I could blow gently just fine, but it would stop as I increased pressure!  Maybe change your fuel lines.  In an '86, it's time anyway.

- Just Gary

 

Most manufacturers advise replacing gasoline fuel hose after 10 years" per boatus. some differing opinions here, naturally, even within the boatus community. 

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Rednucleus

Does this motor have an ignition control module in the distributor - common part for heat associated problems. Easy inexpensive change to try if it has one.

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916Skier
On ‎5‎/‎2‎/‎2018 at 12:29 PM, martinarcher said:

Another vote to keep an eye on that coil.  I keep a backup on board.  If it dies when warm and runs fine cold that's a tell tale sign.

Bringing this thread back to life. Similar issue on my 85 skier. The coil you guys are talking about which one is it? Everything I see online is $60+ no the $20 some people are saying

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916Skier

Where and what does this $20 coil look like? everything is see online for my 85 skier is around $60

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JasonK

It's prob $60. Looks like a small pop can, prob black, in a bracket next to the distributor.

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martinarcher

This is the one I run.  They see to last longer than the Accel coils for me.

 

 

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MNbu

Figured I would post on this since I started the thread and give an update, hopefully it can help. I ended up rebuilding the carb and that never solved the problem, probably good to do anyway. I pulled the spark plugs again and looked them over, and sure enough porcelain was cracked. I then thought I would look at the distributor cap and at that same cylinder there was a tiny crack and a lot of carbon tracks. Replaced that cap and got some new spark plug wires and that fixed it. Very cheap and simple fix. It has done it a couple times since and I’ve just replaced the cap again. 

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