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View Full Version : Rough idle and boat stalls/backfires


wakerGreg22
09-10-2005, 08:55 PM
I have a 1987 tristar 190, i just bought it about a month ago. The first time i took it out it ran great, but know it idles rough and it pull out of the hole fine but after about 45 seconds it starts slowing down and backfires. i have changed the plugs, wires, cap, rotor, fuel filter, and i took the bowls off the carb and found them to be clean. i just want to enjoy my boat any ideas

Storm861triple
09-11-2005, 03:01 PM
You're running out of fuel. Put a fuel pressure guage on it and post back as to teh FP reading under WOT and idle.

-Tom

PendO
09-11-2005, 03:34 PM
I have a 1987 tristar 190, i just bought it about a month ago. The first time i took it out it ran great, but know it idles rough and it pull out of the hole fine but after about 45 seconds it starts slowing down and backfires. i have changed the plugs, wires, cap, rotor, fuel filter, and i took the bowls off the carb and found them to be clean. i just want to enjoy my boat any ideas

were your problems manifesting before you replaced the plugs and wires ... I thought there was a recent thread about a person having a problem with a late model M/C that had the plugs not connected in the proper firing order?

Storm861triple
09-11-2005, 04:37 PM
If the problem were w/the plug wire orientation, then it would run poorly all the time; not after 45 seconds.

Check the fuel pressure.

-Tom

PendO
09-11-2005, 04:43 PM
If the problem were w/the plug wire orientation, then it would run poorly all the time; not after 45 seconds.

Check the fuel pressure.

-Tom

yer right, still, I wonder when the problem manifested.

wakerGreg22
09-12-2005, 02:25 PM
the first two times i took the boat out it ran great, and then the third time it started doing this his is when i changed plugs i will check the fuel pressure. what pressure is it supposed to read, and what does WOT stand for. i didnt mention in my first post but it does it real bad in turns. Also i seem to loose a little power when i turn is this normal.

Thanks for the input. this site is great

Storm861triple
09-12-2005, 03:01 PM
WOT= Wide open Throttle.

Fuel pressure should be somewhere between 4-6 PSI. It really only needs 1 PSI technically; it doesn't run in fuel pressure like an EFI engine, the fuel pressure just keeps the bowl full. If you any pressure at all, then that is enough to keep the bowl full at that given throttle setting. Over 7 PSI can give you issues, as it starts to push the fuel past the needle and seat when it shouldn't.

The boat sill slow through corners. The engine shouldn't "loose power", but the boat will slow and "dog" the engine some, as there is more resistance/friction when turning.

What did you set the gap at when you changed plugs?

-Tom

wakerGreg22
09-12-2005, 04:41 PM
i set the plug gap at 0.35 which the engine owners manual says. i will hook up a pressure gauge and post findings.

Storm861triple
09-12-2005, 06:57 PM
i set the plug gap at 0.35
O.K., Good. :)

-Tom

wakerGreg22
09-19-2005, 02:10 PM
the fuel line is a hard steel line how do i hook a gauge up to it

Storm861triple
09-19-2005, 02:22 PM
You'll have to get a flaired fitting (pipe) and flair nut (from any decent auto parts store for a few cents) that will fit into your carb. Cut the new pipe so it's about 2" long coming out of the flair nut. Then push a piece of 3/8" fule hose over the end of it, and over the end of your existing fuel delivery line. Cut the hose in the middle and insert a "T". Stick another pice of hose on the nipple and to your gauge, then hose clamp all of it. Start it up and run it and watch the gauge. ;)

-Tom