AQ 131 Overheating

"Hello,

I just took my proj

"Hello,

I just took my project boat out on the lake for the first time. It is an AQ 131 with fresh water cooling. When running it on muffs, it ran at about 175 degrees, but out on the lake it was at about 200, maybe even as high as 210 degrees, a little too warm for my liking. It has a new thermostat, impeller, anti-freeze is full, raw water intake fitting on the outdrive has been replaced. Can the exhaust manifold be causing my problem? How can I tell if it is plugged? I did notice that the manifold was warmer than when I ran it on muffs, and a little warmer by #4 cylinder compared to the other three. I know it is a raw water flow problem, just wondering if the manifold is causing the problem.

Thanx for your help.

Rob."

"Rob: if the manifold is old,

"Rob: if the manifold is old, it could be choked with mud and scale. One way of checking is to remove the copper pipe under it and stick a screwdriver: if it comes out muddy,t hat's a bad sign. Also, you can slide downwards the rubber hose connecting the exhaust manifold to the exhaust pipe, then check the water pasages in the exhaust manifold (they surround the gas outlet. If the are choked, you can take the exhaust manifold to a radiator shop to boil it, but you are probably better off replacing it for a new one. When they reach the stage that they clog, there is usually little good material (cast iron) left in the walls, and if you boil it chances are that it will become eventually perforated without giving warning.

Also, have you checked if the strainer by the heat exchanger is clean?

In any case, the temperaure range for your engine coolant is 180º- 198ºF."

"Thanx El Pescador for all you

"Thanx El Pescador for all your help on this and some of my other posts. We are in Kelowna on holidays and found that she was running a little warm. I have not looked into the passages of the manifold, would have to pull the boot and possibly the manifold to do so. The boat is a 1992, do you think that the manifold is ready for replacement regardless? I guess why I am stumped is because it ran cool on the muffs but not out on the lake. Will be replacing the raw water pump, it was new but maybe it got damaged when we were trying to start it and did not have sufficient water flow. The strainer is clean, when the engine is running, should that container that houses the strainer be full of water? If it is not full, then that suggests a raw water flow problem. However if it is full, then maybe the exhaust manifold is plugged. That strainer is downstream of the raw water pump and a full container suggests that the passages in the manifold are plugged restricting the water flow. Does that make sense? Your response is greatly appreciated.

Have a great day,

Rob."

"I doubt that the pump is at f

"I doubt that the pump is at fault. That is, not unless you sucked a load of sand into it. However, you say the strainer looks good, so...

The '92 manifold is likely a problem but I don't have experience with fresh water boating. In salt water, those things might last 3 seasons if lucky. My OHC four bangers have bronze manifolds which were available back in the 80's for $550 apiece. In any case, check it per Pescador. The strainer is downstream of the pump? On my engines the stainer is upstream and are always full when hot and gradually drain down."

"Thanx Dennis for your input.

"Thanx Dennis for your input. Hopefully El Pescador will be able to give me some more advice. Replaced the raw water pump, ordered a new cap for the heat exchanger. Water was too rough today to try it out, but will do so tomorrrow. If I am still having problems will need to bite the bullet and order a new exhaust manifold.

Thanx again for all your help and advice.

Have a great day,

Rob."

Kelowna? It wasn't one of

Kelowna? It wasn't one of those 100+ degree days when you were testing it was it? If it was imagine what the temps were inside the doghouse. Also you didn't say if you were on plane when the temps got hot or at idle. If it gets hot on plane only then check the hose connector as well. It's cheap and is a problem point for over heating issues when it starts corroding away. El Pesc has mentioned this numerous times.

"Thanx for your input PugetSou

"Thanx for your input PugetSounder. The hose connector on the leg is new, I replaced it about a month ago. I also installed a new raw water impeller this morning and it did not make any difference. Yes it is about 90 degrees out here. It may get a little hotter on plan than at slower speeds, but not by much. I pulled the exhaust manifold thinking that was my problem. The passages seem clear, put a garden hose to the raw water inlet on the manifold and got great flow out the other end. I am quite sure that the exhaust manifold is not the problem. Have ordered new gaskets and will be re-installing the old one back. Seems like it is in great shape, all the passages are open. Does anyone know the torque specs for the manifold bolts? My Seloc manual does not contain such information. Great manual.....NOT.

More suggestions are always appreciated.

Thanx and have a great day,

Rob."

"Rob, regarding the exhaust ma

"Rob, regarding the exhaust manifold bolts torque, check this:

http://www.marineengine.com/discus/messages/12487/32909.shtml

Maybe is time to check with an infrared thermometer the coolant temperature just to verify that you are not chasing a ghost? "

"Thanx El Pescador for the lin

"Thanx El Pescador for the link. 12 to 14 ft lbs sounds about right. You are correct about the infrared thermometer, however I do not have one here, but do have access to one in Vancouver. Even if the gauge or sending unit was faulty, the fact that the temp was OK on muffs, and then increased when out on the lake has me somewhat concerned. I am not sure that this is a problem that I can fix out here, even though I have tried. May have to wait, but even if it is running a little hot, as long as the coolant does not boil to me suggests that I am still safe, even though it is warmer than I would like it to be. My guess is that it is around 200 degrees F, and I think I should be OK for now. Any comments?

Thanx again for all your help. Have a great day,

Rob."

"When you are running the engi

"When you are running the engine with muffs the engine has no load, so the temperature cannot go too high; I would say about 180º, which is the temperature at which the thermostat starts opening. Again, the temperature range of the thermostat is 180º-198ºF. As long as the coolant does not boil and the temperature does not deviate dramatically from 198º, I think you will be fine.

BTW, have you checked that the alternator belt is not loose? It happened to me a few years ago on an AQ140 and the first indication was high coolant temperature. It probably won't be your case, but it won't hurt checkig; that is.... as long as you don't try to check the belt tension by touching it while the engine is running. Believe me or not, I saw a guy a few years ago loosing part of his fingertip for doing that (and no, that dumbass wasn't me )."

"Thanx El Pescador,

May nee

"Thanx El Pescador,

May need to start referring to you as Professor El Pescador, for the wealth of knowledge you share with rookies like myself. I will check the alternator belt, I know it is a little on the loose side, but not to the point where it is squealing. I will just run it as it is for now and when I have time or even during winter work on it to try and get the temperature down. There is a bit of a learning curve from working on cars to boats. Learning lots, unfortunately sometimes the hard way. Regarding dumbass, I have a nice little gash on my leg that I got when it touched the alternator fan. Oh well, $&#* happens. Time to enjoy the rest of my holidays.

Thanx again for all your help. Owe you a few beers.

Have a great day,

Rob."

Ok here might be dumbass quest

Ok here might be dumbass question...If the alternator belt is lose how does that affect overheating???

water circulation pump runs on

water circulation pump runs on the alternator belt.