Saving Old Seagulls

I am a rookie owner of these awesome motors. My in-laws gave me a 1972 long shaft and said I could "tinker" with it and try to get it running. Well I did and she runs great. Apparently my Seagull is an oddity here in the U.S., people are stopping me asking what it is and love the retro look of it. I am experiencing one problem with it though, she circulates water fine when the prop is not engaged, but when it is engaged it is not wanting to circulate, causing the motor to run very hot. I can idle her down and disengage the prop til she cools off, but this makes for long trips. Any suggestions?

Welcome, it would be helpful to know what model you have, as they are not all the same, If you run it in a water tank or butt they sometimes struggle to bump, especially with the prop churning up water, the water pump works when the motor is running, no matter if its in or out of gear,
A water jacket clean out maybe be the next step.

Thanks Keith, here is the id numbers from mine...WSPCL737HH5. The circulation issue was actually on the water, not in a tub. When you say cleaning the water jacket, what exactly are you meaning? Thank you again.

First thing to try is a back flush ie put a hose nozzle into the outlet and give it a good flush, keep an eye out to see what crud comes out the bottom. Second thing you can do is soak the water jacked with a descaling solution (used to clean clothes iron) by placing motor upside down and filling through outlet and leaving for 24hrs and then backflush. This might need to be done a few times. Third thing is try is to remove the head ie the bit that says do not remove and then clean out the exposed water jackets. Beware that these head bolts have a tendency to shear off causing stress. I usually give them a quarter of a turn and leave overnight. If they are seized the untwisting torque keeps working to undo them. Don't get a spanner and hit with a hammer until free... they will break. WD40 and heat helps. Clean your points and adjust. If points gap is too small the motor will run advanced creating heat. If you run a richer mixture ie more oil the motor will run cooler. Does the water turn to steam before drying up? Sounds as though it is just clogged up a bit.

While running the exhaust tube should be submerged 1-2inches.

Thank you everyone for the tips and advice. I actually flushed with vinegar and WD-40 rust breaker, turned upside down and flushed with water, and she is pumping fine now.

Hmm that sounds that an inspection in the waterways is essential. You have loose flakes of rust/deposits inside. With use and time that will create a solid crud that would be really nasty to remove it.
Just had it in your mind and after a year or so you can visit the internals.