Mercrusier 470 starts slow when hot

[Blazeracer]

Hey all, I have a 1981 VIP with a Mersruiser 470. We had the motor out and did a reseal on everything last fall. Finally got her back in the water this weekend and while it ran awesome, pulled hard, didn't overheat or anything, it did have one problem. After shutting it off it turns over very slow when I try to start it back up. We let it sit for about 1/2 hour to swim and it picked up and started. Does anyone know the cause of this? Voltage it just fine. but my negative battery terminal gets really hot, like to the point where you can't touch it, and it's a big ole honking 2 gauge cable.

I don't want to hear that the motor is a piece of crap either. After going through some slow cruising to warm it up, a dude with a big $35,000 ski boat went blowing past us. I let him get about 100 yards ahead, I then gunned my little $1,500 17 foot VIP and that 470 caught and passed him within a 1/2 mile. I think the motor pulles like a freight train and is totally awesome. I just need some ideas to get the started to crank faster once it's hot.

Thanks in advance

 

[stonyloam]

Re: Mercrusier 470 starts slow when hot

I have had similar problems in the past (twice). Seems that the 470 starter has a rather long armature shaft and sometimes the shaft will bend or break over time and the armature will rub against the field coils and slow the starter down, it will turn slowly and draw lots of amps. I just replaced mine with a gear reduction permanent magnet starter, and it (so far) works great, and it is about 2/3 the size of the original making instillation (getting past the exchanger) a snap. Good luck. Glad you are happy with your "piece of junk" 470 .

 

[JustJason]

Re: Mercrusier 470 starts slow when hot

Google "voltage drop test" and do one with the motor hot. Also use an amp clamp so you can see what your starter is pulling when the engine is hot if the drop test passes.
You might be getting to much reistance when the engine heat soaks, but you need to test all the cables and connections first.

 

[badkins50]

Re: Mercrusier 470 starts slow when hot

first let me say that the 470's are a huge piece of crap thats why they stopped, just kidding , I couldn't resist. I really enjoy mine. so what if I have to do alittle more maintenance than the other guy. i've never seen a boat that doesn't require some every now and then. I don't have an answer for you, I've never encountered that problem, at least yet. Good luck.

 

[dry dock]

Re: Mercrusier 470 starts slow when hot

you might need to have the starter rebuilt , that how mine acted when it got hot. good luck............

 

[q5ka]

Re: Mercrusier 470 starts slow when hot

Agree with shaft being bent as a possible problem. As everything is warming up around that starter, things start expanding. There could be a few other problems to consider also. One could be the starter needs a rebuild as the brushes are worn and as things also expand due to heat, the contact connection gets worse. Another issue could be a form of vapor lock. One other issue could be simple bad connections of the starter leads.

How I would test it is I would take it out (or put on muffs) and wait until it acts up again. At that moment, pull the plugs and see how well the motor turns over. It will be faster but is it still acting like it is working hard. If it turns super easy, you possibly have some form of vapor lock. If not, you may have electrical or starter problems. Clean your battery wire connections at both ends (battery side and relay side). If that is not it, starter time.

I would bet something during heat expansion so bad wire connection or starter issue but I like to start with the potential free/cheap fix problems and work up to the more expensive fixes.

 

[Fireman431]

Re: Mercrusier 470 starts slow when hot

Remember heat shields? I used to use them with hot rod engines (yes...I know those are cars). Concept is still the same. Higher horsepower in a minimally ventilated area creates excessive heat. When the starter heats up too much, it will drag. Heat shields were a life saver to me plenty of times.

...not saying the starter doesn't need a rebuild. Are those equipped with mounted solenoids or remote solenoids?

 

[Blazeracer]

Re: Mercrusier 470 starts slow when hot

Thanks for the great advice. I'll start with the simple stuff first, the cables. I took a quick look at the cables today when I removed the battery for the week (I park my boat and work and don't the battery getting lifted) and there is a slight amount of corrosion. I was also thinking of a heat shield, but another possibilty entered my mind today. I used to have an old Chevy that needed metal spacers on the starter to keep it from binding. I'm gonna look through my tool boxes and see if I still have any laying around and try that also.

However, a nice little gear reduction starter would be awesome. I put one on my S10 with a 350 and what a difference it made. Where did you get one from that fits this motor because I am thinking the bent shaft is the culprit anyway? From I've heard the automotive 460 starters won't work on this "piece of crap" motor.

BTW, just picked up a stainless steel prop with a little more angle on it. The guy said it will get a couple more mph top end. We'll see this weekend.

 

[stonyloam]

Re: Mercrusier 470 starts slow when hot

However, a nice little gear reduction starter would be awesome.....Where did you get one from that fits this motor......

I got mine from my local auto electric shop (http://www.northstarautoelectric.com/), but I think these guys have them. http://bpi.ebasicpower.com/ .