hot air engine bay

[floater212]

I have a rinker captiva 212 2005 350 mpi. Here's a weird problem I had the sun deck cover fixed from a seam split when it was repaired the shop pulled the edges down it puffed out the sides so the fit is tight around the opening. So tight there is no or very little air going into engine compartment. Now it's real hot in there. Anybody have this problem? I have a side walk-in from swim platform the side which is also the engine compartment has a cubbie where I store docking lines. I'm putting in a 4" vent which I'll add vent hose to a blowers to force more air in. I think that will work out great. It will get more air with or without blowers on like an air scoop. I'll let you know in the spring.

 

[Fun Times]

Re: hot air engine bay

Yes unfortunately from time to time the engine compartments will get tightly sealed up to help lower the engine noise thus creating high engine compartment temperatures. Having the proper amount of air ventilation is vital in order to help keep the recommended maximum air temperature allowed from reaching the 176 degree point measured at the flame arrestor. Increasing the engine compartment ventilation system is suggested to be designed to help move the hot air out of the engine compartment during heat soak along with an adequate air intake system.

Good luck.

 

[04fxdwgi]

Re: hot air engine bay

I just leave the bilge blowers (I have 2 blowers installed) running on mine all the time when engine is running. Keeps plenty of air flowing in there.

 

[thumpar]

Re: hot air engine bay

Mine seals pretty tight and get hot. What I started to do is run the blower at low speeds and for a while after stopping. The boat has some built in vents toward the front that look decorative but lead to the engine bay. Those supply air while at cruising speeds.

 

[floater212]

Re: hot air engine bay

the only vents are at the back end tucked under the sun pad and there are NO vents to let air in, just out. that's why I'm making a intake blower to add more moving air. I'm sure when it's all put together the 4 small 3" vents under the pad will feel like a hair dryer on full! so now I'm thinking of open 2 of the 3" vents up to a 4" vent and adding some metal under pad for heat deflection. over kill? maybe but right now I have way TOO much time to think on this.

 

[HT32BSX115]

Re: hot air engine bay

I'm putting in a 4" vent which I'll add vent hose to a blowers to force more air in. I think that will work out great. It will get more air with or without blowers on like an air scoop. I'll let you know in the spring.

You already have a bilge blower that "sucks" air OUT. I had a similar (perceived) "problem" so I just added an additional bilge blower.

The inline blade-type fans work well. If you want MORE airflow, get a "squirrel-cage" type blower.

blower - iboats Expect to spend some money on a good continuous-duty type blower too!

Don't install it to "blow" air IN (you'll be smelling engine blowby gases etc in the cabin area.....) ............. connect it to a existing hose and deck vent to suck the engine compartment air OUT and overboard!



Regards,


Rick

 

[Barraspalding]

Re: hot air engine bay

Cooler the engine bay the better, as this is where the engine is drawing its air from - cooler air equals more power.

Has anyone set up a sealed air box to isolate the hot engine bay air from the carb/EFI air intake?

Btw the standard blower on my searay 180 seems to blow out very well, but not taken notice of the temp in the engine bay. Should it be regularly checked whilst underway?

 

[floater212]

Re: hot air engine bay

my boat is a open bow 21' runabout so there is no enclosed cabin and also the exhaust vents are only out the back end by swim platform, under the sunpad, no other way the flow could go. I was going to install it to blow in from back of a side cubbie to the front of engine so the flow would go out back, but if I plumb the vent the same but put fan on the out bound air vent in the back that should still help cooler air in and hot air out..... right? this only started after the sunpad had 2 seams re-sewn and the sides were pulled so tight to attach it back on that the squared off sides are now 1/2 round and it seals very tight to the point of 2 hands on the strap to open engine cover when it used to take just 1 hand.

 

[HT32BSX115]

Re: hot air engine bay

if I plumb the vent the same but put fan on the out bound air vent in the back that should still help cooler air in and hot air out..... right?

That's how you want to do it.

You should already have a bilge blower connected like that. Adding another identical one operating the same will double the air flow into and out of the engine compartment.

 

[floater212]

Re: hot air engine bay

my main concern is there is little or no air flow going in since the sun pad got redone, tighter seal, and the 4 3" hole of which 1 is the bilge fan, isn't flowing air in because of location. the 3" vents are side by side just touching each other, so if air could get in 1 vent it would go directly to the other vents so the only air flow would be vent to vent and none would fill and move through the engine bay itself, so all I'm looking for is an easy way to up the flow, fresh air in hot air out.... as it is now fresh air just isn't enough to even come out the vents because of the location side by side vents behind the engine and under sun pad where the air isn't being pulled out , negative pressure, and not like a truck, air comes in in front and goes out behind the motor... air flow.

 

[Walt T]

Re: hot air engine bay

Barraspalding asks a good question about checking air temps in the engine box. I did that once on a fairly new at the time Four Winns 205 Sundowner with a 350. We had been talking about engine bay temperatures and vapor lock, so as curious mechanics (drunken bums) will do, We ran it on Powell on a hot summer day with the blower going and without it. As far as we could determine the engine area was within a few degrees no matter what. On my boat ('88 Hydroswift 2200, V-8 Chevy) it was the same (little difference) however the Hydroswift air temp was a good 30 degrees cooler than the Four Winns. I am sure that is because the Four Winns had a much tighter cushion and fiberglass hatch situation and the engine sat relatively lower in relation to the floor than the Hydroswift which was just a fabricated wood engine cover and seat cushions with a lot of room behind it all for air to freely move. The Four Winns was quite a bit quieter too because of its design. The Hydroswift was also considerably faster but that's probably due to hull differences mostly. I'd be curious to see what other boats temperatures are in there with blower running or not, in cool weather and cold weather too. Fact is, cool air is denser than hot air and therefore more power is available. That's why we see 'snorkels' on automotive and truck intakes near the front grills.

 

[Bondo]

Re: hot air engine bay

Ayuh,.... While I donno yer boat, very few rely on air from the motor box,...

Most hulls, the in-comin' air comes down through the gunnels to the motor box, 'n is exhausted by the blower, 'n aft facin' vents,...

 

[floater212]

Re: hot air engine bay

I think I have another solution... I have the rear bench that wraps around one side and in the middle back has a spot for a cooler, it's a double wall and it's directly over the fuel tank access; if I put a 4" screened vent in the front of the cooler box, air would pass through the walls over the tank and directly into motor bay.... no power needed... ram air effect! what do you guys think?

 

[thumpar]

Re: hot air engine bay

I think you would get fumes in the boat when stopped. This is a picture I had handy of my boat.


The crown is actually an intake for the blower. The silver oval is a vent that feeds back to the engine bay. It doesn't have a blower on it but gets air when running at speed.

 

[floater212]

Re: hot air engine bay

that's what I'm talking about.... front vent aren't used much any more, that would solve the intake problem... thanks!

 

[aerobat]

Re: hot air engine bay

i have two side vents with a blower attached to the starboard side - it does not suck but forces the air in . that keeps the engine compartment really cool - with blower off it indeed also on my boat gets hot.