1994, Merc, 7.4L bravo 1-raw water pump

[haz1]

I was looking at buying a boat. The boat itself was in good shape and well cared for. The seller was confident in the boat and sincere. He had just got it from the marine shop from un-winterizing and hadn't put it in the water yet. We started it on the muffs and it sounded fine. Then I noticed a coolant leak. More by feel than anything it looked like the raw water pump case had cracked. I'm sure this would have been from freezing damage. He ensured the boat was winterized by the shop (I believe him). Would it be as simple as they just didn't pull the hoses on the raw water pump? There was no other signs of leaking. I figured if the block was cracked there would be water shooting everywhere. Oil looked good but wasn't run for very long to show any signs of water.

The seller said he'd take it back to shop and have the problem fixed. I plan to return next weekend for a test drive and buy if everything works out.

I'm wondering what else to look for. I've got more experience with OB's than I/O's, so a couple of dump questions:

1. the raw water pump is belt driven right
2. what should the engine temp run at. I'm thinking ~180.
3. Where does the exhaust and cooling water dump out on an I/O?
4. Is there an alarm buzzer that comes on if the key is left in the on position for a certain amount of time? I know a buzzer went off and wondering if it was temp related due to the cracked water pump. Water should be pouring out the exhuast outlet (where ever that is) even if it just on the muffs without the engine running correct?

any help is appreciated.

 

[valkyr]

Re: 1994, Merc, 7.4L bravo 1-raw water pump

I've got an 88-89 7.4L Mercruiser so it could be different but:

1. the raw water pump is belt driven right
Correct

2. what should the engine temp run at. I'm thinking ~180.
I believe thats correct, though probably lower on muffs as water tap water is usually cold...Mine stays around 160 or less

3. Where does the exhaust and cooling water dump out on an I/O?
Mine is behind the drive - if the drive is trimmed all the way down, the exhaust comes out of the back of the boat directly behind the cavitation plate

4. Is there an alarm buzzer that comes on if the key is left in the on position for a certain amount of time?
Mine has a buzzer that comes on if the key is on and the engine is off.

5.) Water should be pouring out the exhuast outlet (where ever that is) even if it just on the muffs without the engine running correct?

No mine doesn't. The water only comes out if the engine is running and pulling water up through the drive and into the engine. Otherwise it just sprays all over the back of the boat.

 

[QC]

Re: 1994, Merc, 7.4L bravo 1-raw water pump

Need to know if this is a fresh water (closed cooling) or raw water (open) cooling to answer the temp question. If this is fresh (closed cooling) there will be coolant as opposed to water circulating IN the engine, it will have a radiator type cap and overflow bottle.

It should get up to operating temp in either case on muffs. 160ish with raw 180ish with fresh or closed cooling . . .

If you have thru transom exhaust, your water will exit there, thru hub, there. valkyr is correct, none will get into the engine, so none will come out if the engine isn't running . . .

 

[haz1]

Re: 1994, Merc, 7.4L bravo 1-raw water pump

This is a raw water (open) cooling system. So as you suggest, temp should be ~ 160ish

I think that answers most of my questions guys, altho still a little confused about the exhaust/cooling water exit-I'll go look at one and figure it out.

Still not sure what to think about the cracked raw water pump housing. Any comments - is this a fairly common incident?, should I be concerned for the rest of the motor even if it seems to operate fine?