88 120 looper overheating at idle

[MAC56]

Ok.. this is my first post, so bear with me...<br /><br />I have a 1988 17' Wellcraft with a '88 120 Johnson V4 looper motor. I bought both used and have been bringing both the hull and engine up to good running order. I have had it in the water a few times and have had several issues, but the most perplexing is that the engine overheats at low speed or idle. The warning horn sounds and stays on until the temperature drops. I am running pre-mixed fuel since the VRO was disconnected. <br /><br />I replaced the water pump witha Sierra kit that DID NOT include a new housing, just the impeller, plate, gaskets, but NO bushing, housing or housing liner.<br /><br />After replacing the water pump the engine still overheated. I replaced the tstats. No change. The "Pee" stream is not a forcefull stream like some I have seen on other motors such as a Mercury, so I am not sure what to expect. But the motor temperature is normal at any speed above about 2500 RPM.<br /><br />What should I do next???

 

[waterinthefuel]

Re: 88 120 looper overheating at idle

Welcome to the forum!<br /><br />As for your problem, could it be a faulty horn? Do you know for sure that it really is overheating? It could be something stopped up somewhere in the water's path to your head.<br /><br />Those are my two cents.<br /><br />Now, wait a few hours for someone who knows what he's talking about! LOL

 

[OBJ]

Re: 88 120 looper overheating at idle

As waterinthefuel suggested, you need to verify that it is overheating.<br /><br />Does the horn come on as soon as you start the engine? <br /><br />Look for the two flat places on top of the block just forward of the heads. Let the engine idle for a while and then put your fingers on the flat places. You should be able to lay your fingers on these flat places for several seconds before having to remove them. If you can't, the engine is getting hot. You will know.<br /><br />It is possible for one head to over heat and the other not since both heads have there own t-stat. When your replaced the t-stats, did you get the newest t-stats? These are one piece t-stats that replaced the originals.<br /><br />If the engine runs normal above 2500rpm suggest pluggage in the water passages. If this is a salt water engine, you could have salt build up in the narrow passages in the heads restricting flow at low speeds. You could try to remove the salt build up. A product called "Salt Away" may help. <br /><br />You could also have a bad heat sensor. IF, the heads appear normal at idle, disconnect each sensor one at a time to see if the horn stops. Each head will have a single wire coming from it. This is the sensor lead. Just pull the boot back and disconnect the knife connector.<br /><br />One more IF......if the heads are running normal at idle, disconnect both sensor leads. If the horn stays on, the horn module is probably bad. <br /><br />Keep us posted as to what you find.....thanks!

 

[ezeke]

Re: 88 120 looper overheating at idle

I still have that thermostat control system on my 140hp 1988 looper and I have a gauge that always has indicated that the motor is hotter at idle than when running. The gasket under the thermostat cover has a little opening in it that you have to be careful to keep clear.<br /><br />A lot of people did away with that system and replaced the thermostat control with the ones used in 92 up.<br /><br />I bought the stuff to do that but never have gotten around to it.

 

[OBJ]

Re: 88 120 looper overheating at idle

Stay away from the oil threads and you might get it done ezeke......... <br /><br />Popping pop corn for so many takes a while.

 

[MAC56]

Re: 88 120 looper overheating at idle

Thanks for the welcome and ideas.<br /><br />No, the horn does not come on until after the engine has been running for 20 - 30 minutes or so to arm up.<br /><br />The thermostats that I bought, looked identical to the originals, in other words you can take them apart just like the old ones.<br /><br />When I replaced the tstats I did not replace the rubber diaphram-gasket since it looked in good condition. I also looked into the the head through the tstat port, and although I know the boat has been used in saltwater I was told that most of its life its been used mostly in freshwater. The water jacket looked pretty clean, but obviously I hhave NOT removed the heads to look everywhere.<br /><br />When I ran the engine in my driveway yesterday, the temp gauge went into the red just before the warning horn went off. So I think the temp sensors are doing their job. Both cylinder banks were too hot to touch.<br /><br />How forceful of a stream should I be getting from the indicator? I was told that without knowing what it was like when new, its hard to know exactly what it should look like.<br /><br />My thinking is... maybe to drop the lower unit and get a complete water pump kit??? or maybe even remove the linkgage to the manual high speed water valve??? (or whatever its called).<br /><br />I will look for Salt-away.. since that sounds like a possibility as well .. I will check out the sensors today after work and see if its one side or the other.

 

[katbird]

Re: 88 120 looper overheating at idle

I would also like to know how much force the water stream is suppose to have on these 80s motors. mine runs like a garden hose turned down low with no force at all. my mercury has a strong stream of water.

 

[ezeke]

Re: 88 120 looper overheating at idle

I did not mean to understate the importance of the vent hole being clear on the gasket under the Thermostat cover. It and the vent are crucial. Sometimes folks use gasket sealer and it gets in the hole - that will not work.<br /><br />Also, to be sure, I checked again with the J/E dealer and was told again that the Thermostats were updated and should be the black sealed ones.<br /><br />To Ron Regan, <br /><br />The pressure is not indicated by the diameter of the opening on the tell-tale, which on the loopers is quite large.<br /><br />Here is a link that will give you a better idea.<br />Water pressure table<br /><br />Scroll to the table at the bottom of the page and you will see that most outboards are within a similar range.

