MikeyFIN

+1
As a sidenote;
Well try to heat/boil saltwater and look at the sides of the kettle after that.. you donīt need to be much of a genius to figure out why raw water cooled engines has low T-stats...

Rookie17

Maybe apollard and I run in the same circles

Since apparently today I'm throwing my opinions out there, I don't think controlling detonation with lower water temps is the greatest idea either.

Shouldn't detonation be controlled by effective ignition timing / air-fuel ratio (AFR) and compression (combustion pressure)? In rarer instances perhaps, also air intake temp and fuel burn rate (octane) too of course.

If a lower engine temp is needed to control detonation, seems to me it has too much or not enough of one of the above.

Ok, I'll sneak outta here now in case I just started a load of trouble. Just my opinion guys, don't let me pizz any of you off

kreed

iTrader: (2)

ALL helpful info, so now, will running an engine at 150 water temp and a 180 to 210 oil temp as opposed to having no t-stat change carb jetting? Another words, will an engine run rich or lean depending on engine temp? Depends on air temp of coarse, but will engine temp affect it?

apollard

Maybe - Mooresville is full of us know-it-alls

FWIW, I'm with you on the detonation issue, but have zero experience with blown motors, and don't know any builders of blown moters, so it might be different. Engines don't always appear logical, at least until we figure them out.

apollard

Yes, it should - more of the fuel will be in vapor form and therefore burned. Vapor burns, liquid gas drops do not (or at least burn poorly). If jetted to run at say 100F, and you increase temp to 160F, you should go rich. Whether it would be enough to cause an issue depends on how bad your fuel distribution was at the lower temp. I had to drop one jet size on my secondaries when I started running 170F - but my jetting was slightly fat before (but not a full jet IMO)

MILD THUNDER

iTrader: (3)

Theres alot of theories here. Some good ones. However, sometimes theories, do not give real world results.

The beauty of this day and age, with the internet, is that one can save himself lots of time and aggravation, by not trying to re-invent the wheel here. It has been done, by people like merc, and many other successful offshore engine builders.

Controlling detonation can be done alot of ways. Its all about finding that happy median. Every application is different. The key to keeping a marine engine alive, is not only controlling detonation under most circumstances, but yet almost all circumstances. You want a good margin of safety, whether it be lower compression, less timing, aluminum heads, rich jetting, cooler water temps, etc. Car guys can get away with being close to that edge sometimes. Us however, put tremendous loads on our engines, get crappy gas at marina's, etc. One hard run while thinking you got 93 octane, when you really got 89-90, can cost you your engine.

One guy stated that he feels controlling detonation by means of water temp doesnt sound right to him. To me, trying to make HP by increasing water temps, doesnt sound right to me. If horsepower is what you seek, theres better ways to do it.

Bottom line, my thoughts are to stick with what works. Think about this, you got some stainless headers. You are out running hard, t-stat's wide open, sending 190-200* water to your headers. You shut it down to get gas. Your headers have 200* water cooking in them. Now, you fire it back up, and t-stats are closed, trying to build engine heat. In the meantime you are bypassing and sending 65* cold lakewater into your piping hot headers. That cant be good. You can put your hand on my headers after a hard run. 200* water temps, and those headers are gonna be HOT, along with the rest of the block.

Rookie17

For me personally, its about engine health and longevity and not horsepower being the reason I'd like to see my engines run warmer.

I think someone earlier brought up a good point though. If Merc lowered the engine water temp by using 140 thermostats due to the salt remnants for those running in brackish or ocean water, that may explain why Merc wanted the water temp down.

Perhaps my little experiment with warmer water temps is only relative because I only run in fresh water on Lake Norman.

The older I get, the more I find out I know less... Maybe one day I'll learn to stop trying to reinvent the wheel, but it sure can be fun. And sometimes, you even discover something new

MILD THUNDER

iTrader: (3)

The key to engine longevity in a marine performance motor, is more in the valvetrain than anything. For example, a stock 310HP 454 may go 1000 hours, before needing a top end job. Where as a 450HP 454, might go 300-350 hours before it needs a top end job. Mainly because of the larger cam, stiffer valvesprings, lifter wear, etc in the higher power engine. The bottom ends, pistons, rings, bearings, etc rarely wear out prematurely.

Remember the old days, before cars had all this computer stuff.....Those hot 90 degree summer days when the temp would creep up on you, pinging was always a issue, even on a low compression smog V8 with a very conservative timing advance. It was the heat retained in the cylinder heads and pistons. Therefore guys were running bigger radiators, fans, cooler thermostats, etc. Hotter the engine got, more likelyhood of pinging. Cool it down, it was good to go.

The reason you can run a little more boost in a blower motor with aluminum heads over iron heads, given the same compression, timing, and boost psi. Because the aluminum head dissapates the combustion chamber heat better than the cast iron does. Same goes for water. Cooler water flowing thru the heads, around the cylinders, will help keep them from lighting that fire when you dont want it too..

I am no engine builder by any means. Just going off information i have collected from others over the years....Great topic though...Would love to hear some of the pro's insight on this...

apollard

It would be interesting to hear what Eddie Young or Ray, or other pros had to say- always up for learning something.

kreed

iTrader: (2)

Yea, I agree, everyone has a different theory. I guess I need to figure out what works best for my combo. At the end of all this, I guess Im going with a 140 stat. Gonna start the engines, check water pressure, and then watch oil temp once the boat goes in the water. Is 25-30 Lbs water pressure pretty much max at WOT before I install pressure relief valves?