Please Fill Me in on Mercruiser Seawater Cooling Systems
05-12-2007, 04:46 PM
#1
Registered
Thread Starter
Please Fill Me in on Mercruiser Seawater Cooling Systems
I admit I don't know much about the cooling system on Mercruiser sterndrive engines. I grew up with inboards, V-drives and jets. I keep hearing about overly high water pressures in the cooling system. I have a few questions.
1) Isn't there a seawater pump in a Bravo drive?
2) Why is there also a seawater pump on the engine? Is it required for when the boat is stopped or going very slowly?
3) What's causing these high water pressures, just the ram force on the drive water inlet?
Michael
1) Isn't there a seawater pump in a Bravo drive?
2) Why is there also a seawater pump on the engine? Is it required for when the boat is stopped or going very slowly?
3) What's causing these high water pressures, just the ram force on the drive water inlet?
Michael
05-12-2007, 05:19 PM
#2
Registered
Join Date: Aug 2006
Location: Colonial Beach VA
Posts: 629
Likes: 0
Received 0 Likes
on
0 Posts
As far as i know the only pump in a bravo application is on the engine , the drive is just a water pick-up
but at idle (650-750 rpm) it supplies e-nuff water to maintain cooling , the pick-ups in a stock bravo drive are on the sides of the drive so no extra pressure is created at high speed , just the pump running at 5000 rpm instead of 500
the pressure of the water would have to do with how much restriction there is in the system (ie , thru transom exhaust vs thru hub , water bypass vs engine circulating pump , dry exhaust vs wet exhaust and so on)
hope this answers your questions correctly
still consider myself a novice , but my boat does have the bravo sterndrive
but at idle (650-750 rpm) it supplies e-nuff water to maintain cooling , the pick-ups in a stock bravo drive are on the sides of the drive so no extra pressure is created at high speed , just the pump running at 5000 rpm instead of 500
the pressure of the water would have to do with how much restriction there is in the system (ie , thru transom exhaust vs thru hub , water bypass vs engine circulating pump , dry exhaust vs wet exhaust and so on)
hope this answers your questions correctly
still consider myself a novice , but my boat does have the bravo sterndrive
05-12-2007, 08:41 PM
#3
Registered
Join Date: Oct 2004
Location: Upper Chesapeake Bay
Posts: 319
Likes: 0
Received 0 Likes
on
0 Posts
On the Bravo drive the vertical shaft does not turn while in neutral because the transmission is in the top of the drive. This is why they have a sea water pump mounted on the motor.
05-12-2007, 09:26 PM
#4
Registered
Join Date: Feb 2005
Location: long island, newyork
Posts: 2,551
Likes: 0
Received 2 Likes
on
2 Posts
both above posts are correct to an extent. the drive is shifted in thee upper. and the drive is a pick up.
however the water at the speeds alot of the boaters here run at does in fact have a ramming efect on the pickups. especially when you install a " shortie drive" or " shortie lower". the pickups on these lowers are on the under side of the bullet which in turn rams the water in creating excesively high water pressure. you must then relieve the water system of said excess v.i.a water dumps or pop off/ blow off valves, etc,,,.
however the water at the speeds alot of the boaters here run at does in fact have a ramming efect on the pickups. especially when you install a " shortie drive" or " shortie lower". the pickups on these lowers are on the under side of the bullet which in turn rams the water in creating excesively high water pressure. you must then relieve the water system of said excess v.i.a water dumps or pop off/ blow off valves, etc,,,.
Charter Member
Thread
Thread Starter
Forum
Replies
Last Post
Michael1
Drives and Lower Units
1
10-25-2007 05:35 AM
