2002 5.7 Bravo 3 steam in exhaust at high RPMs

[dollar7499]

1998 block 5.7 Bravo 3 built to spec of # 4312025PS (the # Crownline gave me from the hull #)

The P.O. replaced a cracked 2003 engine with a 1984 long block and sold it to me. I yanked the 84 and installed a 1998 long block, 4 bbl marine intake, marine quadrajet, and the box of correct model parts I received with the boat. I finished installation and it fired up and purred the first try. Set base timing, and then after a good warmup decided to give it some RPMs... when I got to 3200 RPMs I saw clouds of steam coming out of the prop. I immediately shut it down and checked the oil - everything was good.

It has the 3 point drain raw water cooling with only water inputs on the manifolds, none on 6" extensions or elbows. Cleaned up bravoitis during rebuild and flow looks good, lots of water coming out below transom but not much coming out prop. My elbows were getting pretty warm though, is there a chance too low of flow through elbows was causing steam? I flow checked all exhaust components during rebuild, so where is this steam coming from?

It's in a 2003 Crownline 262 CR Thanks!

 

[Scott Danforth]

Water + exhaust = steam. most likely your seeing water vapor

you were running at 3200 RPM on muffs? dont do that, not enough water flowing thru muffs to go above 2000

how warm is pretty warm? the elbows will be about 180 or so, and if your running on muffs, one will be warmer than the other if your boat is not sitting perfectly level.

 

[dollar7499]

That is really good to hear, that it might just be muff related! It was just highly uncomfortable to rest hands on the elbows, like if the black painted elbows were sitting out in the full summer sun. Not burn inducing hot.

 

[alldodge]

Agree, steam no biggie right now, but running it up to 3200 you might have damaged the impeller. Keep close eye on the temp gauge when your running around for the first few trips

 

[dollar7499]

Thanks for the replies! Along that same line about watching my temp gauge- I have a coolant temp sensor on the t-stat housing and one on the intake. My schematics don't really show me which to hook the tan wire to... I have it on the t-stat housing now.

 

[Scott Danforth]

tan wire is the gauge. goes to the sender in the intake/t-stat

 

[alldodge]

Thanks for the replies! Along that same line about watching my temp gauge- I have a coolant temp sensor on the t-stat housing and one on the intake. My schematics don't really show me which to hook the tan wire to... I have it on the t-stat housing now.

Agree with Scott and will add, one of them is a sensor and the other should be a switch.

If you connect the Tan wire to the one a the thermostat housing and it never moves it might be a switch. If it doesn't move connect it to the other one and see if it causes the gauge to moved when warmed up.

The switch is for the overheat alarm and wire should be Tan/Blue

 

[pullin]

I realize this isn't a technical answer, but here's a video of my Bravo 3 while getting up to plane. Mechanic says this is a normal amount of steam and not to worry. (Advance to 6:50 to avoid the boring parts)

 

[alldodge]

Looks like you have either an exhaust tube or your exhaust boot is torn/not there. Assuming the water is cold, and if air is also cool this would not be an issue of concern, so long as the motor is not overheating

 

[Bondo]

Mechanic says this is a normal amount of steam and not to worry.

Ayuh,..... Yer Mechanic is Right,.....

The function of the exhaust risers is to dump 140*/ 160* water into the exhaust stream which is nearin' 800*, so steam is a fact of life,....

The local outside Temps, 'n Humidity determine how much of the steam ya see,..... or don't see,....

 

[dollar7499]

You guys were right as usual about muffs just not being enough water... I took it out on the lake and it ran much cooler. So cool, I have to get a choke for my carb I didn't think I would need.

 

[Lou C]

It's a good idea to keep an IR temp gun on your boat. This way you can check the temps of the elbows/risers at idle and after coming off plane to see what your normal temps are. When I still had the old OMC one piece V6 exhaust I would get readings of about 90-100 at ldle and the most it would go to was about 135 after coming off plane, but they would cool back down to about 115 pretty fast. When I get the boat in the water with the new Volvo style center riser system I'll check to see if there are any differences. Running it on the water hose the manifolds run cool like about 70* or so and the elbows, about 85-90, one side being a bit higher as is expected. The cooling ports are much larger in the center riser style than in the old one piece units so I'd expect them to run a bit cooler, we'll see.