CD-10, Too Hot?

[raglover]

Running a new to me cd 10. Had a few of the cd’s and ad’s over the years and seem to recall burnt paint on the exhaust plate cover on the side of the power head was not too uncommon….maybe that is a bad recollection. Here is a question asked a lot, sheepishly asked…am I running hot?

Mine has new pump and pumps a lot of water. Powerhead seemed a bit hot to touch, after about 1.5 mins of running…hard to hold a 3 count bare handed, my official check. Did not boil water though.

Here are vitals
Compression is good and even, 95 psi, no con rod slop.

After cooling, removed flush plug and restarted, pumps tremendous water.
Pulled power head, gasket matches correctly, afraid I may have mixed with 6 hp version which I think is different for t stats.
Passages look clear from bottom, is freshwater motor.

Exhaust gets hot IMMEDIATELY at start up..less than 10 secs. Should I pull plate and look for blockage or build up? Worried about breaking screws and want to avoid if possible.

Is this normal sounding for the early cd motors? Seems my last had scorched paint but was fine and ran great. Secondary question, was the flush screw meant to allow motor to run while flushing or just while not running?

As always, thank you!

[Mumbles]

Your ’54 Johnson is acting normal and seems to be in excellent condition with 95 lbs compression. The non thermostat 5.5’s don’t have a water jacket under the exhaust cover like the ’59 and later motors do and the cover is exposed directly to the fire and flame in the exhaust gases. Three horse motors are designed the same and that’s why the paint scorches. A little trick I use to prevent this on restored motors is to install a ’59 and later inner exhaust plate to prevent the hot exhaust gases from burning the paint. Three seconds is a long time to hold your hand on any motor and with all of the water being pumped, I’d say it’s OK.

I’m pretty sure ’54 was the last year for the removable flushing plug while the 55’s used the same casting but it wasn’t machined to accept the plug. OMMC offered a pointed rubber attachment which fit on the end of a garden hose which could then be used to flush the non running motor thru the plugs hole.

[dan-in-tn]

You mentioned ADs which have water cooled exhaust covers already. They should not suffer from burnt paint on the covers unless something is wrong. Just to clarify.

Dan in TN

[fleetwin]

Kinda hard to say for sure I guess. Like Mumbles says, the exhaust cover will definitely get hot pretty quickly. Where are you doing your temp tests? Try your finger test on the stbd side of the block, not the head, how does that feel?
There are three different base gaskets used on the CD series, the wrong one will cause an exhaust leak into the cooling water under the powerhead…What part number base gasket did you use?

[raglover]

Thank you all. First I mis-spoke in model, it is a cd 12, 1955. Has the hood with the two wing nuts on the front side, so I guessed wrong.

I was feeling cylinders on the head and side of block behind the head opposite the exhaust. Also top of block. For some reason second guessing on this one.

For part number, actually used sierra 18-2894-9 as replacement for304314. Hope that is right, marine engine only starts parts diagrams for cd-14.

[Mumbles]

You want the ’54 – ’55 303467 base gasket, not the 304314 one. Using the later one will give you an internal cooling water leak. The motor will have lots of water at the flushing port but will be leaking into the exhaust housing on the inside. Your CD-12 must be an early one with the thumbscrews on the hood and a flushing plug installed.

Here’s the two different gaskets for comparison. The 303467 one is the top one.

[dan-in-tn]

Well! I can’t remember if I learned something today or re-learned something today! Ever have one of those moments? I have put on the site incorrect info about CD motor base gaskets. If I can find it, I will edit it. Just beware I have mislead someone out there. Sorry!

Of course the #303467 is the one Sierra doesn’t make! And the most expensive. I believe I remember that.

Dan in TN

[raglover]

Wow, thanks for the update on the gasket, never would have known and the old one was too far gone/ did not think to compare.

Will change that asap.

[fleetwin]

Cool, hope this resolves it…D

But, while we are on this topic….
Why the heck are there two different gaskets for the 56-58 models, and all the later thermostat models?
My weak eye indicates the gaskets are really the same, one just has more of the water inlet passage covered, allowing water through just a small hole in the gasket. And, again, my tired brain would think that the restricted gasket would be used on the non thermostat models, but the opposite is the case….
Any thoughts?

[Mumbles]

I don’t know why they use the 313065 restrictor gasket on the T Stat models but I would think the water tube alone would be more restrictive than the hole in the gasket. BRP might have realized this as some six horse 313065 gaskets I bought from the dealer didn’t have the small hole and were identical to the ’56 – ’58 304314 gaskets. I guess it’s possible they could have been packaged wrong to but switching them around doesn’t seem to affect the operating temperature or water flow in the motors. The motors can’t tell the difference.

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