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Monsoon 320 bog, surge, die only after warm.. PLEASE HELP,


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Okay Malibu experts, yet another bog, surging, dying question for you. I've read every post about the topic and found very helpful topics, and worked through many of them.

Boat Background:

1998 Sunsetter VLX w/ monsoon 320, I believe it's fuel injected (see pictures)

104 hours (not a mistype) It was stranded on a dock for 10 years! Please no need to comment on the waste of this. It's my dad's boat and he never bought a trailer for it, and we couldn't get it off the dock anyway.

Situation as detailed as possible:

Drop the boat in the water, starts at first or second crank. Idles beautifully. throw it in gear smooth riding at idle to 2000-2200 rpm. Slowly accelerate approaching 2500-3000 rpm (or a little less) , bogs down while losing power. no response from throttle until I back off of it. when motor is cold I can save it from dying out by pulling back on throttle. When warm it will bog down then sputter dead.

start it back up put it in gear cruise on lake at 2000 rpm without problem for about 5-10 minutes. then begins to surge slightly, and increases to surge more, then dies out. (by surge, i mean at same throttle position, power decreases slightly then try's to return to same rpm, in a repeated fashion. I don't know if i'm using this term correctly) Place gear in neutral, and I can rev it to 5000 rpm without a problem

I have difficulty restartin after the point of it dying out on me. some times one crank right back, and other times waiting a few minutes. Either way when it's warmed up it's harder to restart. Also when warmed up and I restart it doesn't like to idle anymore. I have to run it at 2000+rpm to keep it from dying out.

What I've done:

After reading tons of posts on the subject matter and trying many of the cheaper fixes this is what I've done.

  1. drained gas, new premium gas with octane booster
  2. changed spark plugs autolite platinum (someone suggested these plugs could be the problem, what's your take?)
  3. changed oil and filter
  4. changed both fuel filters (probably going to do this again, just in case)
  5. changed impeller (old one was destroyed)
  6. cleaned waterhose from pump to tranny (did not see a screen in there)

Suggestions from other posts

  1. fuel pump - seems to be in good working order, no whining noises, and pressure at the fuel rail bleed valve seems strong, however did not use
  2. pressure gauge to check.
  3. sensors, knock, iac, etc - I would be willing to change these is you can give me part numbers, and how to change them. I shop at "west marine"
  4. thermostat - after changing the impeller, temp stays at 140, but then again I can't run it longer than 15 minutes to see if it get hotter. before
  5. impeller change I was reaching almost 200 degrees with same 15 minute run time.
  6. vapor lock- doesn't seem like the issue, but i let it cool after it doesn't start back up, and my percentage of start up increases with the longer I wait.
  7. fuel seperator- drained gas and put fresh gas in, doesn't seem to be the problem.
  8. running rich - it smells a little rich, but I don't know how to adjust this (please advise)
  9. air/fuel mixture - i think this goes back to some sensors, can't check.
  10. throws a code - can someone tell me where the data plug is located , a buddy of mine has a comp.
  11. thermostat - how can i check if this is bad? which thermostat would I buy? 140 or 160 degree I saw two or three at west marine to choose from.

I've included pictures of motor, and have arrows which points to different sensors and motor parts. if someone can answer what part goes to what point, I can update the image, and it can be used as a reference for other's to view. THANKS!

Oh and I have a hissing (vacuum like) noise coming from the carb, that I pointed on the image. it hisses at idle and goes away at higher rpms. is this normal?

And I have a leak on the image, can I just remove the hose and tighten this down? or do i have a serious problem.

Okay I know this is long, but I wanted to be very detailed, and I hope future people with problems can be referenced to this post with all of you guys' help.

Image links:

I WILL UPDATE THESE IMAGES AS I LEARN MORE

MONSOON IMAGE (YOU MAY LINK TO THIS IMAGE FOR OTHER POSTINGS IF NEEDED)

SAME AS ABOVE DIFFERENT SIZE

Edited by royeh32
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Try replacing the cap and rotor..... www.skidim.com

Thanks, I'm considering ordering a new cap, rotor and plug wires. But it seems to be firing properly, would these items cause it to work at idle and neutral, but squander when in gear at 3000rpm?

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Change Dist. Cap and Rotor most definately. Right now.

Hook up a mechanical fuel pressure gauge and see what the pressure is. This is the only way to eliminate it as a variable.

You say you drained gas - this is from the tank? If not, Pump fuel tank dry and replace with new.

If you have a fuel/water seperator, replace it.

Let us know if any changes after this.

Peter

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Cap & Rotor corrosion will most definitely show up at either higher RPM or under heavy acceleration.

Overall, this sounds like a fuel issue... A fuel pressure gauge would tell you.

First recommendation would be to replace filters, but you already did that.

It could also be stuff from the tank that got past the filter trapped at the fine screen that's on the inlet of the fuel pump. Several here have had problems with that.

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I have no idea, but, you don't have a carb. That's your throttle body.

