CMB 28.5 Evo Help

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David Bryant

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Sep 7, 2011
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the engine doesn’t seem to circulate water very well. To remedy this I have swapped water lines around and it seems to have helped but still doesn’t seem right.

The water enters at the top of the head and exit out the side of the block. This is the only way I can get water to move thru the engine.

As far as timing and needle settings everything is correct.

For some reason it did burn the electrode off the spark plug the first time I ran the boat assuming because the engine got hot from lack of water running though it.
The spec of electrode that came off did make a small mark on the sleeve.

I realize this this will hurt the performance of the engine but I don’t want to put an new piston and sleeve in the engine tell the water issue is 100 percent fixed.
interesting, thanks.

As far as needle settings, did you experiment with measuring the height of the (needle) screw heads? (mentioned in a previous post?)
 

Steven Kinney

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Sep 25, 2019
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Yes I checked my needle setting before running the last time against the ones I believe you provided. They where very close. Don’t remember the number now. I richened both a little just to be on the safe side the last time I ran the boat.

Right now it seems like I just have a water flow issue. The engine didn’t over head when I ran it last but it just doesn’t put water out like every other engine I have had.
Maybe that just the way this engine works that’s why I was trying to get info from someone that has run this motor.
 

Wasted wages

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Jan 2, 2006
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Have you pulled the top of the motor off, to see if there is a piece of gasket or o-ring that could be acting like a flap, only letting water flow one direction?? or a piece of trash rolling around in the water jacket blocking the water fitting in one direction?
 

Steven Kinney

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Sep 25, 2019
Messages
116
Yup I pulled it all apart after the first time I ran it to check for damage. Even when I bench test it takes quite a bit if pressure to get the water to flow through the head.
I am guessing it’s because if so tall.
 

scottmeyers

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Jun 15, 2011
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229
Steven, I couldn't get water flow on my gas boat either until I moved the pickup holes to the right side of the rudder blade. Call Bill and get a SlyCat rudder with the pickup holes on the right side of the blade and you'll get more water flow than you'll know what to do with.
 

Wasted wages

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Jan 2, 2006
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I'm thinking the rudder pickup holes may need to be enlarged or reshaped,,,
Or if any left input is needed to make the boat track straight, it's killing the flow into the rudder holes. I've seen that happen A LOT !
 

Steven Kinney

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Sep 25, 2019
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116
Ya I think you are right Scott. The only time I could get good water flow if I am rolling. If I just mill nothing will come out.
I did try a rudder I made that had bigger inlet and exits than the speed masters and it didn’t work any better.
I will give Bill a shout and see what he has. Thanks
 

Steven Kinney

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Sep 25, 2019
Messages
116
I took a speedmaster dual pickup rudder and opened up everything up to get more water flow. I also tried a rudder I made that had bigger inlet and exit ports. Neither one of them made a difference.
 

David Bryant

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Joined
Sep 7, 2011
Messages
2,185
I took a speedmaster dual pickup rudder and opened up everything up to get more water flow. I also tried a rudder I made that had bigger inlet and exit ports. Neither one of them made a difference.
that's interesting. Tells me that the constriction has to be the CMB water fittings on the engine/exhaust? (small bore ID?). Glad you brought this to our attention, as I'm using the same engine
 

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