Overheating at idle

[dpr17]

1988 BFN (351 PCM) closes in on 180 at idle, but runs 160 at higher throttle. Seems like the the Tstat opens, but not sure. After reading all the posts about overheating, particularly at idle, I know I need to start with the impeller, hoses, and sea strainer. One thing that I didn't see was belts. I replaced the belts this year and noticed crumb rubber on the pulley housings rubbed from the new belts. Could this be alignment or a tension issue? Is this normal with new belts? What is the correct procedure to set for proper tension? Thanks!

[pj]

RE: Overheating at idle

take a look at your water strainer. most likely it is not screwed on tight enough and there is a small air leak. that will cause it to suck some air and get hot at idle but would flow enough water when underway to keep it cool.

[DanielC]

RE: Overheating at idle

The pulley surface where the belts go has to be smooth. If there is rust on that area, it will wear out the belts quickly.
This is a flushing adapter I made, with instructions on how to use it.
http://www.planetnautique.com/index....light=flushing
Remove the hose from the through hull fitting, and pressurize the system to look for leaks.
After about 1000 hours, I have had to replace the whole raw water pump on two different GT-40 motors, to keep the cooling good.
I do not know if the 351W in your boat uses the same raw water pump as my GT-40 does, but if your pump is the same, or similar, do this. I polish the brass plate that separates the pulley and shaft housing from the pump body, on the impeller side.
Another possibility is the ignition timing. If it is retarded at idle, it will cause the engine to run hot. Make sure the mechanical advance, and vacuum advance on the distributer are working freely, and the base timing is correct.

[uwpgrad]

RE: Overheating at idle

Gentlemen, this is my first post to this site because this topic caught my eye. I have a similar problem with my 95 Sport Nautique in that it wants to over heat when idling as well. I have had the boat now for only 3 years and I'm boater/ski since birth, but actually knowing about the inner working of a boat, I'm clueless. So this puzzles me in how I can start figuring out what is happening. I see that dpr17 talked about checking the impeller, hoses, and sea strainer. Both the impeller and hoses have replaced but I'm not sure on where the sea strainer is. Are you guys talking about just the grill on the bottom of the boat or is this something else?

[Mikeski]

RE: Overheating at idle

This issue plagued my 1995 Nautique for a whole summer. I could not get the strainer to seal. I finally bypassed the strainer, it never got dirty where I ski anyway.

Here is what happens. At an idle it just pulls air, when you take off the impeller creats enough vacuum to pull water in the motor even with air leaking into the strainer.

WATCH FOR STEAM - this is the early indicator that you are having overheating issues at any speed

[DavidF]

RE: Overheating at idle

Steam can occur around this time of year regardless of the engine temperature. Best to use the temperature guage...that is what it is for. To the orginal poster, you may have the beginnings of a problem, but 180 degrees at idle is nothing to worry about...just make sure it does not get worse. If you have not done so in awhile, go ahead and change the impellar. Do not worry about the hoses unless they are in bad visual condition. As far as the strainer, make sure the rubber o-ring is in place. If it is, remove it a smear it with silicon grease before reinstalling and tighten the bowl hand tight. Or, you can purchase a new o-ring seperately from any CC dealer or elsewhere.

[east tx skier]

This is the email I have from my local Nautique mechanic about chasing an overheat. This is the route they take when trying to nail down the issue.

Step 1 - Make sure the water pump is oriented/clocked correctly. Step 2. Make sure that your water strainer is clean (i know you know a lot of this stuff, these are just the steps I go through), the gray elbows on the water strainer are snug, and your o-ring on the water strainer is in place. Step 3, make sure your strainer grate on the bottom of the boat is not blocked. step 4 make sure both sides of the transmission cooler are free of obstruction. step 5, pull the bottom hose off of the water pump, and flush water outward, step 6, pull the top hose off of the water pump and the thermostat housing, and make sure there is no obstruction in the thermostat housing.

[DavidF]

Great advice/steps.

[Hollywood]

You still need to physically check everything for tightness yourself. Relying on the dealer to replace hoses, etc. isn't enough they can still be loose.

[dpr17]

Appreciate all the feedback. Plan to work on it tomorrow. UWPGRAD - the sea strainer is the first stop on the inbound raw water line. Clear polycarbonate screw on cup with a filter screen inside. From what we have read, the gray 90 degree fittings and the cup itself could suck air if not tight. I like east_tx_skier idea of flushing backwards from the pump out. Do I need to worry about the tranny cooler and too much water pressure in the opposite direction? Have decided that no matter what I will change the impeller (still original - 1988!) I know OMG...