Cooling Problem
 

I have a 30' Scarab with twin 7.4 Bravos. When I went out this weekend, one motor is running at 150-155 degrees, the other is fine. I changed the thermostat, but no luck. The housing is the new stlye, cast iron, and is getting pretty nasty, but seems to be unobstructed. The engines use circulating pumps, could that be the problem? I can lay my hands on the risers, so I do not think that's the probelm, but would appreciate any advice. Thanks.

When was the last time you replaced the Impeller in the Raw Water Pump(s)?

Almost 3 years ago, but I have good water flow through the exhaust.

150-155 temp is fine .....thermostat is 145* ....what temp is the other motor?

Both motors have 140 degree thermostats, the other motor never goes above 140. The temp on the motor in question has been rising over the last year very slightly up to this 150-155 level. Manifolds and/or risers?

3 years ago? That's your problem. Impellers need to be replaced every year. More often if you are in a really dirty river or lake. :lolhit:

Replace the impeller--in both engines. There is probably a vein broke off on the one with higher temp that is restricting water flow just a little.

Thanks! You guys convinced me. Any tricks on rebuiling the pumps, or do I just need to replace the impellers.

Not sure where to get it online, but i got mine from a local guy. It comes as a kit with new bolts, impeller, gasket, and housing. The housings are plastic aand wear with the impeller! just make sure you twist the impeller in the right way. Good luck

doesnt matter on the rotation ..it will flop around if you get it wrong .....lube it up good ....

Thanks! I've seen the kit online. I'll pull the pumps, get the numbers and make sure I get the correct kit.

The impeller won't cause hot running when on plane. Water is forced though by the movement of the boat. What you are doing is looking at the impeller to see if pieces are missing and obstructing flow by blocking the cooler. If no peices are missing you have not found your problem, if you want to call 150f a problem.

Nice. Always lube it up!! But yea I guess i didnt need to fight all the veins in the right direction! I try anyway.

Got my kit today. Plan on installing it this weekend along with filters and oil! Almost time!

Lube it up with what? Special lubricant, or just engine oil?

I alway just use wheel bearing grease.

Got it, Thanks.

Dishsoap works fine if you're going to run it fairly recent after the rebuild (and is more environmentally friendly).

Any type of normal lube will work if you're going to let them sit around a while (lithium grease, wheel bearing grease, a small amount of motor oil, gear lube, etc.). You just want something that isn't going to dry out by the time you first fire them up with water in them (so no WD40 or anything like that).

I agree, lost a vein of the the impeller and it is stuck in the housing. Make sure to take the housing all the way out and check it for rubber debris. I use vasolene to lube mine up. They have the kits in the classified section that have a brass housing. Looked cool to me. I have had plastic housings go bad before. Good luck and happy boating.

Seriously? Rubber is made from oil. If you use any kind of oil product on the impeller when installing you run the risk of molecularly changing the rubber and degredation.

Dish soap or maybe KY if you have some in the garage. (:D)

Put a zip tie on the impeller and get all the veins leaned over in the right direction. Then insert the impeller into the housing 1/2 way and snap the zip tie. It works like a charm. There have been several how-to posts on this in the past.

I change the impeller every 2 seasons. Use a couple of zip ties and compess it. Install the impeller and cut the ties. Very easy for a do it yourself project.

Well. took the pump apart, looked perfect, installed the rebuild kit, NO JOY! Impeller was perfect, no debis in the pump. Any ideas?

are you starting to run lean on that motor. fuel issues.
circulating pump starting to fail or the belt loose or slipping that drives the pump
thermostat sticking partial or any blockage

just shooting in the dark.

Fueling spot on, this problem is just with one motor, it could be the circulating pump, as the temp has been creeping up. But thre is no leaking on the circulating pump, and everyone has told me they rarely fail. I'll check it anyway.
Happy Easter to all! Safe boating!

Have you verified the temps with a heat gun? Sending unit could be giving you a false reading.

I was running no thermostat for a year, just rebuilt the motor and the old man put one in, trying to make me nervous. I figured good 10 min warm up and then let the water flow. What are normal v8 operating temps i know my can runs around 220 when i open her up for a while

should be a 142* stat .....should run 140-155* ..... thats ideal ....if you have flow issues could be warmer ...m

could be a supply problem with the drive .....the TA can corrode and cause the hose to collapse restricting flow to the pump ......m

Well, I shot the manifolds and risers, and the port manifold is running 150-55, almost 40 degress hottter than the other side. Riser is fine, but I think I need to change the manifolds. Any observations?

I believe the recommended service life for cast iron manifolds in salt water is 5yrs max. You can service them a couple times by soaking in muratic acid and rodding them out. Yours are likely getting clogged up with rust scale and restricting flow of seawater.

I was thinking that, I'll remove it this weekend, and if it's really bad, I'll replace it. Thanks Thunder

You should do both sides. Muratic acid overnight works wonders if your finances are tight and there is enough good wall thickness left.

Yup, I am "Boating on a Budget"! After the acid soak, do I use baking soda, or something like that to nuetralize it?

Let them soak, then run a stiff wire through the passages then let them soak some more. Finish with a thorough flushing with clean water.

The acid wash will without any doubt clean all the rust out of the manifolds, but I have gotten into troubel leaving them in the acid wash too long. What happens the acid will also eat good metal along with the bad. Often you may have to maching the gasket surfaces again to get a good seal. You will be surprise how clean you can get them with hard wires, screw drivers air then flat fise the gasket surfaces and your back in busness. As soon as you take them apart you will see the water passages restricted. And when your all done you should try to water test them . Run hot water thru them, and look inside of the exhaust ports they should be nice and dry!
Good luck and post what you finally end up doing.

Well, got a new manifold, the old one had a 01-89 casting number, pretty rough. However, I am having problems getting the new manifold on. It almost sems like it is warped, if I get the middle snugged, the outside bolts bind. Any ideas?? It's brand new. This is turning into a nightmare, should be pretty simple.

Did you only buy one manifold?
We are talking exhaust manifold correct ?
Typically you would replace both reason being if one is gone and the other is the same age it is probably in the same condition.
Lay the manifold down on a flat surface, or somehow inspect it with a straight edge. Then lay the gasket over the bolt holes. The bolt holes in the manifold should line up with the gasket. On the exhaust manifold , you may have the gasket upside down ??????

Another item I forgot to mention. The manifold is quite heavy and awkward. Occasionally I will put a stud in the motor with a slot in it for removal. Put the gasket in position, put some grease on the other end of the gasket so it lines up. The slide the manifold on and catch a bold on the other end. Get all bolts started, then proceed to tight the manifold up. Start in the middle and just snug eveything up.

Gasket lines up, I can get all the bolts started, its just when I draw it up, the end bolt on the front binds, like the hole is a little off. I shouldn't have to open it up, I wouldn't think.

Well, I got everything on, the bolts were a little long, the new manifold was a little different, so the bolts were bottoming out. But that did not fix the problem, the coolant HOSE was FULL OF GUNK!! I can't believe it, I meant to check the HOSE earlier! What a MORON! Anyway, thanks for all your help, and sometimes you don't get the WORST, even if you expect it!