Info on a K/B 6.5 Marine engine

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Info on a K/B 6.5 Marine engine

Postby James C Harrell » Tue Jan 31, 2012 5:07 am

I have a K/B 6.5 Marine engine. It has a front exhaust, rear carb, Marine head. and the throttle is a valve on the exhaust header. It has no ring, appears to be perfectly clean and has tremendous pinch at TDC. New?? I cannot seem to find any listings as far as parts, power, instructions Etc. Can you help?
James C Harrell
 
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Postby James C Harrell » Tue Jan 31, 2012 6:01 am

I figured I would try and put a piture of it up here. I am a newby here so bear with me.

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James C Harrell
 
Posts: 7
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Location: USA

Postby James C Harrell » Tue Jan 31, 2012 6:08 am

Could have made them smaller I guess. What I want to do with this is this. I have a RJL .61 airplane engine in my 36 in v-hull. It has a cool clamp on it and it does fair. I think this engine would be better. The .61 doesn't turn up like I think it needs to. A friend of mine had this engine in a box at the back of his shop and said for me to take it. Same friend that gave me the boat. Good friend!! Like I sai the pinch and appearance says it hasn't been ran much if any. Would really like to know about it and how to break it in. Thanks.
James C Harrell
 
Posts: 7
Joined: Tue Jan 31, 2012 4:58 am
Location: USA

Postby SteveM » Tue Jan 31, 2012 8:40 am

The older K&B 6.5cc inboard marine engines are solid performers and were eventually superceded by the 7.5cc version. They have a reputation for being pretty bullet proof given proper care.

The pinch at top dead center (TDC) is normal and is the result of the motor's ABC construction. ABC stands for an aluminium piston running in a brass sleeve that's been chrome plated. The cylinder bore has a slight taper towards the top which helps seal the piston to cylinder gap prior to combustion. This allows for very high RPM's.

The header with the butterfly valve can be removed and replaced with a Mac's water cooled header and pipe. The venturi can also be removed and replaced with a black or red carb. These carbs have different internal diameters and were colour coded for easy identification. There is also purple and gold versions. Black has the smallest diameter and gives the best throttle control but sacrifices top end.

I recommend you use the same fuel you intend to race with for break-in purposes. On all my K&B marine motors, I would add 1oz of Sig AA castor oil to each gallon jug of fuel. This gave me slightly better protection and my motors lasted several seasons. For my 3.5cc and 7.5cc motors I last ran Byron 25% nitro fuels. I'm not sure they still make this fuel, but something similar should work fine.
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Postby James C Harrell » Tue Jan 31, 2012 9:19 am

Can I run the same carb exhaust set-up I have now? If so what would be an exhaust set-up for it? I have a couple of different tuned pipes and can experiment with them if I could figure out how to hook them to this manifold. Maybe a standard coupler. I assume the valve on the exhaust is the throtle??
James C Harrell
 
Posts: 7
Joined: Tue Jan 31, 2012 4:58 am
Location: USA

Postby SteveM » Tue Jan 31, 2012 9:27 am

James C Harrell wrote:Can I run the same carb exhaust set-up I have now? If so what would be an exhaust set-up for it? I have a couple of different tuned pipes and can experiment with them if I could figure out how to hook them to this manifold. Maybe a standard coupler. I assume the valve on the exhaust is the throtle??


You can run the motor as shown with the venturi and the butterfly exhaust throttle. The trick is finding a tuned pipe that is a tight fit over the O-ring on the header. You would also need to use a tuned pipe support at the end of the pipe to keep the pipe from blowing off when running.

An exhaust throttle gives poor throttle though and they tend to operate more like an on/off switch when running.
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Postby James C Harrell » Fri Feb 17, 2012 3:32 pm

I've been told that the carb and backplate needs to be rotated to the top. Is there any manual or exploded veiw of this engine? Also if I needed parts for it will the parts for the 7.5 or any other engine interchange? This has a tremendous amount of pinch. More than any other engine I have had. That being said, I have only had smaller car engines of this type. I have got it to fire but only for a short period. I really don't want to damage the conrod. I rotated the backplate to the top befor I started it. If it sucks fuel in through the carb I figure it is right. Is that a resonable assumption?
James C Harrell
 
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Location: USA


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