HD25 cyl temp

[Rick Robbins]

Checking the cyl head temp on both cyl and getting a reading with a temp gun of around 200 Deg. Not knowing what it should be, I shut it down as it seemed excessive. I just put in a NOS rubber pump part and had the head off looking for obstructions, as well as checking for blockages in the water tube going up to the block. When I pull out the plug at the bottom of the head, water just dribbles out. I just am asking if anyone knows what temp it should run at in a barrel? Maybe the problem is the weak flow coming out of the plug I removed, indicating that a cooling water problem still exists.
Rick

[lloyd]

I don’t know what the actual temp should be on the HD25, but I do know they run hotter than their larger brother’s like TD’s and TN’s. You can hold your finger on the head of a TD while it’s running, but not so on the smaller HD25. As long as it is pumping out hot water spray with the exhaust instead of steam, you should be OK.
If you need new leather primer seals and instructions for your HD25, as you probably will, you can contact me directly at: lautharr@sbcglobal.net More good info at: pochefamily.org/outboard

[Rick Robbins]

Well that’s good to know about the primer seals as it’s not very effective right now. Where would I see the water spray coming from? As I stated earlier, removing that plg under the head just shows a weak flow and not a good looking adequate flow. Is there someplace else I should be checking to see if it’s an OK water flow?
Unless I can adequately resolve this cooling question, I’ll probably put it on hold for now.
Rick

• This reply was modified 5 years, 2 months ago by Rick Robbins.

[frankr]

It’s been forty years since I’ve run a HD, but doesn’t it have exhaust relief holes about half way down? Water should spray out those (if it does have ’em). One thing about a HD, if it overheats, the fuel will boil in the carburetor and it won’t run worth a hoot.

A common HD cooling problem is the water tube enters the pump via a chunk of rubber. Those things often moosh over at the end of the tube, restricting the flow. Just carve it away if it does.

[Rick Robbins]

I’ll have to look at that rubber again. I did try to clean it up some when I had the pump apart, but maybe I can clean it up some more. In any case, I’ll try squirting water up that tubing and see if it comes out somewhere. Took a look for holes on the back of the leg but saw none. I suppose it comes out the exhaust port under the cavitation plate, but that being underwater when operating eliminates observing water flow there.
Thanks, Rick

[frankr]

I’m thinking the relief holes are in the round tube just below the swivel.

[Rick Robbins]

You’re right!! I just looked for them and found them where you had them shown. I’ll have to give it another try this weekend to check for water output. If that’s spitting water, I guess I’ll have to assume the higher block temps are normal. I’ll repost my results when I get to try it. It’s pretty cold here right now so it may be awhile.
Thanks for the info,
Rick

[dave-bernard]

those heads MAT NOT have water passages in the design.

[Rick Robbins]

There are water passages as I removed the head and looked at them for blockage. I haven’t run it again to look at the exhaust holes, but was thinking last night that I should also check the area where the cooling water leaves the block and enters the exhaust flow. Just to make sure there’s no blockage there. I’ll see if I can locate that, possibly remove the leg to find where it’s located.

[crosbyman]

have you tried air pressure or soft wire via accessible passages

was this a salt water motor ? any possibility of deposits, crud calcium is the water circuit??

Joining AOMCI has priviledges 🙂

• This reply was modified 5 years, 2 months ago by crosbyman.

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