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

[parrothd]

Yours is the accelerator pump.

Check to make sure it's squirting. This is only for the carb engines. Take the filter off and look down the throttle body, have someone move the throttle to wide open. You should see a small nozel shooting 2 streams of fuel. It should be very strong. On mine the spring/arm wasn't moving enough, I added a small spacer.

[OJT23]

Awesome....thanks...I will check the oil sensor and the accell pump. I will post my results once I get the boat out on the lake. going to get it out for a test run this weekend before the 4th gets here.

[zabooda]

My carburetor is in the shop getting a rebuild and I suspect it is the accelerator pump. It is the first trouble I've had in the 13 years I owned it.

[parrothd]

ON my carb if I went slowly too wide open throttle it ran fine, but if I tried to hit it hard or quickly to wide open it would stutter and stall...

[Stazi]

ON my carb if I went slowly too wide open throttle it ran fine, but if I tried to hit it hard or quickly to wide open it would stutter and stall...

That's an accelerator pump issue. You should adjust the pump lever connection poiunt to get it more stroke when you push the throttle forward.

[kaneboats]

You should be a Dr. for old guys. :o

[liquid_acid]

I had a similar problem on my outback. I took the cover off the carb and watched how it was working. Seemed that the floats were stuck so it was dumping too much fuel in the bowls at idle. When I gassed it, it flooded itself and took a few seconds to burn off all the fuel in the carb. I ended up rebuilding it and found that secondary jets were also pretty clogged. The carb was pretty dirty.
http://img.tapatalk.com/d/14/07/02/6ege6aga.jpghttp://img.tapatalk.com/d/14/07/02/aguzymym.jpg

Not sure if this helps your problem or not but might be worth looking into a rebuild.

[OJT23]

If the TPS doesn't solve the issue I'll check the carb. Life has been too crazy to get it out for a test run.

[OJT23]

Installed the tps and worked great for 45 minutes. After that, it was the same thing all over again. The temp got up to 190, not sure if that has anything to do with it. I let it cool off for an hour, but the temp never really came down. No improvement either. I wonder if the new tps is bad, I've heard of them having issues. Only reason I would suspect that is that it ran great for 45 mins. I think if it was a pump it would have not run well from the start. I was able to get about 2500 rpm out of it after jockeying the throttle a bit, fast enough to get back to the dock before dark. If it moved it from that setting it would want to die. Any thoughts?

[OJT23]

Hmm.. Just did some more reading. It seems like the fuel pickup tube could be the culprit. This may be the reason that it starts bogging down after a certain period of time. This time, it occurred at 1/2 tank full. Can't remember where it was at last time it happened. Anyway , probably not too expensive and worth investigating. Anyone ever replace on of these?

[OJT23]

May have figured it out. Pull the thermostat (160 deg) and tested it with 200 degree water. Didn't budge. I heard that temp gauges can be off by as much as 20 degrees. Wondering if the engine went into limp mode after hitting 180, which could actually be 200. It got to 190, which, according to my dealer is probably ok esp since it didn't run it long after experiencing the issue. Hope this is it, it would explain everything. Will report back.

[OJT23]

Thermostat didn't fix it. Ran cool though, between 160-175. Still think it may be the fuel pickup line, got one on order last week. I put six gallons of gas in the tank, which was already half full, to arrive at 3/4 full. The engine started bogging down right when it got to just above half full, just like the last two times. If i advanced the throttle above idle, it would bog down and die. The only thing a cracked or damaged fuel pickup would not explain was the occasionally high idle that would occur, along with surging RPMs. Would this be a symptom of a fuel starved engine? I know my weed eater will spin up just before running out of gas.

[parrothd]

Take it to the dealer and have them check the computer..

[OJT23]

Thanks..good suggestion. I think I may have figured it out though. Boat runs great when slightly above 1/2 tank or better. Bogging issues start when tank is at or below that level. I imagine they it's either the fuel pickup line or the fuel pump. I think that when the tank is full, it requires less effort to draw the fuel out of the tank. That's why I the it may be a weak pump. If not, the pickup line for obvious reasons. Has anyone ever removed the floor to access the tank?

[parrothd]

Why haven't you replaced the pump?

[OJT23]

That's the first thing I had checked. When i first experienced these problems, i took it to a mech. He tested fuel pressure for 20 mins, under load, and it was steady at 45-60 psi. He gave it a tune up instead and said they'd all it was. Wrong. That's why I hesitated to go back to him and am trying to figure it out myself. Can't remember what the tank level was at when he tested it.

[ranger098]

Did you get this figured out? It all sounds similar to an issue i had with my mastercraft. Water in the gas. Water will sit in the bottom of the tank and the fuel will sit on top. when you get lower on fuel level the engine will burn more water and less gas and give you problems. Also, i am pretty sure your boat doesnt have a "computer" since its carbed. You certainly dont have an ECU, but maybe theres some other computer i dont know about. Not to rub it in, but i sold the MC and now have an awesome 2002 mobius LSV carbed that i absolutely love. Runs perfect.

Pull up the floor (or there may be an access hole in your floor that you can open up), syphon a bunch of the gas from the tank into a clear bottle and see if there is seperation. this will tell you if theres water in the fuel. in my MC, sometime it would run perfect and then all the sudden just start to stumble and only idle, couldnt rev up (unless in neutral, then it would rev up fine). it would never die, just couldnt accelerate or get on plane. sometimes even on acceleration, it would be studdering and trying to rev up but couldnt, and there would be spurts of normal acceleration but return back to sputtering. this was the fuel pump grabbing water, then gas, then water.

Hope that helps... and please keep us updated on what you find.