www.iFourWinns.com

Just an update for anyone searching the forum.

Shortly after this fix the fuel pump failed. While it took a bit of head scratching to troubleshoot it was a pretty easy fix once narrowed down.

I was hoping after all this the engine would be happier...no pinging, Dieseling etc but it wasn't.

(symptoms were an impressive run-on / dieseling after working the boat hard...towing a skier/tube)

So on a hunch I picked up some octane booster and it solved all my woes. (Promptly followed by a chewed up impeller and warmer than normal motor ... but that's another story...lucky for me I am a gauge watcher and caught it running warmer before any damage was done)

So for anyone watching...what does this mean (octane booster helps motor) I keep it on the water so getting higher octane fuel not an easy option but an additive is simple if not expensive ($12 for the bottle from local napa store) Is this symptom of timing being slightly off or a poorly tuned carb? Reading other forums it seems adjusting the octane is a common fix but I wonder if its just masking/correcting an underlying problem, seems to me these engines should be happy on 87/89 regular gas. Although I have no idea what the marina sells I'm sure its not above 89.

thanks for looking and any thoughts or opinions welcome.

_________________
Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT

untitled-545 by millerjont, on Flickr

On my OMC it gave 2 different timing specs (1* BTDC if using regular gas, 6* if using premium gas). Since all the gas docks here sell 93 octane I always set it at 6*. You can just use the octane booster but if you don't want to you could try retarding the timing a little at a time till the pinging stops. The underlying cause for both pinging and dieseling is carbon build up. You can do a compression test to verify this though. Hot comp test results of 185-200 psi woukd suggest that and there are ways to reduce the carbon build up with additives for the fuel system (Yamaha sells a good one called Ring Free).

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

BTW I had a 1970 Ford Torino many years ago with the 302 (5liter) with an Autolite 2100 2bbl carb. The auto choke did not open as it should and this caused considerable carbon build up. This engine pinged and deiseled even on premium gas. I had to retard the timing all the way to TDC to stop the pinging. So someone turned me on to GM Top Engine cleaner. This stuff was a very strong cleaner that you poured in the carb at fast idle. First I fixed the carb. Then I poured this stuff a little at a time at fast idle. There was a snow bank behind the car since it was mid winter. It smoked like mad & there were chunks of carbon in the snow when I was done. And no more pinging! Being a '70 it had a high compression ratio to start with.....

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Can't pre-ignition ( pinging/knocking) be caused by things other than carbon? While I agree a carbon deposit would cause a hot spot......my (lack of ) knowledge base begins with aviation engines which are much older simpler technology. But if modern cars solve these problems with retarding the timing I doubt they all have carbon issues ?

I'm not gonna mess too much with it when it's on the water but it's an interesting discussion for me as I continue to learn this boat..

_________________
Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT

untitled-545 by millerjont, on Flickr

Your original post in this thread led me to believe "Lean Mixture" for two reasons:
- Lean mixture can cause the hot spots (including hot electrode on spark plugs) that can cause the dieseling.
- You said you needed to keep the engine at 1500rpm or so for a while after a cold restart.
I'm thinking a carburetor rebuild kit is in order.

FWIW, I run 87 octane all the time without a problem. I only got dieseling one time when I came off a plane and shut off immediately. As long as I idle 10+ seconds before shutting down, it never runs on.

_________________

"Knot Easy" 2000 Horizon 240 Volvo 5.7GS /SX
tow: 2017 Honda PILOT EXL-AWD
prev. boats:
'87 Chaparral 198CXL 4.3 OMC Cobra
'69 Jetstar 16ft Ski Boat, 115hp Yamaha
'68 Aluminum Jon Boat, 3hp Sears
'64 Water Wings

Lean mix for sure is a cause, but the plugs in the pix, did not look like the mix was lean, more the other way around. Try posting up a better close up pic if you take em out again. Another factor is the heat range of the plug. Due to differences in the center insulator, some plugs will run hotter (to burn off deposits) or cooler (to prevent pre-ignition). Make sure you are using the right marine plug (AC Delco MR 43 T has always worked well for me) in that engine. Plugs for an auto application may be wrong for marine operating conditions.

_________________
88 Four Winns 200 Horizon
4.3 OMC Cobra-4bbl
2002 Walker Bay 10/2012 Suzuki 2.5
2008 Walker Bay 8

1998 Jeep Grand Cherokee 4.0/Selectrac
2007 Jeep Grand Cherokee 5.7 Hemi/Quadradrive II

Those plugs were tossed and replaced with Volvo penta plugs .... don't recall what brand they used but will check....we're pre-gapped, though no I have old plugs and will look....came as a kit with new wires, rotor and cap.

With the higher octane it seems to be starting better too and no more deiseling.....will try and listen for pinging when I take it for a run today.

Will inspect plugs end of season too

_________________
Jon Miller
1998 four Winns Horizon H200
Volvo Penta 4.3 GL
Newtown, CT

untitled-545 by millerjont, on Flickr