boat automatically slowing down?

[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!

[Seabeejamie]

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 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....

[jsmilez]

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.

[Seabeejamie]

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.

[DAFF]

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.

[jsmilez]

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....

[DAFF]

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.

[jsmilez]

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!

[Tim405]

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

[Seabeejamie]

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....