Mariner 60hp - replace thermostat in powerhead - how to remove?

Hi there.. my t-stat wire broke off and i tried to re-solder it without luck.. I have a great US made thread die set - could I drill out the old one? trying to not damage head but if i have to ill re-tap and get a similar stat and cut a new thread.

are these stats actually successful at avoiding heat issues? ie is it worth fixing or is there a better solution?

I think you mean the temperature sensor? There are a couple types that were used, I can't recall what year your motor is. Some of the sensors threaded into the back of the cylinder block water jacket cover where there's a tapped hole (1/8" N.P.T.).

I see these sensors aren't extremely expensive (like under $30 for a Sierra Marine replacement).

There's another type that's very small and fragile, and it screws into the machined end of the top cylinder. Those are hard to repair and very expensive (like $360.75 here).

Either one could be drilled out and re-tapped but you'd need to be sure of the thread type (tapered pipe thread or standard thread). I'm thinking the temperature switch that threads into the block has straight threads.

Quite frankly, that switch goes off a 260 degrees and by the time you get an alarm, the engine is probably toast anyway.

IMHO a better indication of cooling system health is a water pressure gauge. You can monitor it to see what the normal operating pressures are, and this will also tell you over time when the impeller is degraded.

If you happen to have the inexpensive sensor/switch that screws into the water jacket cover, that's an easy one to replace. You might even be able to drill it for an EZ-out-type tool. Or just drill all the way out and re-tap, pretty sure that one's NPT.

You could install an aftermarket water pressure gauge, by tapping into the telltale line which is the same pressure as the block. Or, if you have threads at the water jacket cover (or an undrilled boss), there.

An aftermarket temperature gauge might be a good addition to a water pressure sender, you'd have a temp gauge on the dash along with pressure readings, two valuable pieces of info when you're operating.

A pic of the sensor and the back of the block in general will help us figure out which one you have, and to explore the options for additional monitoring eqpt.

Cheers..........ed

gr8 ed tx a mil - ill snap a pic and get it back here.. its a small hex brass nut right next to cyl 1 plug, fyi mines a 1990 60hp 3 cyl..

i did look up some parts.. ill look into the tell tale pressure, but surely its really low? would a regular water press gauge handle the low pressure?

also - can i use almost any regulator on my motor? getting 16v at idle!

I believe 16 volts is high, Time for a new rectifier/regulator,question#1 what caused it to go bad, excessive engine heat? you mentioned telltale weak, it's a sign of weak water pump. Some regulators are cooled by the water jacket on the head.Can hand be placed on head? Can hand be placed in telltale stream without getting burned? Try these tests. PUll thermostats and check suspended in pot of hot water to see if they open,1/4 inch maybe less. If okay pull lower unit and replace entire pump assembly not just impeller,seal it also.

Here's a recent discussion on voltage regulators:

http://www.marineengine.com/boat-forum/showthread.php?432842-Over-charging&p=545412#post545412

See my comments, I posted some links to various regulator/rectifier assy's that would work on your motor as well.

There are water pressure gauges that have a range compatible with your motor (0-15 psi typically). Usually these don't pump much more than 10-12 psi at full throttle, quite a bit less at idle.

So it sounds like you have the very $$$ sensor, an aftermarket kit with temp gauge and sensor would be way cheaper if you can fit the sensor in the rear cover. Otherwise I suppose you might be able to install it in the telltale line, if you can find a "tee" that would install in the line, and have the correct threads for a sensor.

Here's a temperature gauge at this site, you'd have to order the sensor/sender separately:

http://www.marineengine.com/products/accessory.php?in=1763269

Here's a water pressure gauge kit: http://www.marineengine.com/products/accessory.php?in=1763215 Although you really only need a 0-15 psi gauge; I don't see any of them at this site. Note you'll find the compatible temp gauge if you scroll down the page.

If you have a weak telltale, be sure it's not plugged. Blow compressed air up the tube and see if that helps. If it's been a while since impeller replacement, probably a good idea to do so.

If your motor does have a regular thermostat (and I'd have to look it up to be sure), the block will run fairly warm but the exhaust manifold cover should stay cool to lukewarm. If the manifold cover is too hot to touch, it's way too hot.

HTH..........ed