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Message |
    
Russ Murray
New member
Username: russ
Post Number: 2
Registered: 10-2009
| | Posted on Friday, October 23, 2009 - 03:46 pm: | 
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With the help of this forum I found the serial number so now know that I have a QXB-5M Sea Flyer. According to the published specs it should put out 65hp at 3500rpm. That seems really low for 205ci but the compression ratio is shown at only 5.85:1. I have records of a fairly recent rebuild and have talked to the shop where the work was done so I think it is in pretty good condition. I have run it but not in the water. Starts and runs but does not idle well.
My question/concern is whether I will have enough power at 6,000ft above sea level in Colorado to even get my 17' Split Cockpit runabout on plane. I figure the carbureted engine will lose about 18% at 6,000 feet so it is down to about 52hp.
I have talked to one owner of a Chris Craft MBL (330ci/158hp) who had a shop work on that engine so that it was boosted to about 250hp through a combination of camshaft and head work. Anyone have any ideas for what might be done to the Sea Flyer without major effect on reliability and longevity?
Second question? There is what appears to be a "resistor" mounted on the bulkhead and wired between the positive terminal of the coil and the distributor. (see pic) I have not seen such installation and someone indicated that different coil would do away with the need for the resistor. Any ideas here.
Thanks to all.
Russ  |
Scott Noseworthy
Senior Member
Username: scott_n
Post Number: 121
Registered: 02-2008
| | Posted on Friday, October 23, 2009 - 05:04 pm: |
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it mite have a 6v coil in it thay started life as 6v I have the chris craft KLC same engine bigger carborator and I balenced the pistons and rods.the engine is in a 1955 18 foot chris craft holoday it will do 35mph |
Russ Murray
New member
Username: russ
Post Number: 3
Registered: 10-2009
| | Posted on Friday, October 23, 2009 - 05:26 pm: |
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Thanks Scott. I'll check the coil when I get home and see if there is any voltage indicator on it.
I only wish I had the KLC. It is 236ci and 120hp as compared to the "Flyer" at 205ci/67-75hp. That ratio of ci to hp makes no sense to me and I'll add the "balancing" to my list of what to do. You may also be at a lower altitude which keeps the hp closer to the original specs.
Thanks again. |
Ernie
Senior Member
Username: ernie
Post Number: 1087
Registered: 01-2002
| | Posted on Friday, October 23, 2009 - 06:15 pm: |
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As to the ignition resistor
I assume you are you running a 12 volt system?
If you are running 6 a volt system it should NOT be there and will cause all sorts of running problems.
As to changing or getting rid of it with 12 volts. The ignition system has to have a resistor. You can get a coil with an "internal" resistor to eliminate the extra part which will clean up your installation. As far as how it runs it won't make a difference if it is external or internal.
As Scott mentioned to change a 6 volt ignition system to 12 volts all you have to do is add the resistor. |
Russ Murray
Member
Username: russ
Post Number: 4
Registered: 10-2009
| | Posted on Friday, October 23, 2009 - 06:28 pm: |
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Thanks Ernie.
Yes it has been converted to 12v. Sounds as if the resistor must have been added at that time as the less expensive alternative to a new coil. The installation looks a little j-rigged. Looks like a new coil is in my future as I would like to clean up the "engine room".
Thanks. |
Richard A. Day Jr.
Senior Member
Username: richardday
Post Number: 824
Registered: 11-2003
| | Posted on Saturday, October 24, 2009 - 01:03 pm: |
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On my 455 Olds marine conversion I chose the external resistor approach and a key switch with two extra contacts. One closes the field circuit of the alternator when the engine is running and the other contact simply by-passes the resistor and puts 12volt on the coil. As soon as the key is released the resistor bypass is removed and the coil operates as a normal 12 volt coil with external resistor. System never failed me in 20 years of operation. |
Jim Staib
Advanced Member
Username: drrot
Post Number: 43
Registered: 09-2008
| | Posted on Saturday, October 24, 2009 - 05:27 pm: |
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Chances are that your marine conversion will fit on Chris-Craft k series engines. They are based on the Hercules QXD/QXLD blocks. 3 7/16" bore. 95-131 HP. |
Russ Murray
Member
Username: russ
Post Number: 5
Registered: 10-2009
| | Posted on Monday, October 26, 2009 - 04:20 pm: |
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Jim, Okay, this is my third time trying to respond and I am not sure why my posting is not appearing. Maybe it is too long.
Is your suggestion that I change out my Sea Flyer for a CC K? If possible, I would like to avoid that primarily because of the cost (The existing engine was just rebuilt.) and I am not sure an engine that is even an inch longer will fit.
What I have is a QXB5M which seems to be consistent with a short-lived CC "H". The CC H shows the same bore and stroke as the QXB and indicates 75hp at 3200rpm. The next designations are K/KA with a bore increase to 3 3/8 with 85hp/95hp at 3200rpm/35/rpm respectively and no indication of how the additional hp was achieved. (see attached pdf) After the KA is another K with the bore/stroke that you mentioned but with the weight increasing from 600 to 666 which is why I thought it might be a little longer.
Anyway, I need to get this boat into the water and see what I have and then decide whether to swap or to "enhance".(cam-porting-head?) That is now months away so I am probably a little (lot) ahead of myself.
Thanks so much for your input.
Russ |
Jim Staib
Advanced Member
Username: drrot
Post Number: 44
Registered: 09-2008
| | Posted on Monday, October 26, 2009 - 05:06 pm: |
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That or put your conversion on a K series long block. |
Russ Murray
Member
Username: russ
Post Number: 6
Registered: 10-2009
| | Posted on Friday, March 06, 2015 - 05:52 pm: |
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The 31 split-cockpit has been a larger project than I had thought(aren't they all?) and boat not yet in water. I am working on the dash and the original 3-guage cluster had/has an unusual "barrel" (horizontal) tach which was the only missing piece when I purchased the boat. Have now located one with Mark Clawson but in looking at the Sea Flyer not finding a mechanical connection for a tach. This was a repower from the original Gray 4-cyl so maybe that is why no installed tach.
Anyone have an idea or pix of what/where the tach connection should be? |
Russ Murray
Member
Username: russ
Post Number: 7
Registered: 10-2009
| | Posted on Friday, March 06, 2015 - 06:17 pm: |
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Tach connection location. Thought I had looked pretty carefully last week but not too much light where boat is stored. I have a CC manual that indicates on the CC version of Kermath/Hercules to find tach connection at bottom of distributor shaft. Will be taking another look this weekend. |
Chris Craft Engine Series
