boat automatically slowing down?

hey guys,
I just bought a 2000 supra launch direct drive. Its been running great but every now and then if I run it for a while it all of suddon throws itself into the iddling speed. I figured it was a problem of over heating and it has a sensor that would shut itself off if it was running hot. Checked the impellar and and water pump looked good and water was pumping fine to the thermostat housing (also put a new thermostat in last week). I also was noticing my engine is steming out of the exhuast and then looked and saw a slight leak behind the main pulley on the front of the engine.The person that owned it before me put in alot of extras and there is a bad ground/and or voltage issue so when run all gauges jump to the right, but as soon as u slow down the temp gause (as well as all of the other gauges) goes right back down to 165 degrees so im confused as all get out. I am fairly new at working on these boats and trying to learn as much as possible on how to fix things myself. Any input would be greatly appriciated!

OK...
1. Water behind the pulley. most likely coming out of weep hole, your boat being a 2000, it most likely needs a new water pump (recirculating pump).
http://www.skidim.com/prodinfo.asp?number=WP-2232MN
Even though it is cooling fine, the bearing may be shot allowing water to come through the seal. having just replaced the thermostat, I am assuming you already checked the housing and related hoses....
2. Gauges pulling to one side and kicking down to idle speed...bad ground. Check where the transmission bolts to the engine, drivers side, lower bolt. Should be two wires there bolted in. make sure both are clean and free of corrosion, replace the conectors if needed. Main ground from batteries will be front of engine passenger side, just to the right of the water pump. again, make sure it is clean and corrosion free. batteries are self explanatory. Also, there is a black rubber main plug right above the transmission bolted to the back of the block. pull this off and inspect all the pins, make sure there is no corrosion. Finally, inspect every sensor wire (appox 8) for wear and/or corrosion. IMO boat wiring is easier than car wiring as there is no common ground, but you know what they say about opinions....

hey man that part looks like exactly where its leaking. how hard are they to change out? and i will check into the ground wire's. The guy before me put in a custom hard ballast tank with two pumps four tower speakers, a sub and some other little things so I was thinking that the battery might not habe enough voltage, but my buddy who is weathered mechanic said its gotta be the ground.

Not that hard to change the water pump, 1.5 hours tops? make sure and order a new belt and gasket with it. you have to remove the raw water pump support bracket and swing it out (at least on mine you do) to replace the belt.

While you are at it check over the previous owners wiring and look at the quality. Sometimes stuff looks OK but has hidden shortcuts or no no's. Look for proper fuses and point or origins for new power lines.

While doing the water pump also install a new theromstat and impellar. This way the cooling system has been totally refurbished.

Hey guys checked the ground wiring and the two bolted on the back of the transmission block is completely gone. The connector is still there but no cable? Where would this ground be ran from so I search for this wire that has disappeared....

Run some jumper cables from the battery to the block and take it for a run on the lake. Then remove the cables and see what happens. You can never have too many ground straps on an engine. I have seen them on starters and alts too!!!

As for finding the wire in question. Follow the ground from the battery and go towards the engine.

Yea did go from the battery to the engine. no wires lose or dangling , but the guy who had the boat before me put so many extras for the streo ( he owns a stereo shop) the wiring is crazy. I am going to ride tomorrow if the jumper cables do solve the problem what kind of wire should I run? I am assuming I can just run one from the battery to place where the fitting is close to the transmission?

Like I said earlier I am such an newbie when it comes to this stuff, but I guess it's better to do this myself then to pay some crazy amount of money to have some one else do it...

Thank u guys for all the help!

what motor is in this thing? is it the "Monsoon" MPFI3?
could be also if you have a bad sensor, relay or actual physical condition other than a ground - the engine module will go into "Limp" mode all by itself and only allow so many rpms etc...only chiming in because the Legacy has that motor and I also have it in Chevrolet "Ramjet" form in a pickup... pretty familiar with that happening... but - I hope it's just a bad ground! LOL

I am in agreement with the limp home. MY fear is this....if the wire is there from the battery to the FRONT of the block, the ground strap missing off the back of the block is going to the ECM. he had tohave relocated it somewhere, or the thing would never start. suspect he ran it to a place that has abd contact. Some no-no's: intake manifold. this is 99% isolated by the gaskets, slightest bit of rust on the intake manifold bolt and you lose ground. Head bolts are a no-no. pretty much anywhere on the block except the engine to transmission bolts is off limits. I bring up the intake manifold because I have seen that one on an IO i bought in 1997. If it's a 2000 Launch direct drive, should have the indmar assault in there, is it carbed or TBI? I think both options were available that year....

Thought the engine was more basic than what it actually is... In that case please give us a little more info on the engine size brand and fuel delivery type...

With a more computer operated engine grounds are important but more than likely it is a sensor/computer glitch.

Is there a way to check for codes???

Yea there wires everywhere! Haha but today I went out and the boat was automatically shutting down " limp mode" about every 1/2 mile we would sit for about a minute then she would take back off so me and buddies started looking at the engine and block we saw a wire going into a metal plug towards the top front right side into the motor. We unplugged it and she ran fine.. With the plug not connected the boat didn't want to start, but once we plugged it back in it would start up. we monitored the temp gauge and it never got over 170 while running. We wake boarded for a couple hours and all was well... I'm thinking it might be a bad sensor.... If indeed that was the sensor we pulled out.