 

[MAC56]

Re: 88 120 looper overheating at idle

Well...<br /><br />Came home tonight.. ran the engine on the hose in my driveway.. for at least 30 minutes and it never got hot to set off the warning horn... I guess I will have to wait until I get the boat in to the water this weekend to really see if I have a problem.. I will let you know!<br /><br />next questioon is related to the VRO .. it had ben disconnected for a long time.. so I will read through the archives and see how I can check to see if the VRO system actually is working so I can avoid messing with the pre-mix.....<br /><br />Mark

 

[MAC56]

Re: 88 120 looper overheating at idle

Ok.. here is my update from last weekend...<br /><br />Took the boat out on the lake.. engine started ran beautifully.. (I removed and cleaned out the carbs last week as well).. I idled through the no wake zone after warming the engine up at the dock for 5 minutes or so.. the engine temperature did rise and got close to the red but did not set off the warning horn.<br /><br />I drove around for the next two hours or so at all speeds from idle to WOT everything ran great.<br /><br />Had lunch at a boat-up restaraunt .. and again when trolling the temp went up but no warning buzzer. At the end of my day when loading the boat on the trailer.. (after about a 20 minute low speed return to the dock) the high temp buzzer went off .. so my only conclusion at this point is, that there must be some restriction that is causing the engine to not get enough water when sitting stationary. At even a slow forward speed.. it never overheated. So, until I can get a infrared temperature gauge and read each cyliner bank and confirm which bank is the one setting off the overtemp .. I guess I can just keep moving forward!<br /><br />Also, I re-connected the VRO since it had been disconnected for quite some time. I have been running pre-mixed fuel at 50:1 WITH the oiler and had filled the oil tank full before heading out. It looks like the VRO pump works fine as well.

 

[MAC56]

Re: 88 120 looper overheating at idle

New problem.. guess I should start a new thread.. but anyway... <br /><br />When I have the power set to 2500 RPM .. the boat and engine runs great.. stays at that speed and will not vary all day long.. however.. if I throttle up to 3000 rpm the engine will sit at that speed for maybe 15 seconds or so.. and then gradually speed up! It will top out around 4000 to 4500 rpm unless I throttle back down. If I close the trottle lever until I get back down to 3000 rpm, it will slowly start dropping until it goes to 2400 to 2500 rpm. I can go WOT and the speed stays at around 5000 rpm.. I can even throttle back down to around 4000 and its fine.<br /><br />I did notice one thing, when I cleaned out the carbs two of the carborators had the correct 50 sized intermediate jets. The other two had 47 and 43 numberd jets. Could this be the problem? Any ideas of where to focus my attention?

 

[Tom Scully]

Re: 88 120 looper overheating at idle

WOT for that motor should be higher, around 6200 rpm.<br />I'm not positive about the jet sizes but I think they should all be the same. I don't think the different sizes are the cause of the surging. Sounds like there is some blockage in the carbs or a pump issue, since this happened after re-connecting the VRO/OMS try disconnecting it and see if the problem persists. Try pumping the fuel bulb and see if it has any affect on the surging.

 

[Dhadley]

Re: 88 120 looper overheating at idle

Lets "start" by completeing the water pump job. get the complete kit including the housing and liner. I'd use the later kit which is the high pressure kit.

 

[MAC56]

Re: 88 120 looper overheating at idle

Thanks for the ideas. The surging was tehre BEFORE I reconnected the VRO pump, so I don't think that is an issue. I have read about vacuum check valves??? Could this cause this kind of a problem. If it sounds like I am grabbing at straws I guess I am... I don't think the water pump is an issue.. since my temp gauge when running at any speed above idle is right in the middle of teh gauge.. BTW the prop is a 13" X 19" .. not sure if I should really get many more RPM's out of it.. the manual says it should be between 5000 - 5500 rpm .. when lightly loaded, I have seen speeds near 5500 rpm and 42 mph on the gps.

 

[perkdp]

Re: 88 120 looper overheating at idle

my 1 cent worth.... in driveway muffs on, water volume/pressure. <br /><br />on the lake high speed ... water volume/ pressure. <br /><br />pump leakage or blockage, if its impeller maybe the wings are folded wrong or one set folded toward each other closing one pump point / reducing volume/pressure.

 

[rottenray6402]

Re: 88 120 looper overheating at idle

This may sound silly but your RPM fluctuation isn't when the hull gets up on plane and the engine speeds up as the resistance in the water lessens is it? Reverse when it falls off plane slowing down?

 

[ezeke]

Re: 88 120 looper overheating at idle

With all due respect, MAC56, when Dhadley says it is an issue, it is.

 

[MAC56]

Re: 88 120 looper overheating at idle

Well.. I am planning on redoing the water pump.. and that was my plan about getting the entire kit including the housing.. so.. I will start with that and replace the two jets .. then we'll see what I have.. and no, the problem is not from being on and off plane.. Ithe boat gets on plane easily at just over 2200 rpm when its tilted up... thanks for the comments guys!

 

[Solittle]

Re: 88 120 looper overheating at idle

I'd replace the thermostats or at least check them while you are at it.

 

[MAC56]

Re: 88 120 looper overheating at idle

Already replaced the thermostats.. see above.