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View Full Version : MERCRUISER 470(3.7L) slow cranking??


81 enchanter
08-13-2007, 12:22 PM
just picked up my new(to me) sportfire with a mercruiser 470. it seems to crank slow but always started, its charging at 14volts. and the battery didn't need much of a charge when i brought it home and checked it. is this normal?

83PREDICTOR
08-13-2007, 12:32 PM
did you do a load test

81 enchanter
08-13-2007, 02:48 PM
load test came back good and i put in my brand new battery from my camper.

twright55
08-13-2007, 05:58 PM
I have the same motor and the same problem.
THose starter motors are an ancient design and they crank slow even when in perfect condition. THe older they get, the slower they will crank.
Mine cranked so slow on such a regular basis that I was surprised the motor ever started. THen once on the water on a really hot day, it cranked so slow that the engine wouldn't start. I was stranded for a few hours till everything cooled down enough that the motor cranked over just fast enough to start.
I bought a modern style replacement for $99 (the modern replacement has a built in solonoid and is much shorter but larger in diameter.) Now it cranks over fast like an engine should and starts every time. Not to mention, the modern replacements cost half as much as the original replacement (which are officially NLA.)

81 enchanter
08-13-2007, 06:11 PM
I have the same motor and the same problem.
THose starter motors are an ancient design and they crank slow even when in perfect condition. THe older they get, the slower they will crank.
Mine cranked so slow on such a regular basis that I was surprised the motor ever started. THen once on the water on a really hot day, it cranked so slow that the engine wouldn't start. I was stranded for a few hours till everything cooled down enough that the motor cranked over just fast enough to start.
I bought a modern style replacement for $99 (the modern replacement has a built in solonoid and is much shorter but larger in diameter.) Now it cranks over fast like an engine should and starts every time. Not to mention, the modern replacements cost half as much as the original replacement (which are officially NLA.)

thanx for the advice!! good to know it isn't a major problem just a problem. do you know where you picked up the new one from and how much of a pain was it to replace? it dosen't look like much fun. thanx!!

twright55
08-13-2007, 08:56 PM
I found the place on Ebay, but their store happened to be close to where I lived in Orlando, FL. I can't remember the name, but if you search Ebay with 'starter motor 470', I bet it will come up. They rebuild them there...it's a huge warehouse with NOTHING but starters and alternators!
Actually, I think the starter was $89 plus tax.
There were to problems with the install.

First, the old wiring in my boat was not enough to kick off the solonoid. I had to keep my old solonoid, to kick off the solonoid on the starter!

Second, the bolts did not fit the new starter. The reason is that the new starter was much fatter than the original (probably why it was so much more powerful.) So the old bolts were to long to slide in at an angle to get them in place. So I had to cut down the threads and make the bolts much shorter before I could get them in. It's hard to describe with words, but when you try to get the bolts onto the new starter, it will be obvious.
Luckily, I think the bolts work primarily in shear (not tension or pull out), so I think shortening them did not seriously weaken the connection. Another other option would be to install studs instead of using bolts (this would actually be much better, but I wasn't sure where to even buy the correct size studs.)

I hope that doesn't scare you off the idea of the newer sarter! It's not that difficult to deal with. And the superiority of the new style starter is significant.

81 enchanter
08-13-2007, 11:40 PM
I found the place on Ebay, but their store happened to be close to where I lived in Orlando, FL. I can't remember the name, but if you search Ebay with 'starter motor 470', I bet it will come up. They rebuild them there...it's a huge warehouse with NOTHING but starters and alternators!
Actually, I think the starter was $89 plus tax.
There were to problems with the install.

First, the old wiring in my boat was not enough to kick off the solonoid. I had to keep my old solonoid, to kick off the solonoid on the starter!

Second, the bolts did not fit the new starter. The reason is that the new starter was much fatter than the original (probably why it was so much more powerful.) So the old bolts were to long to slide in at an angle to get them in place. So I had to cut down the threads and make the bolts much shorter before I could get them in. It's hard to describe with words, but when you try to get the bolts onto the new starter, it will be obvious.
Luckily, I think the bolts work primarily in shear (not tension or pull out), so I think shortening them did not seriously weaken the connection. Another other option would be to install studs instead of using bolts (this would actually be much better, but I wasn't sure where to even buy the correct size studs.)

I hope that doesn't scare you off the idea of the newer sarter! It's not that difficult to deal with. And the superiority of the new style starter is significant.


thanx for the info, i think i am going to try to get the rest of the season out of it and replace it this winter! good to know someone else on here with one of these boats!!

ButchF20
08-15-2007, 04:43 PM
Hey guys,

Try Breezeworks website, they are exclusively 470, 3.7 fans and have e wealth of info on these engines.
Thanks,
Butch