My motor is an indmar assault PCM... I think is a 350 chevy or 351 ford ( again I'm a big amateur) and it's electric fuel injected... Hope this helps

Ok so were do you get that it is an Indmar Assault PCM? because Indmar and PCM are two different motors. It is a 350 Indmar btw. PCM motors were not available by supra in 2000. Take it to your local Supra dealer, they can hook it up to a computer and tell you exactly what is going on. There is no point in guessing what it is and randomly pulling connections when you dont know what your doing and it is so easy to get help.

Thanks... but once again I'm 26 never been much on engines and I'm trying to learn as I go... There is a problem though the closest dealer is about 3hrs away... Can it be hooked up to any computer or does it have to be a specific type?

LOL...welcome to the boating world.
The computer on a boat uses MEFI, does not work with OBD (automotive) type scanners. kills me, as I own 2 VERY good scanners and can't use them on the boat. 3 hours away? may want to try fixing the easy stuff first. Again, check for corrosion and grounding problems. If your water temp sensor is working at all, you can write that one off. top right side sounds like MAP sensor...can you take a picture? this IS an automotive sensor, shoud cost about 30 dollars, which is a lot cheaper than 3 hours of hauling. for your engine, 1998 camaro 5.7 parts should fit. always take the part with you to the automotive store because electronic sensors are not returnable. The fact that unplugging it and plugging it back in allows it to run the rest of the day really sounds to me like a corrosion problem. Get some contact cleaner and dielectric grease, clean EVERY sensor connector, again looking for corrosion and bad connections. make sure the previous owner grounded the stereo system straight to the battery and not to the engine block. Same with the power wires, should not be tied to starter (this would be more difficult but I ahve seen crazier). those 2 ground wires that are supposed to be on the bolt connecting the transmission to the engine really need to be there, you ahve the same engine as me, I'll look tommorrow to see where the other end is.

1998 camaro is an LS1 it is not like the motor in your boat at all. i repeat NOT AT ALL! your is either an LT1 or vortec based GM motor. again 3 hours is a long way but how many hours have you waseted so far? Do it right do it once.

no, it's not the same motor, you are right. Mine is a 2002, indmar assault (350), same as his, and 1998 Camaro 5.7 is exactly the same as far as cap, rotor, map sensor, tps, iac, etc. makes it much easier to get parts when you give them 1998 Camaro!

Check not only the MAP sensor but also there should be 3 relays that govern the ECM. sometimes it's as easy as swapping a relay out. If the ECM detects anything improper - low oil press, temp etc... it'll go into limp. If none of those conditions exist it's usually a bad relay giving the ECM bad info. 20 bucks - 30 seconds to swap. Check the relays first - then move downstream to sensors ( cheapest to costliest) and you should be able to bird dog it fairly easily.

http://sdparts.com/details/gm-perfor...parts/12499120

If this is your motor - you can get a code reader and book from Scoggins Dickey also - it's a blink type reader. - This engine was developed by GM and Indmar in the mid 90's then around 03' GM started selling it as a crate engine. The old Legacy I owned had it - and I bought one in 09' for a little pickup I own. I think Indmar only offered it as a powerplant for a couple of years. Had the same issues with the one in the truck as you are describing. Relay fixed it! - but I have an advantage possessing the code reader and the Ramjet tech manual.

i'm not sure what auto parts store you go to but the 98-02 camaro is an LS1 (347 cubic in) it did not have a cap and rotor or a distributor for that matter the LS1 has 8 indiviual coils. look it up. A v8 camaro has'nt had a distributor since 1992. 1993-97 had optispark a different animal all together
http://i701.photobucket.com/albums/w...tore/005-1.jpg
this is my 99 camaros LS1 nothing like the Indmar assault 325 that is based of the 96-03Vortec headed chevy motor.

LOL...I see where the confusion is now.

What I did was took the part number off the sensor directly....

GMRLS1IAC

Which I found here....

http://www.nookandtranny.com/mm5/mer...y_Code=SENSORS

I know it's not an LS1, but for my engine a lot of the sensors trade straight over. The IAC, the MAP, the knock sensor, etc. When trying to amtch them up at the time, I just found it easier to ask for 98 camaro....

I used the IAC part number because that ended up being the part that fixed it... I had never seen one go bad, but talk about an expensive trouble! burned 3/4 tank of gas getting to the launch ramp...(about 6 miles)

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Originally Posted by jsmilez

hey guys,
I just bought a 2000 supra launch direct drive. Its been running great but every now and then if I run it for a while it all of suddon throws itself into the iddling speed. I figured it was a problem of over heating and it has a sensor that would shut itself off if it was running hot. Checked the impellar and and water pump looked good and water was pumping fine to the thermostat housing (also put a new thermostat in last week). I also was noticing my engine is steming out of the exhuast and then looked and saw a slight leak behind the main pulley on the front of the engine.The person that owned it before me put in alot of extras and there is a bad ground/and or voltage issue so when run all gauges jump to the right, but as soon as u slow down the temp gause (as well as all of the other gauges) goes right back down to 165 degrees so im confused as all get out. I am fairly new at working on these boats and trying to learn as much as possible on how to fix things myself. Any input would be greatly appriciated!

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Check your MAP sensor