1998 7.4 mpi bravo 1 getting hot during high rpms

[alldodge]

Interesting stuff,.. Is this ian nheritance to just Bravos,.. .. Or is there 'Alphaitis' too ?

Was hoping an Alpha dude would answer this one in the last thread, but since that didn't happen, hopefully one will come in and clear it up if I mis-speak.

The Bravo uses a plastic cone bushing which is screwed into the hose which causes it to be held in position. Part of the hose extends past it and this rubber is what causes the issue with the Bravo. The fix is the kit which removes the screw in plastic bushing and replaces it with a tube and a rubber bushing which goes around the outside of the tube.

This does happen to the Alpha because it uses brass barbed fittings which go inside the rubber hose and is secured with hose clamps. The gets soft as all rubber over time but there is no swelling at the end

 

[jmarines]

Those pictures Alldodge posted were from my boat last year, on the thread below. My boat was doing the exact same thing you describe. It's so common that there's a name for it: Bravoitis.

http://forums.iboats.com/forum/engin...rc-7-4-bravo-3

It's a 2003 Crownline 225 with a 496HO, flushed every time it's taken out. Had 390 hours on it as of last weekend. Been in saltwater once in it's life for a weekend, when we took it to watch the airshow from Pensacola beach about 5 years ago.

I changed the water inlet for the Hardin kit without removing the engine. It was a major pain, description of the process is in the thread linked above.

There's a couple more pics of the drive with the hose and fitting removed in this thread:

http://forums.iboats.com/forum/engin...mostly-at-idle

Good luck!

Thanks you for posting the link !. The more I read the more it looks like this is my problem. Hopefully I will be able to get at it this coming weekend.

 

[shaw520]

AllDodge, Yes Im familiar with the brass through fitting on the Alpha,.. Ive never seen one choke up,.. but then again I see something new everyday!

 

[harleyman1975]

I'm curious to find out if it was plugged up!

 

[TyeeMan]

Years ago I had boat with a 3.0L/Alpha. I had the dealer install all new bellows and a new water tube. When I got the boat back the boat would overheat on plain.
After a lot of looking and questions here on iboats (back in the day when Don was on the board) Don said that water tubes came too long from the factory and would kink when the out drive was full down. He said to trim X amount off the hose and I'd be fine. Had the dealer trim X amount off the hose and all was fine.

I know you have a Bravo drive, but just throwing that out there as a possibility.

 

[jmarines]

No Title

I was finally able to remove the pain in the butt piece that's connected to the transom. Omg... what a pain.. I still don't know how I'm going to reinstall it.m the lower bolt will be the issue. Anyways.. it didn't look to bad as far clogged up... so looks like my next step will be a back flush. Getting the water hose setup as I type. I am now leaning to a through the hull water tube setup for thw seawater pump instead of going back to the stock setup that goes through the outdrive... any pros and cons about going that route?

 

[jmarines]

Well back flushing didn't yield anything except piece of mind .. water came through clean and clear. For about 8 minutes. Guess I'm back at square one.

 

[scoflaw]

Maybe its your gauge. Did you check it with an IR gun ? You'd know it if it overheated.

 

[alldodge]

They are a pain, and what makes them really hard is the exhaust Y-pipe. May need to remove a few things to get better access. From this pic I'm seeing the start of Bravoits

You could go thru hull and they work fine so long as your boat isn't real fast. If most of the hull comes out of the water then the placement of the pick up is critical. If not install on a fast boat it can suck air. You will need to disconnect the hose going to the transom, and it can be cut.

To verify before going any further is disconnect each hose going to each cooler. Need to look inside it input side looking for anything that does not belong. If you cannot see use a camera, and even your finger to fell around. Your garden hose does not move the same amount of water.

If it was mine I would lean toward installing the kit after a complete inspection

 

[tpenfield]

I'm thinking that this (Bravoitis) may be the issue, since it is a higher speed symptom at this point. The restriction is not as bad as some, but certainly not good either.

 

[jmarines]

I'm thinking that this (Bravoitis) may be the issue, since it is a higher speed symptom at this point. The restriction is not as bad as some, but certainly not good either.

So you think it could still be my issue even after seeing that it wasnt very restricted?

 

[tpenfield]

So you think it could still be my issue even after seeing that it wasnt very restricted?

It looks like the Bravoitis has reduced the opening by about half. . . I know some of the pictures on the Internet show the more severe cases of Bravoitis where the opening is nearly closed off.

If you find no other glaring issues, then I would get the Bravoitis resolved and try out the boat again at high speeds.

 

[NHGuy]

Exactly, there needs to be a good supply of cool water, and yours is reduced. So at higher rpms where the engine produces more power and heat the cooling can't keep up to the heat produced. Gotta give that a go, it won't get better only worse.

 

[tpenfield]

A bit of engineering speak . . . the cross-sectional area of the intake hose at the Bravoitis restriction is proportional to the 'square' of the diameter reduction. The flow resistance as the speed of the engine and related water flow increases is proportional to the 'square' of the speed increase.

So 1/2 of the diameter, yields 1/4 of the cross sectional area. Twice the speed results in 4 times the resistance.

Certainly could be something that only manifests itself at the higher speeds.

 

[jmarines]

Will do guys.. thanks for the advice. Looks like I'll be buying the kit to install. I've removed a alfa 1 gen 2 drive before.. is the bravo 1 similar? Is it me or does the bravo drive seem larger than a alfa drive? Maybe I need to invest in making a drive jack for removal and installation

 

[alldodge]

The Bravo is bigger and heavier, weights around 150 pounds, and a drive stand is a must for me, otherwise you need help. There is a thread on home made jack stands in the adults only section

 

[rick3452]

I had the same problem for quite a while, I changed everything nothing really helped so I did install a through hull seawater pick up that MerCruiser recommends, I did tee it into the existing hose going to the seawater pump and absolutely 100% cured everything . Now no matter how hard I run it, still stays dead on 160. MERC PART # 818170A2

 

[alldodge]

tee it into the existing hose going to the seawater pump and absolutely 100% cured everything

An additional pickup was added between the pump and the drive with a Tee fitting, and no more over heat. There was and still is a restriction between the drive intake and the pump, its just not an issue do to the additional feed.

 

[tpenfield]

The Bravo is bigger and heavier, weights around 150 pounds, and a drive stand is a must for me, otherwise you need help. There is a thread on home made jack stands in the adults only section

Yup, the Bravo is a bit heavier than the Alpha. . . Maybe 20 lbs. or so. If I'm feeling really strong, I can lift the outdrive off and lower it onto a dolly. I find the toughest thing is getting a proper stance to lift and handle the outdrive, especially with a swim platform in the way. Probably a bigger issue than the weight itself.