And check your trans cooler. That's where old impeller pieces get stuck, which restricts water flow and could be your problem. You note you didn't find a screen. My trans cooler has a honeycomb type structure in it that traps old impeller pieces.

I think you could be dealing with a cooling issue, which might put the motor into limp mode, if it has one. I don't have experience with old fuel injected motors.

What does your temp gauge say when it's warmed up and won't start? or when it hesitates at idle.

If you start it cold and let it idle, what does the temp gauge do? rise to 140 and then fluctuate right around there? If the thermostat works, the temp rises and falls around 140. mine fluctuates between 140-150 when warm.

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thank you guys for the quick reply. looks like you are all determining fuel or cooling issues, which was where I was leaning. I'm going back out the boat tonight to check some things you suggested.

I'll check:

screens for fuel lines near inlet of pump

screens at the trans cooler.

purchase fuel pressure gauge (what should my pressure be? do i hook it up to the fuel rail bleed valve or inline?)

cap and rotor (how much and what's a good aftermarket brand for our indmar?)

jasonk: starts cold rises to 140 and stays around there. temp says 140 when i have hard time restarting and/or idling.

thanks guys keep the suggestions coming.

Edited by royeh32
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thank you guys for the quick reply. looks like you are all determining fuel or cooling issues, which was where I was leaning. I'm going back out the boat tonight to check some things you suggested.

I'll check:

screens for fuel lines near inlet of pump

screens at the trans cooler.

purchase fuel pressure gauge (what should my pressure be? do i hook it up to the fuel rail bleed valve or inline?)

cap and rotor (how much and what's a good aftermarket brand for our indmar?)

jasonk: starts cold rises to 140 and stays around there. temp says 140 when i have hard time restarting and/or idling.

thanks guys keep the suggestions coming.

Cap and Rotor are from a Chevy 350. Head to your local Napa/Autozone/Murrays and they will have them in stock. Nothing special about them for the engine.

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Mine ran fine until 3250 rpm's.....bogged down and stumbled, sounded horrible. definitely cap and rotor. Easy fix.

Edited by rater1979
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We had a similar problem with my brother's 97 Monsoon.. Finally took it to a shop and hooked it up to find 2 injectors were bad... Replaced and it runs like new...

I would add INJECTORS to that list of possibilities although I don't really know how to test them without hooking up to a computer.

Good Luck

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UPDATE: decided to take to my local malibu dealership.

They said the ECM is bad, which is what I didn't want to hear...

The computer was throwing a code for bad throttle position sensor, but the service manager says it's not receiving any signals from the other sensors. I guess it should be sending 5 volt to and from sensors.

The ECM for a MEFI 2 costs $1346, not including labor. What do you guys think? Is it worth it?

He did find broken pieces of the previous impeller at the tranny cooler. He went through all the electrical wiring, and found out that was where the problem was.... at the ECM. :(

Edited by royeh32
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Is it worth it, no. I think you should donate it to one of us and just rid yourself of the problem. Sorry couldn't resist.

Yes, it is worth it. I personally would be looking for a cheaper place to buy the ECM, and replace it yourself. Just unplug all the wires, and plug in the new one. Someone on here has to have a connection to buy one from. I would also run some fuel system cleaner through to get the varnish out of the injectors, replace the cap/rotor, and plugs with AC-delco, or NGK plugs. In the ned you spend $1,000 or so, and end up with a very low hours Malibu boat. Sounds like a good deal to me.

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In your picture

Point C if it has a vacumn line hooked to it is the fuel pressure regulator

Point D is MAP(Manifold Absolute Pressure, or atmospheric pressure) sensor

Point E looks to be throttle position sensor

Point F is fuel injector

Your second point F(one most to the left) looks like water temp sensor

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  • 2 years later...

I just started having a similar problem on Sunday when I was out pulling mu daughter on the tube with my '99 Sunsetter VLX. It was running fine so far this season at high rpms but on Sunday when I would start up it powered fine until 2500 rpm but as I tried to give it more throttle it started to bog down and if I didn't back off right away, it backfired. I was reading this post and am hopeful that a bad cap and rotor is the closest match. My question is does the 1999 VLX have the Monsoon 325 and is the cap and rotor parts the same as the 350 Chevy cap and rotor?

Thanks in advance for any help you can give.

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I just started having a similar problem on Sunday when I was out pulling mu daughter on the tube with my '99 Sunsetter VLX. It was running fine so far this season at high rpms but on Sunday when I would start up it powered fine until 2500 rpm but as I tried to give it more throttle it started to bog down and if I didn't back off right away, it backfired. I was reading this post and am hopeful that a bad cap and rotor is the closest match. My question is does the 1999 VLX have the Monsoon 325 and is the cap and rotor parts the same as the 350 Chevy cap and rotor?

Thanks in advance for any help you can give.

I think any cap and rotor for a chevy 350 works. I used Accel part number 8132 on my 2000 Monsoon. The EFI Monsson was used in 1999, but I believe a carbed version was also available. I'm pretty certain if you have fuel injection, the Aceel number I listed will work.

