Boat question.

[Davey Crockett]

So I bought a 1988 Lund Baron with an Inboard 4.3. V-6 Very nice well kept boat and the seller has a mechanic shop and I was assured the boat has low hours and no issues.

First trip out I idled around for a while and watched the gauges all normal, Throttle up on plane and went about 1/2 mile Gauges still normal then throttled up for a 100 yard dash to my fishing spot and when I throttled down it had a miss and made an internal sound almost like the exhaust on a vehicle with a bad valve. Gauges still normal.

Shut it off and trolled for an hour and hit the key and it purred like a kitten. Idled around, No issues, got up on plane about 1/2 mile and it did the exact same thing so shut it off and brought it home and found 4-1/2 quarts of water in the oil that wasn't in there before so I drained/changed and put muffs on 1/2 hour everything normal so put it in a tub of water so it can warm up to normal operating temps and that internal noise comes back but it's so "internal" that I cant detect where it's coming from, I didn't run it long enough for it to contaminate the oil.

I called the guy I bought it from to verify or confirm that it had been drained properly even though when I called about looking at the boat I was told the drain plugs were out and needed to be put back in. Seller has a mechanic shop and he seemed just as surprised as I was about the whole deal and he was going to ask around for ideas of what it could be so I called him back this morning and half ways through the conversation he said he had to take care of something and would call me right back, 6 hours later he hasn't.

Stills idles flawlessly on muffs for long periods of time with no issues. Anyone have ideas what might cause this ?

 

[2400]

Shut it off and trolled for an hour and hit the key and it purred like a kitten. Idled around, No issues, got up on plane about 1/2 mile and it did the exact same thing so shut it off and brought it home and found 4-1/2 quarts of water in the oil that wasn't in there before so I drained/changed and put muffs on 1/2 hour everything normal so put it in a tub of water so it can warm up to normal operating temps and that internal noise comes back but it's so "internal" that I cant detect where it's coming from, I didn't run it long enough for it to contaminate the oil.

You didn't mention where the water came from, engine cooling system, lake, beer cooler, or??

Did the water/oil mixture look like milkshake or was the water floating on the oil and clear?

 

[Davey Crockett]

Drained when I got home it looked like cream colored thick grease, I've not warmed it up long enough to contaminate the oil a second time.

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Lake water , This is an open pump and dump open water cooling system. No antifreeze or heat exchanger.

 

[eyexer]

pull a plug and see if there is any water on em. you might have a cracked block that involves the intake/combustion chamber/crankcase. My kid just bought an IO with less than 100 hours on it. Had three cracks in the block because it didn't get winterized properly. He had two of them brazed and they are holding fine. The other is behind the intake and that has to be pulled off. But it's such a small seep that we're gonna roll with it till winter. Def. brought the purchase price down lol.

 

[Davey Crockett]

Eye, Were the two cracks he had brazed external leaks ? And is that V-6 GM ? I ran it a long time with the muffs after the oil change so I figured I'd have to duplicate the good warm up scenario before I pull the plugs since they are a bearcat to get at. I had to walk away from it for a while.

 

[Allen]

Sorry man, you will want this.

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At that volume of water, she has a bad crack somewhere. Head, block, intake, ??? sounds like you are literally pulling in so much water on top of the piston to create that "internal" sound.

 

[Davey Crockett]

I'm not sure if I will get the shaft or not but I'll go down swinging if I do , Such nice people I just have a hard time believing it. Unreal that it will run cold with no noticeable issues but at normal operating temp it turns into a gusher. I honestly don't believe a cylinder could pull that much water without hydrolocking or knocking but I've been wrong before and I have a boat to prove it.

 

[shorthairsrus]

Still cheaper to replace or repair then an overpriced outboard

 

[dkbigsky]

I would bet its your exhaust manifold. Might be cracked, easy fix but might cost a little to get it brazed. Happened to me. I drained it in the fall then put the plugs back in so I didn't lose them and there was enough left in it to crack the manifold

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There is a water line that cools the exhuast

 

[eyexer]

Yea they were external cracks on outside of block at the water jacket. It’s an in-line four cylinder merc.

 

[Davey Crockett]

Still cheaper to replace or repair then an overpriced outboard

Yea that's the good thing, And the reason I like inboards , I can get a reman. 4.3 marine long block delivered to my door for less than $ 2000 . But the timing is never right , I was going to be at Sakakawea this morning . I should have tore into it with hopes of finding a gasket or a manifold like dkbigsky says. The important thing with inboards is a good drain down in the fall , I wait and watch water come out every hole and then stick a piece of wire in every one just in case there is a blockage .

Eye , That gives me hope.

 

[SDMF]

I don't know diddly squat about inboard motors other than I hear improper fall draindown can be a problem and hard to accomplish.

Is there no sort of fitting one can attach to an air source to blow things out?

 

[Davey Crockett]

I think the key is making sure the engine is sitting level and watching to be sure theres no drain hole blockage . I pull the thermostat cover and pour some rv antifreeze back in just so I sleep better at night.

 

[eyexer]

I told my son when it comes time to winterize we're pulling the lower unit and the thermostat. Then dump RV antifreeze down the thermostat housing till it comes out the bottom lol

 

[johnr]

Good luck with everything, unfortunately the guy selling it is not on the hook for anything, private sale is always an “as is where is” deal. Buying used comes with no warranty.
Again best of luck

 

[LBrandt]

I have a stupid question. Inboard engine suck lake water in and out like an outboard?

 

[eyexer]

Yep. Exactly the same

 

[Davey Crockett]

I would bet its your exhaust manifold. Might be cracked, easy fix but might cost a little to get it brazed. Happened to me. I drained it in the fall then put the plugs back in so I didn't lose them and there was enough left in it to crack the manifold

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There is a water line that cools the exhuast

By hookey You were right , Not sure if that is the extent of the problems of but I pressure checked it with bubble solution and there is an internal crack above # 3 exhaust port. It leaked so bad that I was able to blow the solution right out of the manifold . The first thing I did was pressure test the water jacket and found a soft plug below # 3 was pushed out. That scares me but it might be a blessing too if it released pressure and saved the block. I'll pressure test it again when I get new soft plug in. Borescoped all the cylinders and heads the best I could and the only thing out of the ordinary was a red film of surface rust on # 3 exhaust valve stem and seat and around the ridge inside # 3 cylinder. 135-140 compression all the way around . $190 for new exhaust manifold, Comes with new bolts , gaskets and fittings . It's worth taking a chance and putting it back together at this point and trying it again. If its toast I'll still take it fishing and order a reman long block for $ 1650 delivered to my doorstep. Those little Chinese borescopes are worth their weight in gold.

 

[Downrigger]

Reading this post puts me in awe of you guys and your abilities.

Also makes me want to turn in my man card.

 

[Davey Crockett]

Reading this post puts me in awe of you guys and your abilities.

Also makes me want to turn in my man card.

It's all what you grew up with and around and what you liked doing. I'd turn in my man card before I'd do a lot of things. Especially math and carpenter work.

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I smile when I see kids helping dad fix things no matter if its a lawn mower or a race car .