Worst boat buying fear come true ADVICE Please

**teamseal** · 10-15-2010, 02:58 PM

Overheated condition + no exhaust flapper = sucking water into motor!!!

**ToFastToCare** · 10-15-2010, 08:06 PM

Really, its that easy with no flapper? The risers are 2 ft above the water line, there is no where for the air in the engine to go, and there is a box where the exhaust pipes come together. I would think the box would dampen any wave of water that came rushing in. The air in the motor would have to be compressed too.

If I was doing 30 mph when the engine died and then the boat slowed down and the wake rolled into the back of the boat water can get all the way up into the engine. Is that what could have happened?

**slob02** · 10-15-2010, 09:10 PM

I agree with the "sucking water into the motor" thought too. I have seen a motor over heat (bad impeller) and do it. I don't know it did it though. Luckily we pulled the plugs and shot the water out. That thing ran for years after!

**horkn** · 10-17-2010, 11:01 AM

Originally posted by slob02 View Post

I agree with the "sucking water into the motor" thought too. I have seen a motor over heat (bad impeller) and do it. I don't know it did it though. Luckily we pulled the plugs and shot the water out. That thing ran for years after!

Mine did the same.

Drained the water, drained the oil, new impeller, and it was fine.......I even pulled the heads a couple years later to inspect everything and it was 100% good, even compression was fine with the old heads. While I had the old heads off I installed GT40P's , performer intake and all gaskets, and it's even more fun now.

Didn't PCM offer chevy motors even back in 95-96?

When my impeller went, every single vane shredded off. Now I replace the impeller every 3 years regardless of how it looks.

**ToFastToCare** · 10-17-2010, 05:09 PM

I am considering changing the oil, filter and getting a new impeller since other people in my situation have had success after an overheat. I am just skeptical that the engine is ok because it was and is locked up unless there is hot water in the block. Did the people who had their engine overheat also have it lock up? The engine turns 1/4 turn then gets harder to turn and then easier. My thought is there is something bent or the a piston skirt is scored causing an increased amount of torque to turn the engine at a point.

If I start it I am afraid I will do more damage and run metal through the engine.

**LT206** · 10-17-2010, 05:57 PM

Are you using the starter to turn it over? Are the plugs in or out when you turn it over?

**ToFastToCare** · 10-17-2010, 07:00 PM

The plugs are out and I have only turned it over using a ratchet on the crank bolt.

**LT206** · 10-17-2010, 08:14 PM

Well if the plugs were in I'd say that the reason it was hard to turn was because of the compression of the cylinder. You mentioned locked up unless hot water was in the block. I'm not sure what good the hot water in the block does for you. Once it's cooled off it should no longer be locked up and should turn. Turning it by hand will be hard - plugs in or out, but harder (if not impossible) if they are in.

You also mentioned a bent piston skirt or something else.... I think this thing has gotten in your head and you are over worrying - believe me I get it. I've been there too. Again, I say you haven't permanently damaged this motor and should get it running.

**ToFastToCare** · 10-17-2010, 11:11 PM

I think the hot water helps it to turn over because it heats up the bore in the block and expands the metal. The pistion is cooler and does not expand as much.

**2gofaster** · 10-18-2010, 06:16 PM

Originally posted by ToFastToCare View Post

The engine turns 1/4 turn then gets harder to turn and then easier.

Most engines will do this due to the spring pressure as the lifters go up the ramps of the cam lobes. Not necessarily anything to worry about.

**tdc_worm** · 10-18-2010, 07:14 PM

Originally posted by teamseal View Post

Overheated condition + no exhaust flapper = sucking water into motor!!!

please educate me here, but i do not think this is physically possible. an engine is an air pump. as long as the engine is rotating in the appropriate direction, it is pulling air through the intake, into the cylinders, and pumping it out through the exhaust. the flow of air is controlled by way of cam and valve events.

for the sake of argument, lets just say the exhaust was under water when running (which is not true at 4000 rpms), it would have to suck water from below the water line, up through the exhaust, and back down into the heads. in a 4 stroke engine, the rotating assembly would have to turn two full revolutions for every exhaust stroke, meaning that the engine would have to turn backwards twice to get water in all four cylinders, and that is assuming that the exhaust volume is less than 5.7Ls, which is highly unlikely. that would mean you would need several reverse revolutions to pull water into the engine.

since we know that the exhaust is above the water line, and on the aft of the boat, we can rule out that route of entry. also, if that were a known issue, why do several manufacturers offer stainless steel (flapper-less) exhaust? why would i/o boats not use flappers in the outdrive?

**ToFastToCare** · 10-18-2010, 07:52 PM

Spring pressure can play a role in how the engine turns over, but it should be equal torque to turn the engine over. The spring pressures are divided up evenly throughout the 360 degree rotation of the engine. I am fairly certain I should be able to overcome any valve spring pressure using a 1/2" ratchet, which I can't, indicating something is sticking.

**horkn** · 10-18-2010, 08:14 PM

I think you really should try and get it dried out, new oil and get it running. More damage can be done if it is not properly dried out by getting it up to operating temps and oil flowing where it is supposed to be.

If it is truly messed up, you will find out one way or another.

FWIW, my boat has exhaust flappers and my hydro locked motor, once all the plugs were out and the oil changed, turned over just fine.

**2gofaster** · 10-18-2010, 09:12 PM

Originally posted by ToFastToCare View Post

The spring pressures are divided up evenly throughout the 360 degree rotation of the engine. I am fairly certain I should be able to overcome any valve spring pressure using a 1/2" ratchet, which I can't, indicating something is sticking.

I have to disagree with this. I owned a race shop that built drag race engines for a lot of years. The spring pressures are not divided up equally because there are points within the rotation that you will have multiple valves on an opening ramp and a closing ramp at the same time. This causes you to have points where the torque required is high in comparison to a point 15 degrees in front of or behind. It can EASILY take a considerable amount of torque to rotate through these points with multiple valves on a ramp. On an engine with a conventional tension ring set, a 3/8 ratchet may not have a long enough lever arm to rotate through without effort. To check if it's the reciprocating assembly binding, the easy way is to loosen the rockers so the pushrods aren't transferring the cam lobe motion to the valves.