31' / 327Q questions

31' / 327Q questions

Joined: October 17th, 2008, 6:09 am

April 22nd, 2009, 7:04 pm #1

Hi all.

Mechanical repairs are progressing. Costly, but the boat is running again.

The port engine, which overheated at the end of the first day of ownership, was found to have an impeller with no blades on it. New impeller ordered and installed, and voila!, we have water 'surging' through the exhaust outlet at idle. Temperature is normal (the dot between 60 & 160 on the temp gauge, which is the same as the starboard engine).

However, when taking the boat out for a mechanich's review of the performance, the port engine temperature rose significantly, to the point of overheating.

After letting it cool, and refilling with 50/50 coolant (complete refilling), I ran the boat for several hours and learned that I could run around 2200 RPM and just stay ahead of the overheating situation. Anything faster, and the temp increase overcame the cooling systems ability to compensate. Anything below, and it cooled faster than it could get hot. I did notice that when running, there was way more steam coming from the port exhaust than the starboard exhaust, which corresponded to the higher temps on the gauge.

The mechanic thinks there's bits and pieces of the missing impeller partially clogging up the plumbing, and thinks it is going to be back around the heat exchanger & T-Stats on the risers. I've read another blog where it's mentioned to remove the cover from the transmission reverse gear oil cooler.

Comments? Where are we likely to find the remnants? Also, what happens if the impeller was installed with the blades bent/twisted in the wrong direction?

What is the factory WOT RPM for the 327Q engine?

Also, looking at my CC Thermocon Engine Ops Manual, it doesn't say what WOT/Max RPMS for these 327Q's should be, but does mention 3200 RPM for max torque. I did get to run it WOT a few times for about a minute to see what kind of engine speeds I could obtain at proper trim. I think I saw as high as 3200 RPM one time, but mostly around 3000. No idea on speed, but we guestimate mid to upper 20's. Maybe low 30's. Will have to get a GPS for that.

The mechanic said the motors sounded and felt strong, but that he wanted to do some adjusting on the 'older than dirt' Holley carbs. When the starboard engine is running, it smells like it's very burning a very rich fuel mixture.

One more thing. When my throttles are in identical positions, the starboard engine is turning more RPMs, sometimes considerable more, than the port. Is this likely a cable / linkage adjustment?


Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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Mark Weller
Mark Weller

April 23rd, 2009, 1:07 am #2

Kevin look at the trans cooler it is the first thing after the raw water pump and it is "screened" to prevent the impeller blades or other debris from going any further. Holley carbs on a Q say it aint so!! The difference in the throttles should be adjustable at the carbs and possibly at the levers depending on what type of controls you have.
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Joined: October 17th, 2008, 6:09 am

April 23rd, 2009, 2:12 am #3

Thanks Mark. Great information.

What should these motors spin up to, assuming that the props, etc. are all stock?

I've read enough good things about the Edlebrock 1409's that I plan to, in the not too distant future, to replace the Holley's with Edlebrocks.

Got the news my new Centek mufflers are in. Pretty excited about getting the mechanical bugaboos taken care of.

Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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Joined: October 17th, 2008, 6:09 am

April 23rd, 2009, 5:30 am #4

Found it in the Ops manual. I've got another 1000 RPM to find in the boats performance....technically speaking.

Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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Kevin
Kevin

April 23rd, 2009, 12:33 pm #5

I recently spoke to a gentleman who is the oringinal owner of a '70 31 SF with 327's. He stated that his max rpm's are 3400. He stated that it has always been that way and he claims he has the oringinal props that came with the boat.

The question is, what damage can be done to an engine after so long a time not being able to get to max rpm? My assumption is that he runs the boat about 2800-2900 for cruising since he is on plane.

Kevin
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Paul
Paul

April 23rd, 2009, 2:36 pm #6

It depends on how it was run, who was running it, and what kind of maintenance program (and oil) was used.

As with vintage Porsches and boats, "condition" is always more important than age or engine hours. If the motor tests out with good compression and oil pressure, hey, then run it responsibly.

The history of the boat is unknown unless you find the previous owners. If they putt-putted around all the time, then the wear factor would be vastly different than someone who ran it hard all the time, with an hourmeter not knowing anything about it.

As a rule, your props should be sized to allow the motors to reach maximum engine rpm. I don't have the spec for your boat right on hand, but it should be reasonably easy to do so, and that is a starting point. If you have twin engines, be sure to recognize that and not use a prop size that would have been specified for a single (the 27' Commanders have to be concerned about that). Also, if you have a 31 SE, for instance, or even an early 38 Commander, the prop used with a 210-hp 327F is vastly different than what would have been specified for the 431 or 427.

Let's first find out what the stock prop is for your particular boat and power, work from there. In addition, you never know what was done to the boat in the way of mechanicals over the years. With the SBC motors in particular, there are so many cylinder head combinations, you run a risk of having someone install some TAXI Cab heads onto a Q motor, for instance, and I would rather have the Q heads on a Q motor

Just a few thoughts for the morning.

regards,

Paul

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Tim Toth
Tim Toth

April 24th, 2009, 12:59 am #7

I recently spoke to a gentleman who is the oringinal owner of a '70 31 SF with 327's. He stated that his max rpm's are 3400. He stated that it has always been that way and he claims he has the oringinal props that came with the boat.

The question is, what damage can be done to an engine after so long a time not being able to get to max rpm? My assumption is that he runs the boat about 2800-2900 for cruising since he is on plane.

Kevin
Kevin,
The 31 Commanders with 327 engines were equipped with 15x17 wheels ,no cup when they left the factory. You can verify this by calling the Mariners Museum Chris Craft archives located in Va. Give them your hull # and purchase a copy of the hull packet that is for your boat which "will have" the "original"prop size listed.
Tim
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Joined: October 17th, 2008, 6:09 am

April 24th, 2009, 5:04 am #8

Kevin look at the trans cooler it is the first thing after the raw water pump and it is "screened" to prevent the impeller blades or other debris from going any further. Holley carbs on a Q say it aint so!! The difference in the throttles should be adjustable at the carbs and possibly at the levers depending on what type of controls you have.
Well. We found ALOT of the old impeller in the input screen of the oil cooler. However, no change on the overheating condition. If we run it more than 2200 RPM, it starts to gradually overcome the cooling capacity. Starboard Engine is fine. Any suggestions as to where else to look for blockage?

Has anybody out there accidentally installed the impeller with the blades bent in the wrong direction? What happens when that occurs?


Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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Tim Toth
Tim Toth

April 24th, 2009, 11:45 am #9

Kevin,
Pull the t-stat housing and check for blockage there also and test the t-stat in a pot of hot water with a thermometer to check correct operation.
Remove the distributor cap first before pulling the t-stat housing.While you are down there tighten the sea water pump belt and alternator belt .
Tim
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Joined: October 17th, 2008, 6:09 am

April 24th, 2009, 4:19 pm #10

So I've found what I think are about 1/2 of the missing blades. They were at the screen on the oil cooler. I'm wondering if the rest of the blades are lodged in the hose between the pump and the cooler. All that came out of the pump was the hub with no blades.





Thanks!

Kevin Bray
'06 CC Launch 22
FXA-31-4049
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