INDMAR 5.7 CARB IDLE/BOGGING ISSUES 2004 XLV Throttle Position Sensor?

[OJT23]

So I finally got the boat back out on the water after some fiberglass work. Boat ran great all day (5 hours) until it came time to put the boat back on the trailer. Putting back to the ramp, the engine began idling high (around 1800) and I had to shut it off and restart to get it back down to 800 or so RPMs. Then the boat started bogging down when I accelerated past idle. Half the time it would die once I move the throttle past idle. If I floored the throttle, it would bog down momentarily and then accelerate. When at plane speed, the boat would then bog down and I would have to return it to idle/neutral to prevent it from dying. Restarted fine every time, but issues remained. I had a new fuel filter in the boat, which I replaced on the spot. Same symptoms.

Took it to my repair guy and he said it badly needed a tune up (Boat dealer I bought it from said it just had one done...ugh.) and that the computer was compensating for the corroded rotor and distributor cap, and plugs needed replacement. Showed me the parts, yes, they needed replacement. Got the tune up done and it ran great again, for a few hours. After about 2-3 hours on the water, it started doing it again. Putted back to the ramp and put the boat up on the trailer.

Anyway, after reading a few posts on here and on the Supra forum, it looks like the TPS (Throttle Position Sensor) is the culprit. Erratic idle, bogging down, etc...seems to be the common theme among those who replaced the sensor with successful results. I bought one at Pep Boys for $36 (told them it was a 1999 350 Chevy 5.7 engine) and I'm going to give it a shot. In case this doesn't work, anyone else have any suggestions?

Thanks in advance for your responses.

[BensonWdby]

I wonder if this might be the vapor lock problem several folks have discussed on this forum? Not a motorhead so that is the extent of my input on the mater.

[OJT23]

Good point. I did buy a new anti siphon valve and will install it with the tps. I heard that you can open the gas cap while having vapor lock to test and see if thats the issue. If it alleviates the problem then problem solved?

[kaneboats]

That won't do it. You have to cool the fuel that is evaporating. Pour cold water on the fuel pump.

[motosno963]

have yall seen the vapor lock kit that bakes online sells? i dont know if it would salve the problem for our vapor lock but if you have the money why not? mine does the bog as well and im thinking about getting the oil pressure switch. if i recall someone stated that could have been another issue with the bog as well..i dont remember where on here i saw it
http://bakesonline.com/detail.aspx?ID=2903

[Stazi]

Was the inline fuel filter changed during the tune up?

[OJT23]

Thanks for the inputs. I replaced the fuel filter with same results. Not sure if it's vapor lock, but the temp was pretty low, somewhere around 160-170. Not sure if that matters. Also, it was overcast, so not too hot outside.

Will install the TPS Friday and check again!

Thanks!

[saskyrider]

My boat started to do this when the oil pressure safety was starting to fail... I know it sounds silly but check that as well. Its a safety that shuts off the fuel pump when it doesnt sense oil pressure.

Sent from my apple crushin android device

[motosno963]

my question is, do u have to change the oil when you do the safety switch?

[greghen]

I'm having some similar issues with my 06 lsv. Could not go above 1,000 Rpms without it staling. Brought it into the shop they tuned the carb. Just back on the lake and it ran better but still hesitates or stalls when I star out of the hole. I'm interested in if the tps solves your issue