First trip out in my 89 Comp

[tazman7]

I took the boat that I just bought out for the first time this weekend to just run in around the lake to kinda get the feel for the new boat I just got a couple of weekends ago.

When I test drove it, it got hot (200 degrees) and the guy said that the thermostat was stuck, so I got a 143 degree thermostat for it which I was told to get by some people on wakeboarder.com

So I filled it up with fuel and a bottle of seafoam on my way to the lake to help clean out the carb...(I put this stuff in everything i own, it works great)

I back it in the water and it doesnt want to start. So I crank and crank and crank on it..pump the throttle a couple of times and still nothing...by this time i am getting a little pissed/worried that I might have got a lemon... so i let it sit about 5 minutes and try again, still nothing. I find some starting fluid in the boat and give it a shot of that (even though I hate using starting fluid, we were an hour and a half away at our cottage and wasnt about to drive home without driving my boat) So it finally started. So I let it warm up at the launch for about 5 minutes and take off.. it climbs from 140 degrees up to about 185 so i back off of it and turn around and start heading for the launch..well it cooled back down to 145ish so i just putted around for a few minutes and lifted the engine cover and felt the engine and it wasnt to hot. (dont know what this told me but only thing i could think of)

So i took back off again and the same thing, so i just started cruising at about 25 and it stayed at about 160 then. So then i just drove around for about an hour and it seemed to start running pretty good. So I turned it off and let it sit then restarted it and it started fine...

Last season the guy that i bought it from put in the electronic ignition and did a complete tuneup. i pulled the spark plugs and they were like brand new... im sure it wouldnt hurt to put new ones in again but they seriously look like they were just put in..


Do you think the heating problem could mean it needs a new impeller/ He just put a new impeller in it the same time he did the ignition..

[wotan2525]

I'm certainly no expert, but 200 degrees shouldn't be warm enough to cause any damages or problems. Is your gauge only 200 degrees and you're worried that it is hotter than that?

I'm guessing either your impeller is shot or the gauge is simply not accurate. Impellers are very easy to replace and inexpensive.... if you'd rather troubleshoot it though, One way to test this is to completely remove your theromostat and try running it that way. I did this a couple of years ago and have never bothered to put a thermostat back in. If I had a heater this would be a problem.... but as it is the engine never gets warm and the only (possible) downside is slightly reduced fuel economy.

the upside is that if I notice my temperature gauge move at all it either means the irrigation valve is closed or the impeller has gone bad.

[Salty87]

you could have old impeller pieces restricting waterflow. you need to remove the impeller housing to check...i'd check the impeller anyway on a new to me boat. any chance it was run in saltwater...might want to check the risers/exhaust manifolds.

the temp gauge could be incorrect too, bring a handheld IR thermometer if you can. your hand works though, carefully tough the top of the riser, you should be able to leave your hand there for 4-5 seconds. it shouldn't be too hot to touch.

200 is close to boiling, not good for exhaust hoses or engines.

these are all things you want to know about your boat anyway...check for soft hoses and worn belts while you're in there.

[tazman7]

Does anybody have a picture of how to change the impeller or instructions, I have heard this is an easy job, I have just never done it.

thanks.

[OUI]

Changing the empeller is simple. Loosen the four bolts that hold the pulley. Then loosen the belt on the pulley by loosening the two bolts that hold it in place on the motor bracket. Remove the four bolts on the pulley and remove the pulley. Then there are two bolts that hold the water pump on to the bracket remove those and the hoses and you've removed the pump. Take the two bolts off of the pump face pull off the face plate and there's your empeller. You can inspect the embeller without removing it, if you need to replace the old one you may need a needle nose pliers to pull out the old empeller. The last empeller that I put in was a little tight on the keyway so I took a small file and opened up the keyway on the empeller a hair.

[tazman7]

So what I am getting from what you just said is that the impeller is in the water pump?

[Salty87]

So what I am getting from what you just said is that the impeller is in the water pump?

yep, should look similar to this...
http://skidim.com/images/RA057009.jpg

[rludtke]

I'm certainly no expert, but 200 degrees shouldn't be warm enough to cause any damages or problems. Is your gauge only 200 degrees and you're worried that it is hotter than that?

I'm guessing either your impeller is shot or the gauge is simply not accurate. Impellers are very easy to replace and inexpensive.... if you'd rather troubleshoot it though, One way to test this is to completely remove your theromostat and try running it that way. I did this a couple of years ago and have never bothered to put a thermostat back in. If I had a heater this would be a problem.... but as it is the engine never gets warm and the only (possible) downside is slightly reduced fuel economy.

the upside is that if I notice my temperature gauge move at all it either means the irrigation valve is closed or the impeller has gone bad.
wotan2525 is right, 200 degrees is not to hot, but it is getting near the top of the band. I would suggest that 150 is a little to cold for hard accelerations. The problem is with an engine that is to cold, is that it is not yet to the ideal dimensions, the dimensions the engineers intended it to be. Parts may be fitting either to tight, or too loose depending. Also, the engine oil will be to viscous if it isn't at the correct temperature. The correct operatoing temperature is probably between 160 and 220 degrees F. Someone mention that this is near boiling, and that is true at sea level atmosphere of 14 psi, but the boiling temp increases with pressure, and the engine uses a pressure cooling system. So the boiling point of the coolant is somewhat higher.

I guess my point is that damage can be done to the powerplant when operated either below or above the intended operating temperatures.

If the engine overtemps with the correct thermostat installed, then I would suggest the system is obstructd somewhere. The impellor outlet is a highly likely location as someone already commented.

[DKJBama92Mariah]

NO NO NO!!! 200 degrees is way too hot for a raw water cooled motor!

