Overheating - Hit Rubber Raft

[riverratjody]

I have a 98 4.3L with an Alpha Gen II. I replaced exhaust manifold and riser last year and it ran great. Been out twice this year and it ran fine. It usually runs around 105 degrees, which I know is cool, but whenever it runs hotter, it diesels and won't shut down, so I left that alone. The other day I ran over a submerged rubber raft that wrapped around the drive. I heard a thump and thought it was a stump till I found the raft. It immediately shot up to about 180 degrees before I shut her down. I assumed the impeller burned up, but when I opened it up, it looked fine. I thought that maybe the impeller had separated from the hub, so I went ahead and replaced it. Still running hot. When running on muffs there appears to be a lot less water coming from the propeller than it was before. Plenty of water coming from under the drive. I found nothing sucked up, but I guess it's possible. Was the thump I heard something breaking. Help, any ideas, and thanks?

 

[Pete104]

Re: Overheating - Hit Rubber Raft

The thump was probably the raft sitting still & hitting it under power, I'm sure there would be a noise. The stump I would think you would be over the windshield. Glad your not.
How hot is it running? I'm thinking that the engine temp got hot enough for the thermostat to open fully & now your temp is actually normal.

 

[90stingray]

Re: Overheating - Hit Rubber Raft

180 wouldn't hurt anything. Should have run her as is. I would look at the impeller gaskets... maybe something got messed up? When is it overheating now? Just at idle on muffs?

 

[riverratjody]

Re: Overheating - Hit Rubber Raft

I haven't had it past idle since I hit the raft, but it has never run that hot until the instanct the raft wrapped around my drive. Yea, maybe it running at 180 for those few seconds unfroze the thermosthat and now it is running right. I don't like it this way, as I'm afraid it is going to be dieseling all the time. And, it still concerns me that a lot less water is coming from the prop than was before. Thanks.

 

[90stingray]

Re: Overheating - Hit Rubber Raft

How hot does it get at idle on the muffs?

 

[riverratjody]

Re: Overheating - Hit Rubber Raft

I shut it down at about 170 as I assumed it would continue to rise and overheat. Guess I should just let it run and make sure it does not get over about 175. Does that sound like a plan? Maybe I'm making a problem where no problem is. I will try that tomorrow and post my result. Thanks.

 

[Pete104]

Re: Overheating - Hit Rubber Raft

If I were you, take a look at the distributor cap & check the timing.

 

[nola mike]

Re: Overheating - Hit Rubber Raft

How would hitting a raft affect the timing?

 

[dn010]

Re: Overheating - Hit Rubber Raft

Make sure nothing got sucked into the water intakes and your passages / hoses are clear. Sounds like it may be blockage somewhere...

 

[riverratjody]

Re: Overheating - Hit Rubber Raft

Ok, thanks everyone. Figured I'd post my final result. Hope this is right. Ran it again on muffs today and let it run without shutting it down at what I thought was about to be hot, and it never got over about 160 or maybe 170. I measured the temp of the water coming from under the drive and it is about the same temp as it was before my incident, about 117. (Still a little concerened that very little water, and no hot water comes from the prop, but maybe that is normal.) So my final thought is that my temp gauge was stuck and would not go higher than about 110. When it had the raft wrapped around the drive, it drove the temp up to higher than it had ever been before, cauing the temp gauge to get past that old 110 mark. Now that it made it past that mark, it is working correctly. So, I guess I missed a weekend on the lake for nothing. But, sometimes I can be over cautious. At least my son says so. Again, thanks to you wonderful people offering suggestions!

 

[Pete104]

Re: Overheating - Hit Rubber Raft

Under power, the exhaust & water are coming together much sooner than running on a hose. I don't get why you prefered the lower temp!? Whatever, happy boating!

 

[Sharp Shooter]

Re: Overheating - Hit Rubber Raft

Why are you driving over rubber rafts? I can't get past that detail?

 

[90stingray]

Re: Overheating - Hit Rubber Raft

Ok, thanks everyone. Figured I'd post my final result. Hope this is right. Ran it again on muffs today and let it run without shutting it down at what I thought was about to be hot, and it never got over about 160 or maybe 170. I measured the temp of the water coming from under the drive and it is about the same temp as it was before my incident, about 117. (Still a little concerened that very little water, and no hot water comes from the prop, but maybe that is normal.) So my final thought is that my temp gauge was stuck and would not go higher than about 110. When it had the raft wrapped around the drive, it drove the temp up to higher than it had ever been before, cauing the temp gauge to get past that old 110 mark. Now that it made it past that mark, it is working correctly. So, I guess I missed a weekend on the lake for nothing. But, sometimes I can be over cautious. At least my son says so. Again, thanks to you wonderful people offering suggestions!

If it makes you feel better ... mine has no water coming out until thermostat is opened. Then very little, like just spitting out. But if you gas it, it will blow out more water. Right or wrong, that's how mine operates.

 

[BRG25]

Re: Overheating - Hit Rubber Raft

I would verify what temperature your engine is really running at. I find it difficult to believe it was running at 105, that is way too low. 160 is about right for a raw water cooled engine. I wouldn't trust the temperature gauge until you compare it to something like a IR temp gun.

Also, you should check the temp with the boat in the water. I don't think running it on muffs is very accurate because you have water pressure from the hose.

 

[riverratjody]

Re: Overheating - Hit Rubber Raft

"Why are you driving over rubber rafts? I can't get past that detail?"

Cause the raft was submerged. Thanks again everyone, as I believe you were right in that it never did run at 105 degrees, and is not running hot. An IR gun will verify. New boater learning every day. Will hit the river this weekend! Happy Boating to you too!

 

[NHGuy]

Re: Overheating - Hit Rubber Raft

And don't run over any more stuff, dammit!

I couldn't resist...

 

[mrchev]

Re: Overheating - Hit Rubber Raft

i bought my boat the end of last year it ran 160 idling in the water and 125 cruising. pulled the lower end off over the winter and found water pump impeller fin broke, changed pump and put boat in this year it stays at 125 all the time. (one mor thing do you have a temp and oil alarm on it,mine would go off when the pump was broke and idling).