New owner of the 4.6 engine and have questions
 

Hi everyone, I just bought a 1994 Renken 19 foot boat with the 4.6 mercruiser in it. I had a 77 merc 120 before so this engine is completely new to me.

My first question is, what should the max temp of the engine be on the trailer(I think my water impeller is on its way out because it was only running a few mins and I went up to about 150f. The muffs didnt suck in like my previous boat did after i replaced the impeller(but that was on a pre alpha drive so gen ii might be different) Is the thermostat also a 140 degree like on the merc 120?

My second question is, I noticed when I went to gun the throttle fast when it was on the trailer it hit a dead spot where the engine just started to die. Now on my 120 I had the same problem and had to rebuild the carburetor. Just wondering if I have to do the same here or is there another common problem with these engines like a bad fuel pump?

My last question is, I noticed there is some type of alarm under the dash. It actually sounded once after the engine was running for a while then I went to restart it and got the alarm sound when I put the key to run. But then I just put they key to off and then back and it was fine again. Anyways being though I had an old boat without any warning devices(you relied on yourself to keep a look out on the gauges lol) when does the warning alarm go off? Under what circumstances. For example if it was high temp, what temp does the alarm go off at? When my alarm went off the engine was off at the time.

Thanks for all the help!

I'm not familliar with the 4.6, but 150 is not too hot. The alarm is hooked to the 'vitals'. Oil press, water rep,drive lube, etc. if the key is switched on without starting, or the engine dies, the alarm will sound after a few seconds. If it comes on while running, you need to determine the cause.

Enjoy the new boat :drink:

Also be careful winding it up too high on the trailer, you can pull more water than the hose will provide and risk potentially eating an impeller.

I'm just guessing here, if your temp got up to 150 that fast you might need to look at that impeller and housing,or try flushing the cooling system out! rt930turbo is right, you will collapse your hose if revn up to high then you do risk the chance of damaging the impeller if not already damaged. I would guess that it is a 140 tstat on that motor.

You will get more accurate answers...
 

...if your questions are more accurate!

You have a 4.3 v6 Mercruiser.

Prime operating temperature is in the 180* range.

Likely it has an engine temperature alarm and an oil pressure alarm.

No matter, wisdom would be a new impeller and then run the boat in water and see what it might need. A garden hose/muff has its place, but not for running the engine out.

Buy a service book.

Thanks for the replies. Sorry it is a 4.3, I dont know why I was thinking 4.6 lol. For the alarm how does it sense one of the gauges are not in spec? Is the like a little computer chip that outputs a signal to the alarm? Im going to replace the impeller. Now I always used to remove the whole outdrive, When I was looking at it closer cant I just unbolt the lower half of the stern drive and still leave the upper attached to the boat? Thanks again

Get the service manual...
 

...for good directions and troubleshooting answers.

It will give you all the correct specifications and warnings.

Temp and oil pressure are just the standard, old school sensors. Nothing fancy. More likely the alarm will falter before the sensors do.

I will also add this. I mistakenly got a 190* thermostat and did not notice until installed. Mechanic had been specific for a lower temperature. NO MATTER... actually improved fuel consumption just a little and took care of occasional slight hesitation of hard acceleration.

Thanks. I do have a service manual but some of this stuff isnt in it. Today I noticed my shift cable bellow is cracked. My question is, if I dont replace it could it still go in the water without leaking? I dont remember how it is sealed in the gimbal housing. My ujoint and exhaust bellows are fine. Next year I would defiantly replace all of the bellows along with the gimbal bearing. I just want to get this in the water already lol. I am in fresh water also, no salt. I know if the ujoint bellow was cracked I wouldnt put it in until I put new bellows on but im not sure how the shift cable is sealed.

Also what makes the thunderbolt ignition different from other electronic ignitions? Thanks

The shift cable bellows will sink the boat faster than the u joint bellows. If it's cracked, replace it before you launch. Why are you concerned about the Thunderbolt ignition? It's a good fairly trouble free ignition and replacement parts are affordable. Don't worry about that but replace all of your bellows now, don't wait until winter or you will be replacing alot more than just bellows.