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305 to 383 conversion overheating a message for rod stewart

J

jrgiust

Regular Contributor
"I put the 383 in, goes good,

"I put the 383 in, goes good, but is overheating> I took the seapump off, put the water line to the hose where the sea pump out went, and it doesnt seem to get enough water. If I put the water line to the cooler at the back of the engine on the right side what do I do with all the little lines that branch off from where the sea pump out was???"
 
"jeff;

Check where the hose

"jeff;

Check where the hose connection from the transom assembly turns and connects to the PS cooler. It makes a real tight 180 degree turn and if you are not careful the hose will kink and just about close off.
That's my first thought.

I am not sure what all the small lines you are talking about are. My 6.2 did not have any like that. Where do they go to?

You may have the coolfuel III module; maybe they belong to it. Mine has coolfuel II, which is plumbed right into the cooling water inlet line low on the port side just behind the port side motor mount.

You should get them plumbed into a water supply somewhere. You may have to T into the cooling water inlet hose with some pipe fittings and take a cooling line off there. Best place to do this is likely along the port side low just before the hose turns upwards to go to the T'stat housing. That would be the most accessible spot.

Rod"
 
"jeff;
Another thought.
Chec

"jeff;
Another thought.
Check your cooling water hose from the drive leg to the outside of the transom assembly for kinking.

Are you test running it on muffs?
If so, make sure you have plenty of water to the muffs. There should be excess water squirting out the side of the muffs.

Lastly, try disconnecting the cooling water inlet hose at the T'stat housing and run it into a bucket for 30 seconds idling at 1000 RPM. If you are getting enough flow the bucket should fill in 30 seconds or so. If not, you have an obstruction somewhere.

Rod"
 
"Thanks for all the info, you

"Thanks for all the info, you guys are great. I had a pinched line, it seems to be good now. I went from 45mph to 60mph. Now I have to play with props."
 
What is your WOT RPM?
Don&#39

What is your WOT RPM?
Don't get too nuts until you get a few hours on it.

Did you get the shift interrupt switch wired up OK?

Rod
 
"Hey its me again. I took the

"Hey its me again. I took the thermostat out and its running 140 on the gauge instead of 185 but the exhaust is super hot. What are those plastic elbows with the two lines going to them at the bottom of both exhaust manifolds? I took the bottom line off of one and hot water if coming out the bottom of the exhaust and cold water is coming out the line. It seems like they are fighting against each other. My 305 didn't have those plastic T's or check valves or whatever they are. Should I just take all the plumbing off of my other engine and use that? And my RPM is 5000, I think that's bang on. I get good holeshot and good top end."
 
"I know on my OMC, the thermos

"I know on my OMC, the thermostat offers restriction to make some or most of the water want to flow through the manifolds rather than enter the engine block- I know Merc is a bit different, but in case Rod doesn't show...might try putting the stat back in...."
 
I tried it in the lake with th

I tried it in the lake with the stat in and the engine kept shutting down on me. It's a 160 stat. I came home and took it out and tried it on the hose without the stat.
 
"jeff;
I am surprised you are

"jeff;
I am surprised you are having any temp issues at all. Mine is running with an Alpha II 1.47 ratio, and its cool. Never over 170. Its running a 160 stat.
185 is OK, you won't hurt anything BTW.

Mine has a hose from the T'stat housing to a T fitting on the bottom of each manifold. The bottom of the T on mine is where the blue plastic drain plug goes.

My manifolds run about 185-190 and the riser/elbows run about 85-90; all with 70 lake water. These are all with an IR temp gun. You should be able to put your hand on the riser elbow without pain. BTW, the risers on mine have another supply of water that comes from the T fitting on the top of the t'stat housing to the base of each riser. Thats why they are colder than the manifolds. This is surplus cooling water that goes directly from the t'stat housing to the risers. Is yours so equipped?

If your exhausts are running really hot, that sounds like insufficient cooling water flow. Are you sure you have enough water flow? Are you sure your water inlet line is not plugged somewhere?
Did you change the impeller?
Maybe you should do a cooling water flow test so you know where you are at. It would be a shame to overheat that nice new 383.

Rod"
 
ATTENTION ROD STEWART ITS JEFF

ATTENTION ROD STEWART ITS JEFF HERE CAN I PLEASE HAVE YR PHONE # IWOULD REALLY APPRECIATE IT THANKS
JEFF
 
"The exhaust is still getting

"The exhaust is still getting pretty hot, still seems like not enough water flow. I was told that a Alpha GenII has a higher flowing water pump than a Alpha One like mine. I just ordered a transom mounted water pickup, I'm going to remove the impeller from my OD, plug the water port and install the sea water pump, that should give me enough water. I HOPE."
 
"I didn't think it was goi

"I didn't think it was going to be that much, but oh yah. When you hit the throttle, the boat wants to corkscrew."
 
"Jeff;
OK, I missed that you

"Jeff;
OK, I missed that you are running an Alpha One. That may be true that the Gen II flows more water than an Alpha One. Gen II's were offered for a while with the 330 hp 454's.

A thru hull pickup sounds like your answer, and reinstall the belt driven pump. The belt driven pump flows about twice the water that a Gen II drive does. It's good you still have all those parts, right?

Don't take the drive impeller out. Leave it in and cut the hose from the leg to the transom plate. This will allow the impeller to still pump water up around the upper gear case. Essential to keep it cooled because when you are cruising the upper gear case is out of water, and will not cool properly without that pump flow.

Kurt;
The ECM that comes with the 6.2 MPI is properly tuned to deliver the required fuel for the 383. There are of course no jets to mess with.

Here's the thing though: The ECM is designed to run with the exhaust backpressure of a Bravo drive leg. I am running side hull exhaust outlets wih 4" exhaust hose connections, which is less restriction. I have noticed mine wants to miss a little in cruise range up to about 2800 RPM. I am guessing the mixture is a little lean in this range.

Above 2800 RPM it runs smooth and strong.
I have just put in a pair of Hardin 4" silencers to quiet it down a little. These will also add some backpressure, so I am hoping they will help the missing issue. Time will tell.

Jeff; what exhaust are you running with yours?

Rod"
 
"I'm just running through

"I'm just running through the leg for now, untill I can Quit finding stuff that I have to buy to get it cooling right. Maybe next year I'd like to put a silent choice kit on if I have the room for it, my boat has a big swim platform. I was just thinking of something, I probably have to buy some sort of strainer for that pickup right?"
 
"About that impeller in the OD

"About that impeller in the OD, should I just T that line into the main line and run both?"
 
"Jeff;
You can tie the leg wa

"Jeff;
You can tie the leg water line into the belt driven line I would guess; that would give you a backup. You could T them together at the inlet to the PS cooler if there is room.

You should definitely install a seacock at your thru hull pickup, as well as a strainer if you boat in water that has any amount of floating debris. Drive leg pickups are submerged where the water is cleaner, but hull pickups see surface trash.

If your current Alpha leg pump was not keeping up to demand, your seawater pressure sensor would see low pressure, and that would explain why your ECM was mysteriously shutting you down.

Rod"
 
"Ya, that would make sence abo

"Ya, that would make sence about the shutting down if it has a pressure sensor. What is a seacock, my wife is even more curious than me?"
 
Tell her it's not what she

Tell her it's not what she thinks! (But I guess she can make it into whatever she likes!)

It's just a shutoff valve right at the thru hull inlet that you can close if a hose breaks and your boat starts to flood. It's a Coastguard requirement for any hull penetration that is below water line.

Rod
 
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