Trojan Boat Forum

Hi Folks,

Rob Dryden in Australia here. I have an early 80's 10 meter international with 2 Crusader 454 engines, the boat is great.
I have developed a problem on the Port engine, she overheats if I increase or decrease speed fairly quickly. If I do a slow ramp of speed the problem is not evident? I am wondering if it is either the Thermostat on the freshwater circuit or a restriction (fouling) in the FW/SW Heat Exchanger.

Any advice before I start pulling bits off will be gratefully received.

Cheers

Rob

Could possibly be a broken off bit of the water pump impeller blocking the flow. When you increase speed rapidly it could force the broken part to block the flow but when you increase speed gradually there is not enough force to move the broken impleller to block the flow. Just a guess.

Impellers and/or thermostats are easy take a look at and cheaper to replace. Take those options first.

Good replies. Also, don't overlook the intake grates, seacocks or strainers if you have them.

Any restriction in the supply may cause an over heating condition. Water flow upon demand on a restricted supply will be noticeable. But as the demand is applied gradually, it may not occur. I had a starboard seacock which over time, had accumulated barnicle crustation enough to narrow the opening to about 1/8"!!

How about checking the sidewall stiffness of your cooling hoses. It may be possible that they are collapsing under the heavy throttle? Had it happen before myself.

Thanks everyone for your practical and common sense suggestions. I have a spare thermostat & SW Pump impellor, so they will be my first port of call. The inlet system (sea cock, strainers etc) are all OK as I have just come off the slip and checked them myself. Will check my hoses and if necessary remove heat exchanger end covers after.

Cheers & thanks,

Rob

Rob,
If the raw water impeller has failed, make sure you get all the pieces of the impeller out. Check the trans oil cooler and oil cooler for broken pieces. They can restrict the water flow.

I opened up the grates on the intake on the bottom of the boat and mine stopped overheating.

All great suggestions so far. The only thing I would add is check your vaccum side hose, the one from the seacock to the impeller intake. It should have spiral metal inside preventing it from collapsing under a pulling (vaccum) load. If your's doesn't have it, you'd be wise to replace it with one that is reinforced with this spiral metal 'spring.'