Help on Mercruiser TBI or MPI Injection Upgrade!

[bvprice]

Re: Help on Mercruiser TBI or MPI Injection Upgrade!

Originally posted by Boatist:<br /> Since water boils at 212 degrees you do not have any water in your engine at 240 only a little steam. Steam will not cool your engine at all. Even nascar engines only make about 20 laps when the water tempature hits 250 degrees. Many try and make it to next caution and about half bring out the caution from oil pan failure.<br /><br />Since marine engines are not pressureized and do not run antifreeze water does start to boil at 212 degrees and turns to steam.<br /><br />Do you ever start your motor with the out drive not in the water??<br /><br />Most engines run a thermostat in the 140 to 150 degree range. If it only over heats at low speed I dout it is the thermostat. Yes the rubber impeller could have all the ends worn off and not pump any water at low speed. Also possible to have a leak in the outdrive pivot area that allows all the water to leak out at low speed.<br /><br />If you have not already damaged your engine beyond repair you need to fix it before you use it.

Motor still runs fine. Just to clear things up, the motor didn't sit there and idle for days at 240 degrees. I realize I have a problem and will absolutely fix it. The limited amount of idle time and low speed cruising had a little effect on the motor. When it did heat up, I ran the boat to cool it down. Like I said I am new to this and was concerned when the boat ran hot. I asked a fellow boater (obviously un-informed) if this temp range was normal. He said that it was. But, even after this I was still concerned and kept an eye on the temp. I have run the boat out of the water, but always with ears. It starts and runs like a top. Always has.

 

[waterone1@aol.com]

Re: Help on Mercruiser TBI or MPI Injection Upgrade!

Titan, Yes, the raw water pump is the impeller in the outdrive. Boatist had a great idea to look at the rubber hose next to the bellows. I did have a similar problem with a thermostat that was stuck partially closed, it wouldn't allow enough water flow untill the raw water pump was spinning fast enough to force water through it, so I stick to my suggestion to replace the thermostat. Get the thermostat (and gaskets) from a marine dealer and make sure it is the right temp rating, most likely 143 deg. Replacing the thermostat will also give you an opertunity to inspect the housing and clean out any rust and scale build-up.<br />Between the hose check, a new impeller, a new thermostat and a clean thermostat housing, there is a good chance your problem will be solved. There are several other things that can cause this, but they are much more involved and expensive. Keep us all posted on how things go.

 

[bvprice]

Re: Help on Mercruiser TBI or MPI Injection Upgrade!

Originally posted by waterone1:<br /> Titan, Yes, the raw water pump is the impeller in the outdrive. Boatist had a great idea to look at the rubber hose next to the bellows. I did have a similar problem with a thermostat that was stuck partially closed, it wouldn't allow enough water flow untill the raw water pump was spinning fast enough to force water through it, so I stick to my suggestion to replace the thermostat. Get the thermostat (and gaskets) from a marine dealer and make sure it is the right temp rating, most likely 143 deg. Replacing the thermostat will also give you an opertunity to inspect the housing and clean out any rust and scale build-up.<br />Between the hose check, a new impeller, a new thermostat and a clean thermostat housing, there is a good chance your problem will be solved. There are several other things that can cause this, but they are much more involved and expensive. Keep us all posted on how things go.

I appreciate all of the input, I already have a new impeller and was going to try to get at it today. As far a the thermostat goes, I'll need to get that on Monday, unless my local Checker Auto carries marine Thermos. I doubt it does. I'll keep you updated.