First time out - didn't last long

[Stephen1]

I have a 90hp I re-built 4-5 yrs ago. Today was the first time out this year. I winterized it last fall and everything was fine. Today, after launch I was at idle heading thru a channel when the over-temp buzzer went off. I have a temp gauge but unfortunately wasn't monitoring it as I should have. I immediately shut it down- I waited several times for it to cool down but each time at idle the buzzer went off again. I used a trolling motor to limp back. So I don't want to jump to conclusions but it would seem the thermostats are the most likely suspects, even though they are fairly new.

Would you experts concur? And since it's been 4-5 yrs. since I re-built this- it would appear those 3 bolts are rather difficult to get a socket or wrench on- is there a secret that I forgot about? Or just how much dis-assembly is there?

 

[Stephen1]

Re: First time out - didn't last long

Silly me- forgot to add that the water pump was replaced during the re-build and I was seeing a very strong stream from the pee hole today.

 

[SparkieBoat]

Re: First time out - didn't last long

sounds like t-stat, replace them both and flush out the motor as much as possible, also could be some sand stuck in the block. defiantly figure this out, you could remove t-stats and test run it and see if it over heats again, this will tell for sure.

 

[TD_Maker]

Re: First time out - didn't last long

Great motor. Sure sounds like the thermostats are stuck. Not a fun job on the V-4's for sure. Be patient and make sure the kids are not around when you change them. There may be a few curse words flying around. Also, it HAS been 5 years since the water pump impeller has been changed, so don't necessarily take it for granted it is supplying enough water (or pressure) at idle speeds.

 

[ezeke]

Re: First time out - didn't last long

If you are going into the thermostats, buy the kit before you start so that you have all of the necessary parts: http://www.iboats.com/mall/partfind...gd_poid=111072&gd_row=43&**********=494088900

It's good shop practice to replace the cylinder head gaskets when you have an overheat, so change your water passage deflectors while you are at it.

 

[DJ]

Re: First time out - didn't last long

The t-stat block is a lot easier to access if you follow this:

1. Remove the cover at the top of the exhaust housing (leg).

2. Remove the bolts that hold the lower pan to the engine block.

You can gain about 3" which should allow you to get to all three, reasonably well. Use a 1/4" drive with a swivel.

 

[Stephen1]

Re: First time out - didn't last long

I appreciate everyone's feedback. I just checked all the receipts from the re-build, it was June 2007. That goes to show you how much fun we've had with it. It just seems like it has been 4-5 yrs.

DJ- thanks for the tip- I thought I could recall getting them out before I pulled the whole engine. The bottom pan is able to come back just enough to just barely get them out. I'll get the parts and then proceed.

The temp went up to 210-220 degrees - should the head gaskets be replaced for sure? I guess it'd be a good excuse to replace the deflectors too, however.

 

[McGR]

Re: First time out - didn't last long

Before you start tearing into things too far, make sure the alarm isn't erroneously beeping. Earlier this year I sold my old boat with a Johnson V4. The first time I went to start the motor this spring was in front of a potential buyer. For the first time ever, the alarm was buzzing away when I started the motor. I disconnected the buzzer and demonstrated the motor. After the potential buyer left, I decided to take a closer look at the alarm situation. I briefly inspected a few things. The only suspect thing I found was a loose battery terminal. I'm not sure if this can cause the alarm problem or not. Nonetheless, I tightened it up and re-tested the motor. The buzzing was gone, better yet, the guy came back two days later and bought the boat.

 

[Stephen1]

Re: First time out - didn't last long

I had installed a temp sensor after my last re-build so I could see the temp was up at 210-220 degrees and normally it is 160, so unfortunately I think the prognoses that I need to replace the thermostats is probably right on.

 

[ezeke]

Re: First time out - didn't last long

It's just as likely to be the water passage deflectors as the thermostats.

 

[Stephen1]

Re: First time out - didn't last long

What actually happens to the deflectors? As I recall they are just these rubber tubes wedged into special places in the water jacket of the head. Do they disintegrate over time or actually come out of place?

 

[ezeke]

Re: First time out - didn't last long

What happens is that the deflectors get in the passages where they don't belong and block the flow of water, causing that part of the cylinder bank to overheat. Click the thumbnail and look at the lower cylinder closely. That was caused by the water deflector.

In the diagram are arrows that show how water should flow.