If it is 200 degrees at the thermostat housing on the intake manifold, that means its 225-250 in the cylinder jackets and in the heads. At that point you are getting steam pockets. The problem with steam pockets is they steam insulates the metal from the water causing it to get even hotter.

Auto and marine freshwater cooling systems operate at 6-12 psi with ethylene glycol mixed with water as coolant. Between the pressure and the antifreeze, this can raise the boiling point to 270 or so.

Engines do run more efficiently at 200 or so degrees, that is why FWC boats and cars have 195 degree thermostats, because the efi can be more efficient at that temp. With a RWC boat, you lose the benefits of the antifreeze and the pressure and you just can't run the motor that hot all the time. The hot spots caused by the steam pockets can melt all sorts of stuff and cause predetonation which can, if unnoticed, burn holes through pistons.

Early PCM RWC engines came with a 143 degree thermostat, and later ones a 160. PCM now states that a 160 thermostat may be used in all RWC engines in place of the 143.

Go ahead and take the raw water pump apart and inspect the impeller. Also check the transmission cooler for obstructions. My boat was brought to its knees by a single leaf in the transmission cooler that blocked probably 80% of the holes.

If these check out then you are looking for either impeller pieces in the block or clogged manifolds and risers. I'd go ahead and order a new impeller and a set of riser gaskets. Even if you dont need the impeller, it's good to have a spare anyway. The riser gaskets are for if you need to pull the risers to inspect the manifolds for corrosion/clogging; they're cheap anyway.

BUT WAIT! before you do any of this, check the connections to the sender (just aft of the thermostat housing. Also check the connections to the gauge, especially the ground and signal wire. The little nuts that hold the ring terminal on the post can work their way loose. A nutdriver of the right size is the perect tool for this job. I myself chased a "phantom" overheat for a coupla years that turned out to be poor grounding of the gauge panel altogether. My +12v and ground wires to the gauges were daisy-chained from one gauge to the next with short jumper wires and (non-marine ring terminals. After couple of years, these ring terminals get corroded and loose. This causes excess resistance and voltage drop near the end of the chain. Classic symptoms of this are high temp readings, abnormally high oil pressures, low voltmeter, and sometimes intermittent tach operation.

To check this you can always buy a cheap gauge kit from a parts store or maybe an online place like egauges.com (never used them myself, not endorsing them, never heard anything bad though.) Replace your sender with the one from the kit. Then rig the new gauge with a set of three long wires with alligator clips on the ends. The pos can got to the hot side of the starter solenoid, the neg to a good ground on the block, and the other wire to the post on the sender. Easy, portable temp gauge tool. They may also make a mechanical gauge that just screws into the hole, i'm just not sure on that one. .

EDIT: You can also check just by tightening the nuts on the back of the gauges. That doesn't cost anything. I'm just biased in favor of cool homemade tools.

sorry for the long ramble. Any thoughts?

[Boiler with a Supra]

Been through this a couple times with my 89'. For sure it is the impeller. It is either stiff, lost some fins, or just shot. The reason it is running ok at medium speed is just that you are pushing water just by the action of the boat. This is a 15 minute fix as previously described. I carry an extra because it happened to me once on a holiday weekend when the marinas were closed and you are really dead in the water. I have also heard that deterioration ofter happens from people running the motor out of the water for a bit. The water really helps with keeping the impeller lubricated and soft.

[DKJBama92Mariah]

For sure it is the impeller.

What makes you so sure? It could be many things. Blanket statements like that based on less than perfect information can cause more harm than good and certainly can waste money.

Diagnose first, repair second.

[Boiler with a Supra]

I will defer to his response upon change.

But in the interim, the "harm" I am suggesting costs $10 and 15 minutes to do for identical symptoms to my experiences. Additionally if you have a 19 year old boat that you just bought, this change is simply preventative at a minimum. If I was asking him to go buy gauges and electrical diagnosis that may not be useful going forward, I would have a different approach. If you have a headache you don't do an MRI before trying aspirin. I am not looking to get in a pissing match and I do not use "for sure" lightly in any motor diagnosis. I am not a certified mechanic or trained professional, just a guy whose had the same frustrating experience. Call it for what its worth.

And now we wait to what the issue is.

[riveredge]

Agreed that we don't want to jump to conclusions; checking the impeller is a good place to start... blockage somewhere else is a possibility too. I had my gt-40 run up to 190 ish at idle for a whole day earlier this year, then if I went faster it cooled back to 150-160; idle again and back to 190 after a few minutes. It was a hot day but it did it at night too. Then all of a sudden, all fixed. I didn't touch a thing. Simply blockage somewhere, I presume. The boat had a new impeller about 30 hours prior to that incident, otherwise I would have pointed to that. Would have been first on my list to check since the strainer looked clean... Anyway yeah lets wait and see what the OP says next!

[DKJBama92Mariah]

Yeah, OP's feedback would be excellent here. After I posted last night i realized the original post was back in May. I sure hope he's got it fixed by now.

Boiler,
No hard feelings man and welcome to the forum. Confirming that he is actually overheating should be done before he takes anything apart. Yes of course he should check the impeller, we are all in agreement on that. An IR thermometer would be perfect here as well so he could pinpoint what parts of the motor are getting hot if at all.

I am aware that a bad impeller will cause it to run hot at idle and cool off at speed because of the ram effect on the water pickup; I have experienced this before in my boat. However, if you read his post carefully you will see that he is overheating at speed, not at idle. An IR thermometer would be perfect here.

However, if you want to criticize my diagnostic procedures, then why not take the time post some procedures of your own rather than blanket conclusory statements.