Motor trouble for my scratch built 85in 1:2.75 scale Chris Craft

I need help from guys who know about big motors. I scratch built a 85inch x 29Inch. 115 lb scale model of a 1939 Chris Craft barrel back. I wish I knew how to share pictures on this forum but trust me it?s beautiful. Built it for my son to ride in.

Now I know I this is a rare boat most will know nothing about but bear with me.

My motor keeps overheating and I think I?ve damaged it and I want to replace it with a motor that can swing a large enough prop to plane with my son in the boat. Let me explain my set up:

TP 5680 (56mm x 118mm) brushless motor (rated to 300 amps and 15000 peak watts), 650KV, an MGM 40063 400 amp controller, running 4s 6p, and a 3 blade 4 inch prop with a 1.3 pitch. It?s actually a model tug prop from harbor models. Water pumps run continuously for cooling and dump into the exhaust. Both pumps are still working fine.

When I first started testing I ran a 3.5inch 3 blade. Everything basically ran at 5 degrees Over water temp. 75 to 80 F. It would barely plane with a kid in it so I stepped up to the 4in. The esc hovers at 95-105 F. Capacitors at 115. The motor however is at 120-130 on the jacket and 140-180 F on the front of the can. I?ve seen the motor wires hit 190. After 3 mins of running. So I backed it down to the 3.5in after trying to see if driving behaviors would allow it to run cooler. So I ordered a 3.75in prop for a compromise.

But now when I went back to 3.5in I still was hitting 115-120 on the jacket and 130-150 on the can. Did I ruin the motor? I need a 56mm motor that can handle the amps and swing a 3.75? prop. Any thoughts? Lower KV. Different brand?

First, terminology. How many volts are you running to the motor? 4S (14.8 volts) is a bit low for that size motor. What capacity is each pack, 6P (6 packs) is a lot of capacity.

What speed did the boat achieve with your son in the boat? What speed do you want? I am assuming that the boat with boy will weigh well over 50 pounds, and IMO that is a lot for a single hobby-grade motor with a submerged drive. TP is a good brand and they make larger motors with lower Kv values - but you are outside the experience zone of most on this site. Hopefully another member with actual experience will step up.

It sounds like a great project and I hope you get it to work for you. Here is how to post pictures, it really isn?t too difficult.

https://forums.offshoreelectrics.com...highlight=Post



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[QUOTE=Fluid;747744]First, terminology. How many volts are you running to the motor? 4S (14.8 volts) is a bit low for that size motor. What capacity is each pack, 6P (6 packs) is a lot of capacity.

What speed did the boat achieve with your son in the boat? What speed do you want? I am assuming that the boat with boy will weigh well over 50 pounds, and IMO that is a lot for a single hobby-grade motor with a submerged drive. TP is a good brand and they make larger motors with lower Kv values - but you are outside the experience zone of most on this site. Hopefully another member with actual experience will step up.

It sounds like a great project and I hope you get it to work for you. Here is how to post pictures, it really isn?t too difficult.

https://forums.offshoreelectrics.com...highlight=Post



.[/QUOTE

4s6p with 5000mah packs. Gives me about 30 mins run time. I was afraid of going higher on the voltage with such a large prop. My focus was low kv, lower rpm and a prop with enough surface area to push the large of a hull.

Without the kid and with a 3.5 in prop it achieves 19 mph. My son weighs 35 lbs So a total of about 150lbs. with him in it it does about 10 and struggles to plane. With the 4 in prop it?s fine

There was no ?manage attachments? option for me

Email me your photos and I will post them. I PM'd you my address