79 Nautique Won’t crank once hot.

The other day I went out on the lake and ran the boat wide open for a few minutes. I pulled the boat down to a stop. The boat died. Well I replaced the battery cables and it cranked right up. Now when I run the boat, about 30mph at 1800 RPM, the enigine has a knocking sound. (I also hear the knocking sound when I rev the engine in neutral to about 1500 rpms) And when I cut the boat, it turns over put will not crank. I let it cool for about 30 min and it cranks right back up. I need advice.

Few facts I know:
    -I have not replace plugs or wires in about 2 years. I just change the oil impeller.
    -I didn't knock before I ran it wide open.
    -My oil pressure gauge reads almost 0 all the time. I really think it read like 40 0r 60 before, but I'm really not sure.

a) What do you think the engine knocking is from?

b) Why do you think the boat will not recrank when shut off while warm/hot about 180 degrees.

Thank you very much for helping me with my problem.

Georgia Fan

Hmmm....here is a thought: Since you are running the engine with out oil pressure, your valve lifters are not pumping up and you are hearing the resultant clatter from the slop in the valve train. Also, I suspect you are siezing the engine.

Hopefully I am wrong, but whenever an oil pressure guage reads zero, you shut down the engine immediately and determine the cause and repair before running the engine again.

Not sure on a Ford engine, but once I rebuild a Chevy and purchased a new oil pump complete with pick-up tube. After a few miles of driving with the freshly rebuild engine, I heard a noise in the engine and my oil pressure idiot suddenly illuminated. Before I could safely pull of the freeway, the valve train started to clatter. Since the Chevy oil pump is driven off the bottom of the distributor, I immediately pulled the distributor to inspect this connection. I found one of the ears broken off the pump drive shaft. So, I had to pull the engine to replace this shaft and inspect the cause. Turns out that during manufactur of the oil pump pick-up, someone had simply hack sawed the tube the length and did not de-burr the cut. One of the burrs dislodged from the pick-up and jammed the oil pump gears. Needless to say I inspect all new oil pump before installation from that day forward.

Now I believe the Ford oil pump is driven the same way, but via a hex rod/socket not a tab and slot like the Chevy. Pull the distributor and inspect this connection.

Check your oil pressure with a gauge to make sure it is infact low. Or, replace the sending unit ($15). Replace with a marine unit...the automotive ones won't work properly. Stupid question, but you checked the oil level, right? You may need to replace the oil pump.
If it's got curdy valve stems, would anyone suggest running B-12 Chemtool through the crankcase?

Not in my crankcase!!!! However, when we were kids building hot rods, if we had a gunked up engine we would pour a quart of varsol in the crank case, run an hour and drain - I'm smarter than that now. (I think.)

Let us know what happens Georgia Fan.

(But then, if I was about to spend $3500 I might pour anything into the crank case to see if it helps - Olive Oil, Jack Black, or even Draino, if I thought there was a chance....)

Sorry Jimbo, I just had to poke fun...


But I really would pour all kinds of stuff in my engine if I was about to spend $3500 on it - I might even follow the Draino with a bag of Portland Cement.

Hehehee. I don't know what it is with people dumping stuff into the oil pan other than oil.

My sister's kids like to drop rocks down into the cities access to the water supply. Maybe its the same thing.

I've only used engine oil flushes twice, and one time it was a doozy. It sped up the fact that the motor hadn't been reassembled properly by the guy that rebuilt the engine. We were just getting ready to sell the thing, too.

Older motors like these, there is no harm in using 50w. Diesel trucks like it, so do old motors. Heck, I used to use 20/50 in a 2.5 four cylinder I had and it loved it. So much for what it said on the cap (5/30) That motor went 230K miles with me beating on it.

I believe the newer ones are specificaly designed for 5w, so if I had a new car, I'd use it. As for my older war machines, its 10/40 or 20/50

I concur, and perhaps put in a 'rebuild engine' dash light, because the oil pressure gauge was ineffectual.