1998 7.4 mpi bravo 1 getting hot during high rpms

[jmarines]

Okay guys.. here's the deal. I purchased a new to me 1998 rinker with a 7.4 that didn't see any usage the past 2 yrs. I had to get the fuel drained due to bad gas. I also replaced the impeller due to not knowing the condition . The impeller I removed looked great but I installed a new one anyways. As soon as I took it out the motor started to overheat as soon as I went on plane. I went ahead and replaced the thermostat along with the manifolds and risers. The distributor cap...rotor and spark plugs were also done when the fuel was removed. I must say.. she fires right up... no hesitation . I get on plane quick .. which just feels great but I notice around 3000 rpms I'm sitting right at 180 degrees and if I accelerate to a higher rpm the temp rises. I backed off once it reached 200 degrees. Am I being over cautious and worried about something I shouldn't be or do need to investigate this issue? I've always thought these things were suppose to run cooler than 200 degrees. I also checked the exhaust flaps (I think that's what thier called) where the rubber coupler that comes off the elbow and they worked great..no sticking or and type of weird noise when I pushed on them. My water pump that's mounted on the motor seems to be okay.. no movement on the pulley or water dripping. The hose from the transom to the sea water pump was replaced due to it looking pretty rough on the end that clamped down. When I have it on muffs I removed the drain plugs on the manifolds and both flowed alot of water out of them which makes me think the seawater pump is operating normally. I have good flow coming out the rear of the boat. I do have a repair manual .. I see this there's a cooler coming off the hose from the sea pump.. should I be looking in that area? Sorry for the long post but I'm just trying to give as much info as I can. Any help would be appreciated

 

[alldodge]

You should have two oil coolers (power steering and oil) and both should be checked to see if there is anything blocking flow. You shouldn't be running much more then 180 degrees
http://www.mercruiserparts.com/bam/subassembly/31918/2705/150

Has the boat been used in slat or brine water?

The hose from the transom to the sea water pump was replaced due to it looking pretty rough on the end that clamped down

Suggest removing the transom fitting to this hose and see if there is a restriction there

 

[Bt Doctur]

Or a case of Bravoitis" Has the drive been removed to check?

 

[jmarines]

The boat has been run in salt water for the last 9 yrs.. with little use is what he informed me. The last time the outdrive was pulled was a yr ago... the seals needed replacing. I will check the oil and power steering coolers for obstructions. The transom fitting will defiantly be a chore.. it's pretty much surrounded by alot of things. The reason why the hose was replaced is because on the seawater pump side it looked to be tightened down to tight which caused it to become "swollen " looking on the end. Not sure if that makes sense. I will defiantly see what I can do about removing the fitting.

 

[alldodge]

Being in salt you could very well have Bravoits. Its where the hose at the transom on the engine side is collapsing

 

[shaw520]

Wow,.. Bravoitis,... is there such thing as Alphaitis ?

 

[Scott Danforth]

Also since this is a new to you boat, replace the t-stat. I would also verify the temps with an IR temp gun which is alot more accurate than the dash gauge

 

[tpenfield]

Having just gone through a season long troubleshooting of a similar problem on a similar engine, I feel highly qualified to answer this question . . .

. . . it is probably a sea shell stuck in the outdrive water tubing at the bell housing . . . (kidding, but maybe not)

The coolers can trap marine growth and restrict the flow of raw water through the engine. So, you can check the several coolers that run from the sea water pump up to the thermostat housing. Backflush as you see fit.

If you are in salt water, then the sea shell thing may be a possibility. Marine life can/will grow inside the water duct of the outdrive and some can break loose and flow up the inlet and get trapped at the smaller hose that leads from the bell housing to the transom assembly.

If you have the boat out of the water, you can easily check for Bravoitis, as mentioned, and remove the outdrive to check for any obstructions in the water intake hose, etc.

 

[jmarines]

Being in salt you could very well have Bravoits. Its where the hose at the transom on the engine side is collapsing

Holy cow... that's bad! Would I still consider this if the system was flushed after every use? The reason why I'm asking is when I pulled the manifolds and risers iffy they looked pretty good... I was,told they looked like they came off a fresh water boat.

 

[jmarines]

Also since this is a new to you boat, replace the t-stat. I would also verify the temps with an IR temp gun which is alot more accurate than the dash gauge

Forgot to mention the tstat was replaced when I did enjoy the impeller. I didn't even think about the guage malfunctioning. I'll definitely check that next time I go out.

 

[jmarines]

Having just gone through a season long troubleshooting of a similar problem on a similar engine, I feel highly qualified to answer this question . . .

. . . it is probably a sea shell stuck in the outdrive water tubing at the bell housing . . . (kidding, but maybe not)

The coolers can trap marine growth and restrict the flow of raw water through the engine. So, you can check the several coolers that run from the sea water pump up to the thermostat housing. Backflush as you see fit.

If you are in salt water, then the sea shell thing may be a possibility. Marine life can/will grow inside the water duct of the outdrive and some can break loose and flow up the inlet and get trapped at the smaller hose that leads from the bell housing to the transom assembly.

If you have the boat out of the water, you can easily check for Bravoitis, as mentioned, and remove the outdrive to check for any obstructions in the water intake hose, etc.

Thanks for the info.. I'll definitely take a look at the coolers

 

[jmarines]

You should have two oil coolers (power steering and oil) and both should be checked to see if there is anything blocking flow. You shouldn't be running much more then 180 degrees
http://www.mercruiserparts.com/bam/s...31918/2705/150

Has the boat been used in slat or brine water?


Suggest removing the transom fitting to this hose and see if there is a restriction there

Are there 3 coolers in the cooling system? I see what appears to be coolers connected to hose number 8,9,10 in the diagram in the link that you provided

 

[jmarines]

Almost forgot to ask.. to backflush.. I assume stick a water hose in one end and crank it up... I would also assume to have the flow of the water hose going in reverse to what the normal direction of water flow would be. Just wanting to be sure so when I do it this coming weekend there will not be any .
.Oh **** moments.

 

[Scott Danforth]

you backflush with the hose only, starting at the thermostat housing and working backwards

 

[alldodge]

Are there 3 coolers in the cooling system? I see what appears to be coolers connected to hose number 8,9,10 in the diagram in the link that you provided

There are 3 coolers are item 24 (PS cooler) and the one which is vertical under number 8 (oil cooler).

The one between 9 and 10 is the cool fuel module for your fuel injection

 

[tpenfield]

Easiest way to backflush IMO is to disconnect the exit hose (lower) on the sea water pump and force water (garden hose) down the hose that lead to the t-stat housing. You should be able to see any solids in the bilge.

 

[Bt Doctur]

Would I still consider this if the system was flushed after every use?
Definitely what happens is the alum housing build up corrosion and forces the opening closed.his is from a Fla boat that was stored indoors for 3 years.

 

[jmarines]

Thanks guys for all the help.

 

[45Auto]

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!

 

[shaw520]

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