- Jul 10, 2020
- 161
- Boat Info
- 1981 310 Vanguard Express
- Engines
- Twin Mercruiser 6.2 MPI Horizon FWC inboards
This season is turning into one of those one step forward, two back deals.
Recently I changed out the IAC muffler on both my engines which immediately and comfortably solved a low idle and stalling under load at idle issue I was having. That was 3-4 running hours and about 3 weeks ago (we're weekend boaters mostly).
Now both my engines, with new IAC mufflers and clean flame arrestors, are idling roughly. They run fine and smooth at 1,000rpm+, but idle is poor. It's jerky and irregular sounding, almost like a misfire, and is quite low on cold start. Starting is also more difficult than it used to be - in fact yesterday the port engine would only crank half a turn initially, really struggling, until I switched batteries over (and then it cranked ok when I switched them back after it started). The idle can be made to improve by running the engines at 2000-3000rpm in neutral for a few seconds and then bringing it back down to idle, then it's smooth and normal, until a restart.
I can hear the IAC sucking hard if I remove the muffler (which increases idle speed a bit as you'd expect).
I've changed fuel filters (inline and water sep); gas looked pristine with not a drop of water in the filter. (I find this slightly suspicious but there we are - if it's not in the filter, it's not in my engine.)
I'm noticing also some slight hesitation when advancing the throttle on both engines. Say from 1000 rpm, I push the lever forward a bit, then revs drop to maybe 900 for a half second then go up to where you'd expect from the throttle position.
So my plan is:
- Remove and clean each of the IACs in case they're only opening part way.
- Inspect the distributor caps and rotors for wear and corrosion
- Check fuel pressure
- Put my fingers against each of the injectors and see if I can feel them pulsing
- Check the engine grounds with a multimeter and inspect all the ground cables to the battery banks for corrosion.
What else should I add to my list of things to check?
It's super weird that both engines are developing a similar fault. I'm almost tempted to blame the fuel I recently added, but it looks and smells fine and it's a very, very busy gas dock. The hot weather too, maybe a factor?
I'm not going to start plopping parts in with no justification. I'm on the fence about investing in an Rinda, too. I think that might get me some answers quickly.
Frustration grows here.
Thanks for any advice!
Recently I changed out the IAC muffler on both my engines which immediately and comfortably solved a low idle and stalling under load at idle issue I was having. That was 3-4 running hours and about 3 weeks ago (we're weekend boaters mostly).
Now both my engines, with new IAC mufflers and clean flame arrestors, are idling roughly. They run fine and smooth at 1,000rpm+, but idle is poor. It's jerky and irregular sounding, almost like a misfire, and is quite low on cold start. Starting is also more difficult than it used to be - in fact yesterday the port engine would only crank half a turn initially, really struggling, until I switched batteries over (and then it cranked ok when I switched them back after it started). The idle can be made to improve by running the engines at 2000-3000rpm in neutral for a few seconds and then bringing it back down to idle, then it's smooth and normal, until a restart.
I can hear the IAC sucking hard if I remove the muffler (which increases idle speed a bit as you'd expect).
I've changed fuel filters (inline and water sep); gas looked pristine with not a drop of water in the filter. (I find this slightly suspicious but there we are - if it's not in the filter, it's not in my engine.)
I'm noticing also some slight hesitation when advancing the throttle on both engines. Say from 1000 rpm, I push the lever forward a bit, then revs drop to maybe 900 for a half second then go up to where you'd expect from the throttle position.
So my plan is:
- Remove and clean each of the IACs in case they're only opening part way.
- Inspect the distributor caps and rotors for wear and corrosion
- Check fuel pressure
- Put my fingers against each of the injectors and see if I can feel them pulsing
- Check the engine grounds with a multimeter and inspect all the ground cables to the battery banks for corrosion.
What else should I add to my list of things to check?
It's super weird that both engines are developing a similar fault. I'm almost tempted to blame the fuel I recently added, but it looks and smells fine and it's a very, very busy gas dock. The hot weather too, maybe a factor?
I'm not going to start plopping parts in with no justification. I'm on the fence about investing in an Rinda, too. I think that might get me some answers quickly.
Frustration grows here.
Thanks for any advice!