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I think any cap and rotor for a chevy 350 works. I used Accel part number 8132 on my 2000 Monsoon. The EFI Monsson was used in 1999, but I believe a carbed version was also available. I'm pretty certain if you have fuel injection, the Aceel number I listed will work.

Thanks. Were your bogging symptoms the same as mine? Did you replace anything other than the cap and rotor? I looked back at my last dealer maintenance and saw that they replaced the fuel filter which I though might have been the original problem after reviewing this forum post. Just curious and thanks again for the reply Deck Hand!

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I have no idea if this boat has the same torpedo fuel pump that my friends 05 Supra has, but there was a really fine screen on the inlet of the fuel pump that had gotten gummed up. He pulled the screen, blasted w/ pb-blaster and removed all the junk on it, and has been running fine since.

He could idle all day, no temp issues, but couldn't run more than about 3000 rpm. Good luck!

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Thanks. Were your bogging symptoms the same as mine? Did you replace anything other than the cap and rotor? I looked back at my last dealer maintenance and saw that they replaced the fuel filter which I though might have been the original problem after reviewing this forum post. Just curious and thanks again for the reply Deck Hand!

My boat was running fine before I replaced the cap and rotor. The boat is new to me and although I am pretty confident it was well cared for, I went through and did a nice tune-up on it before the season started just for my own peace of mind.

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My boat was running fine before I replaced the cap and rotor. The boat is new to me and although I am pretty confident it was well cared for, I went through and did a nice tune-up on it before the season started just for my own peace of mind.

Replaced the cap and rotor and also the plugs. Checnged out the fuel filter by the tank and still bogs at 3000 rpms. I'm going to check the fuel inlet screen and add some seafoma and spray the air intake with choke cleaner. The next thing on my list would be wires / fuel pump? There is a wining sound but it's always whined somewhat. I saw a post on here about replacing the fuel pump and also a post about the MAP sensor. Any other ideas would be helpful. Heading back out to the lake now.

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  • 3 weeks later...

Replaced the cap and rotor and also the plugs. Checnged out the fuel filter by the tank and still bogs at 3000 rpms. I'm going to check the fuel inlet screen and add some seafoma and spray the air intake with choke cleaner. The next thing on my list would be wires / fuel pump? There is a wining sound but it's always whined somewhat. I saw a post on here about replacing the fuel pump and also a post about the MAP sensor. Any other ideas would be helpful. Heading back out to the lake now.

Update: I replaced the cap, rotor and plugs and it still booged down at 2500rpms. I added a few cans of Seafoam and 10 gallons of 92 octane fuel and it was able to run at about 3500 rpms. I replaced the fuel filter by the tank and no difference. I tried to locate the screen at the fuwl pump inlet but did not see anything. Is it tucked away in there pretty deep?

The last thing to do is replace the fuel pump. I ran it around the lake and had a buddy spary carb / choke cleaner as I was bogging and it did allow me to get to 4500 rpms (took almost the whole can) so I'm thinking fuel pump? I called the dealer and they said $330 for the pump. I've looked on ebay and on the internet and can;t locate anything there. Any other thoughts?

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Update: I replaced the cap, rotor and plugs and it still booged down at 2500rpms. I added a few cans of Seafoam and 10 gallons of 92 octane fuel and it was able to run at about 3500 rpms. I replaced the fuel filter by the tank and no difference. I tried to locate the screen at the fuwl pump inlet but did not see anything. Is it tucked away in there pretty deep?

The last thing to do is replace the fuel pump. I ran it around the lake and had a buddy spary carb / choke cleaner as I was bogging and it did allow me to get to 4500 rpms (took almost the whole can) so I'm thinking fuel pump? I called the dealer and they said $330 for the pump. I've looked on ebay and on the internet and can;t locate anything there. Any other thoughts?

I was reviewing other posts related to fuel pump and was steered toward Jasper and found on there for $180. Shuold be here in a day or two.

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I was reviewing other posts related to fuel pump and was steered toward Jasper and found on there for $180. Shuold be here in a day or two.

Hallelujuh!!!

The Carter fuel pump came yesterday evening UPS and this morniong I went out armed with WD40 and a fist full of tools!

I found some encouragement on a few other post and although it was tough getting the old one out, it was easily swapped in afterward. The real trick was finding the right size hex key to remove the housing surrounding it. I turned the key and felt the new pump hum and did not see any leaking. I just took it out on the lake and it was immediately able to run up to 5,000 rpms. That's a few hundred more than it has run at in past years.

Thaks to everyone who has posted for all the help and wisdom. May God bless all of you and keep you safe this season!

Rockin LZ

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  • 9 years later...

It’s been several years since any of you posted on this thread but... I have a 1997 malibu sunsetter with the monsoon 320. I am currently having the same bogging symptoms listed above. I have replaced the ecm, cap and rotor, spark plugs, fuel filters and fuel pumps, map sensor, fuel lines. And I’m still getting a bogging. I’m stuck and have no idea what to do. ANY info would be greatly appreciated. 

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