How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

Problem has been persistent overheating about 4000 RPMs. Lower RPMs it runs all day, hit 4000 and the alarm goes off. Pulled lower unit tonight, hoping to find something obvious. Impeller is nice and flexible, with no obvious signs of wear. ( it was replaced by a local boat shop upon my buying it) Is it possible they installed it the wrong way? Looking straight down at the impeller housing/ drive shaft, which way should it be rotating? Anything else I could be overlooking here? Really appreciate any help here, this problem has really sucked the fun out of buying this boat Thanks, Larry

Re: How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

Hi Larry,

The impellor will rotate in the same direction as the flywheel. Which is probably clockwise. You can tell by looking for the timing marks on the side of the flywheel. If the advance marks are to the left of top dead centre (0 degrees) the motor turns clockwise looking down on top of the motor. The veins on the impellor will turn themselves around once the motor has started but it is best to fit then the correct way as the veins can be damaged when they flip especially if the impellor is not new. I usually replace the impellor if it is older than a year. It’s cheap insurance and you have gone to the trouble of removing the lower unit anyhow.

Make sure you have the correct impellor for the motor.

A couple of things you can check.

Look for wear or pitting inside the water pump housing and on the wear plate that the housing fit on top of.

There is a seal on the end of the water tube that leads up to the engine. This seal fits into the outlet hole on the water pump. Check the condition of the seal. I’m not sure if this is relevant to Suzuki motors but on older Mercury motors this seal is only a force fit to the water tube. It could be forced up the tube when refitting the lower unit if the lower unit is not kept in line with the motor. This causes a poor seal. I use to make sure the seal was pulled down the tube slightly before fitting the lower unit back and making sure I kept the lower unit inline when fitting it. This method made sure the water pump fitted tightly to the seal.

Have you checked the thermostat? It is on the top of the head of the motor. Take it out and see if it is clogged. Take care when loosening the bolts. If they have not been removed for some time they can corrode and snap off. If you still have the lower unit off you could back flush the system with a hose. You can also check to see if the thermostat is opening when it is heated. This can be done by placing the thermostat into a pot of water on the stove. Your manual will tell you what temperature it should open at. Use a thermometer to check this. You may need to replace the thermostat housing gasket as they often break when removing the thermostat housing cover.

Good Luck

TwoFish

Re: How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

Wow! What a detailed reply, thank you for so much info! I cranked the motor to confirm rotation, and it does turn clockwise. Looking down at the impeller housing and, visualizing rotation as I flipped it over, the impeller was installed correctly. Was hoping it could have been installed wrong, seems most are saying it will flip itself around if it was screwed up initially.
I pulled and checked t-stat a while back hoping this was the problem, opened up quickly and fully while on the stove, then I ran boat without t-stat, with identical results regarding RPMs and alarms.
Impeller and housing seem in fine shape, however wear plate has a little gouging around the perimeter, maybe enough to cause overheating?
I will check the housing outlet to water intake fitting, maybe an O-ring has slipped, causing leakage and over heating.
Thanks for the ideas and suggestions, will continue to work my way through this problem, Larry

Re: How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

You mention grooves in wear plate...most folks replace the entire water pump Kit, which includes wear plate, impeller, etc....Kit only costs a few bucks$ more than just the impeller alone.....Check your Pressure Control Valve also...it's a key part of your cooling system and could be sticking open or closed....

Re: How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

OMG!! Pressure control valve!! Haven't heard of this one yet, a clogged/ malfunctioning valve could cause problems, please tell me more!!
Larry

Re: How to verify correct rotation of impeller/ drive shaft DT 85 Suzuki

OMG!! Pressure control valve!! Haven't heard of this one yet, a clogged/ malfunctioning valve could cause these problems, please tell me more!!
Larry