View Full Version : 1987 Comp idle speed/almost overheat
05-10-2004, 03:10 PM
Took mom out for mother's day yesterday. She brought her 'new' 87 comp home from AZ Saturday, so we needed to get it out on Lake Mead to see how she ran.
The first issue we had:
was no-wake idling. When I click the throttle just past neutral and into gear, I expected to have a slow, no-wake idle. I did not, and had to click it in and out of neutral in order to stay slow enough for in-harbor cruising, but no propwash=no control, so it was a frustrating cruise to open water.
The engine idles at 1100rpm in neutral, then drops to around 800 in the just-in-gear position. I am guessing that this is too fast, but I ain't sure. I don't think it's normal, though, to not be able to motor out under low power without clicking it in and out, in and out.
Gets hot when running at cruise, about 250, (just enough to beep a warning) then drops suddenly to around 165-180 then steadily climbs back to 250. There was no heat issue when motoring around the docks. I am guessing thermostat, due to the climb-and-drop, climb-and drop, but someone else may know better... The fact that it only gets hot when running higher rpms (mind-blowing to a car guy...where the hell is the radiator, anyway?? :p ) makes me think that there could be issues with the water circulation. There was water in the filter canister, though, and after trailering, a good half gallon or so emptied when I ran the bilge pump. If anyone has suggestions, I am looking for them.. Thanks!!
05-10-2004, 09:34 PM
replace the water pump impeller, the impeller probaply has a set to it and is not able to pump enough at high speed to keep the engine cool. dont waste your time with the thermostat unless you are in salt or brackish water. don take the thermostat out because this will affect your warm up temperature and ultimately affect your idle speed. out of gear idle on your motor should be around 750 rpms. if you are carberated (sp?) you can adjust this with the idle screw by the throttle cable on the carb. dont mess with the idle mixture screw it will throw you for a loop. any questions call me 540-895-9616 rob
05-11-2004, 12:04 PM
the thermostat is cheap and easy to replace. you could also test it in hot water but that's pain in the butt. you can't touch the sides of the pot, etc.
with it going from hot to cold like that, i would guess that the impeller is ok because the engine does cool down. it just needs the thermostat to cooperate. changing the impeller in a new-to-you boat is a good idea though. might as well get 2 so you have a spare.
can you explain the water in the filter canister comment? what canister?
as for the gallon in the hull, your packing gland on the drive shaft could be leaking too much or might need to be replaced. did you ever notice the water pump on the front of the engine weaping? it'll go out the same as an automotive pump. swimmers will also bring a lot of water in the boat when they get back in. there are other possible sources for leaks but i'd start with these.
flyinj is correct about the idle, i aim for 700 rpm at idle. that will drop a bit when you put it in gear.
have you checked the boat over fairly well? i'd be nervous about hitting such a big lake with a new/old boat. replace any worn belts or hoses, impeller, change oil, tune-up, new batterie(s) if they aren't in good shape.
get to know these people: www.skidim.com
they can get all of the parts you'll need at great prices. plus, their service manager used to own a comp...vince. he knows his way around older supras very well.
05-11-2004, 02:38 PM
Thanks very much for the help!
The canister I referred to is in the engine compartment between the fresh water inlet and the engine, at the rear. It looks like a giant clear fuel filter, about quart size. I assume it is just that, a filter of some kind for the fresh water.
As far as pumping the bilge after we trailered, I don't think it was an unusally large amount of water. I seem to remember our '74 nautique (yeah, I know...) pumping out about the same amount. The comp has an auto bilge which I thought was pretty cool, and I had that on the whole time, rather than run the pump on manual. It never switched on, so I figured I ought to run the manual one after we were dry.
As far as running this new old beauty on Lake Mead, I really have no choice. But there are rangers in full force, so if something dire did come up, we would be all right. Someone is getting towed in every time I'm at the marina. I grew up on this lake, and it can be a beast, rivaling the great lakes for sudden storms and high wind. Most people don't know it, but Vegas is the third windiest city in the U.S. (or some such statistic) I've been getting lazy, though, driving a pontoon for the last few years. It's like driving a 'vette after getting used to driving a bus.
Well, since the boat is legally my mothers, (that's what she thinks...hehe) and her being the thorough type, she is having everything once-overed by a shop where she has a good relationship with the staff. They are doing belts, hoses, and I assume the impeller and related parts. None of them need it, however. The engine is gorgeous and clean, the transom is like concrete, and there isn't a trace of cleaned-off oil anywhere. The belts are black and slick, probably replaced before the seller put it on the market. Hoses still have label stickers on them.
I will definitely adjust that idle down. I figured that was the issue, but I'll let mom get it serviced first, and then see if they did it. I won't make any carb adjustments, just the idle. The boat starts like a fuel injected nissan.
I have no trust in shop guys. Not to mention it's my arse that will be swimming, not theirs.
As far as the cooling goes, I wasn't planning on taking the thermostat out completely, nor testing it, just popping in a new one, probably a 180 or 190. I have checked out skidim, and will probably get an impeller or two. Where is it located? I assume it's not the same one from the water pump that would be on an automotive engine. Sounds like it's easy to replace. -sigh- If only these things had chevy's instead of fords...
Thanks very much again for all the help. I will keep everyone posted.
05-17-2004, 01:18 PM
Opened the pump and boy, was it a mess. The impeller was shredded in several places, and the pieces were clogging the ports. Have two impellers on order, and the boat shop guy replaced the bearing in the pump and trued the pulley for me. I WILL get that boat on the water soon.
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