Flushing a 4.2L Yamaha

Halfhitch

GreatGrady Captain
Joined
Nov 11, 2017
Messages
398
Likes
55
Points
28
Age
72
Location
SW Florida
#1
Awhile back, I repowered with the 4.2L with the dual water inlet. I miss being able to flush with muffs. I know Yamaha says the hose fitting does a good job but it doesn't give me the warm & fuzzy feeling I get from flushing on the muffs. Has anyone figured out how to do it.

 

wrxhoon

Well-Known Member
Joined
Apr 4, 2012
Messages
206
Likes
18
Points
18
Location
Sydney Australia
#7
Do you even need to tape it? I have a 250 Mercury Optimax she has the lower pick up as well, I use muffs, I don't tape the bottom pick up and she works perfect. The new boat has a 4.2 250 Yamaha so I will have the same problem as you guys.
 

Ky Grady

GreatGrady Captain
Staff member
Joined
Mar 1, 2006
Messages
743
Likes
96
Points
28
Location
Cross, SC/Berea, KY
Grady White Model
Seafarer
#9
Do you even need to tape it? I have a 250 Mercury Optimax she has the lower pick up as well, I use muffs, I don't tape the bottom pick up and she works perfect. The new boat has a 4.2 250 Yamaha so I will have the same problem as you guys.
Only reason I tape them is, I feel the loss of water out the low water pickup could starve the water pump of sufficient water flow to not damage the pump or adequately flush the motor. Just a personal thing, may be unnecessary, but I'll continue to do it. Not a big deal to tape it, flush it, then remove it.
 
Likes: Zebulon

DennisG01

GreatGrady Captain
Joined
Sep 1, 2013
Messages
2,678
Likes
93
Points
48
Location
Allentown, PA & Friendship, ME
Grady White Model
Offshore
#10
Only reason I tape them is, I feel the loss of water out the low water pickup could starve the water pump of sufficient water flow to not damage the pump or adequately flush the motor. Just a personal thing, may be unnecessary, but I'll continue to do it. Not a big deal to tape it, flush it, then remove it.
Ditto.

wrxhoon: I suppose it could change a little from one model/manufacturer to another. But keep in mind that an engine will start and run just fine without ANY water... until it doesn't run anymore. Better safe than sorry. Next time you flush, see if there's any water dripping out - if not, then you're probably just fine - but make sure you keep an eye on it the whole time and be sure to check every time.
 
Likes: Ky Grady

Halfhitch

GreatGrady Captain
Joined
Nov 11, 2017
Messages
398
Likes
55
Points
28
Age
72
Location
SW Florida
#11
I taped them off and started it up. After about 5 seconds I didn't see a pee stream so I chickened out and shut it down. KY Grady, How long does it normally take to get a pee stream on yours. I have a good water flow on the garden hose. 60 psi at the pressure tank. Do you take the screens off under the muffs?
 

Ky Grady

GreatGrady Captain
Staff member
Joined
Mar 1, 2006
Messages
743
Likes
96
Points
28
Location
Cross, SC/Berea, KY
Grady White Model
Seafarer
#12
I don't take screens off. It takes a few more seconds than what you gave it to fill the block up with water and start coming out pee hole. As long as you have water going through the muffs and have the muffs positioned correctly over the screens, you will be fine and not burning up the pump. If after a few minutes and still no pee stream, you may have a spider nest or something blocking the hole. I've gone to putting a piece of painters tape over the pee hole to keep bugs out if I'm not going to be using the boat for awhile.
 
Likes: Halfhitch

DennisG01

GreatGrady Captain
Joined
Sep 1, 2013
Messages
2,678
Likes
93
Points
48
Location
Allentown, PA & Friendship, ME
Grady White Model
Offshore
#13
Another ditto to what KY said above ;)

The important thing is not whether water is peeing, it's whether or not the water is being sucked in. When you first put your muffs on, the water is spilling out all over the place. Once you start the engine, the "spillage" becomes a lot less... even possibly none at all. That right there is the important thing - that tells you the water is being sucked in and making it's way to the engine. There are times where I bet it's easily 30 seconds before I see water coming out the telltale. And other times I see if coming out the exhaust but never the telltale (blockage, as mentioned). As long as the water is being sucked in, you're good.

FYI... water flow from the hose... GPM is more important than PSI in this case.
 

wrxhoon

Well-Known Member
Joined
Apr 4, 2012
Messages
206
Likes
18
Points
18
Location
Sydney Australia
#15
Only reason I tape them is, I feel the loss of water out the low water pickup could starve the water pump of sufficient water flow to not damage the pump or adequately flush the motor. Just a personal thing, may be unnecessary, but I'll continue to do it. Not a big deal to tape it, flush it, then remove it.

I don't know about the Yamaha until I try it. The Merc works just fine, I have a pressure gauge on the monitor and the pressure is the same with the hose as when idling in the sea.
I'm not concerned about overheating the engine, that will not happen at idle even if only a mall amount of water gets in the cooling system, keep in mind outboards run very cool temps cars run a lot hotter and overheat alarm will go off. My main concern is the water pump life if you run it dry you kill the impeller quick. I don't run it in sand or mud and change at 500 hours ( complete pump) still like new . I have to say Optimax Mercs (200 hp up) have big water pumps . I monitor water pressure, if I notice it dropping bellow normal even a little I will change impeller or even complete pump.
I think I will tape the front pick up on the Yam as well, like you say only takes a minute and no harm as long as you take the tape off when finished. On the Merc when you turn the hose on water runs from the front holes but as soon as you start it stops it seems all the water gets sucked .
 

SmokyMtnGrady

Well-Known Member
Joined
Jul 11, 2009
Messages
1,254
Likes
31
Points
48
#16
When Mid Carolina Marine started the motor for me at my repower they taped it. KY is a professional boat rigger and he tapes it. Now, you can do what ever you want, it's your motor and if Mercury doesn't need to be taped and you think your new $24k motor doesn't need taped , more power to you! Lol. I am just yanking your man. It's all good. It's a great motor and you will love it.
 

Doc Stressor

Well-Known Member
Joined
Nov 13, 2009
Messages
664
Likes
21
Points
18
Location
Homosassa, FL
#17
Yamahas are designed to be flushed when tilted up. I find that I need to tilt mine in order to get water to start flowing from the telltale. Once it starts flowing, I can tilt the engine back down and it will continue to flow.

Hondas, I just discovered, should only be flushed when verticle.
 

wrxhoon

Well-Known Member
Joined
Apr 4, 2012
Messages
206
Likes
18
Points
18
Location
Sydney Australia
#19
Smokey as stated I will tape when flashing as I'm not familiar with 4 stroke Yamahas , I owned 2 stroke Yamahas in the past but they didn't have front pick ups. I know the Mercs with the front pick up will not overheat if the water pump fails and your are on the plane as water gets forced up the engine.

Doc, good to know but what happens when they are boat is in the drink? You can't start it tilled up, the pick up will be out of the water.