1987 V4 Crossflows - Thermostats

[Solittle]

I just got back from the kitchen after checking the thermostats that I replaced from my twin V4s. One engine had stainless t-stats with a pop-up design. One of them was frozen. The other engine had brass t-stats with a pop-down design. One of them would fully open and the other only part way. This is the first time I have checked t-stats in hot water on the stove afte replacing them. Neat to learn how stuff works. That leads to a question.

When I first got this rig one of the engines was frozen and needed to be rebuilt. This was considered in the pricing negotiations. I had a professional marine mechanic rebuild this engine. One of the recommendations he made was to install new t-stats but to "cut the nibs" thus removing the guts of the t-stat but saving the diameter of the hole for the water flow. Granted that the full performance of the t-stat would be lost during warm-up but when at operating temp the water flow and hence the temperature should be the same as if the de-nibbing were not done.

While that may not be a question I would like some comments.

 

[funpilot]

Re: 1987 V4 Crossflows - Thermostats

So, basically your mechanic is negating the T-stat function, but guaranteeing that the device will never stick 'closed'. I don't know about salt water operation, but here in the great North, I've never had a T-stat fail closed. Quick warm up is good for the cylinder to ring clearance and wear, and for that you need a functioning T-stat. If you really want to be paranoid (not you specifically, but more of the 'queen's' you) you could simply check the T-stats every other year or so, clean them up and reinstall.

I say, put them in and let them function the way OMC meant them to.

fp

 

[rodbolt]

Re: 1987 V4 Crossflows - Thermostats

only crossflow T-stat mods I would make are to cut tiny notches in the poppets on the new stainless ones and to open up the water bypass hole in the holder to 1/8".
with the poppet missing it will run cold and usually idle poor at low speeds.
when OMC first came out with the self flusing t-stat it was brass and had a vent in the poppet to allow the hot water from the head into the T-stat housing. the newer style stainless ones dont have this vent and it occasionally leads to an overheat the first time its run when cold.
the solution was to vent the poppet and enlarge the water bypass hole slightly.
but its common to see a crossflow with stainless non vented t-stats to set the hot horn and the t-stat housing is ice cold.