Question on cranking a big block

[paulrfrancisco]

I have twin 1990 454's in my boat... I always thought they both seem to crank over rather slowly. Not laborous like its a advanced timing problem but just a little slower than my previous boat that only had a 260hp V8 - 350ci... Would it be expected that big blocks dont spin over as vigourously as a small block V8? One other item to mention is I believe that both batteries are "deep cycle" batteries, (in good condition) Would "starting" batteries provide a more vigorous cranking, in general?

 

[tommays]

Re: Question on cranking a big block

i have never owned a big block but have seen plenty of batterys that over time started to deliver a LOT less cranking amps as they got old<br /><br />battery cables and connections also wear out over time and cause a lot of voltage drop<br /><br />i have found this to be true on any size engine<br /><br />the only way to be sure is a load test on the battery and then work from there<br /><br /><br />tommays

 

[paulrfrancisco]

Re: Question on cranking a big block

Yes, I understand those points, however I have flooded both engines on several occaisions, and had to crank them both for extended periods without any diminished cranking speed or noticible lose of battery power. In addition, what are the chances that if the batteries were bad, or going bad, that they would both exhibit the same symptoms on each engine.<br /><br />My question is this, will a deep cycle battery not kick the starter moters as well as a starting type battery? or do big blocks simply just exhibit this condition as a matter of course?

 

[ron7000]

Re: Question on cranking a big block

Originally posted by Paul032562:<br /> Would it be expected that big blocks dont spin over as vigourously as a small block V8?

not at all.<br />I had a '89 truck with the 7.3L diesel. After replacing the starter, which was half the size of a standard chevy 350 starter that would be on most boat engines, it would crank like mad. Engine cranking is primarily due to the starter and it's gearing. It's most likely the starter, how long since they were rebuilt/replaced? I've also noticed that old model starters, maybe mid 90's and earlier, just crank slow. I stopped getting my original 1975 starter rebuilt and bought a brand new replacement from overton's and that thing cranks like mad now.<br /><br />For engine starting, a "starting" battery is better than a deep cycle because they are designed to release maximum power rapidly, and will do that longer than a deep cycle will. The deep cycle is designed to output a conistent but much lower amount of current for a long time. A lot of starter cranking on a deep cycle will give the appearance that the battery is going dead, but give it a rest then it comes back to life. This is because it internally gases due to it's deep cycle design, and slows it's rate of discharge. If when you first turn the key and engine cranks slow, then it's not due to a "deep-cycle" battery, unless the batteries are weak to begin with. Only if you're cranking longer than 5 seconds would you notice.<br />Most deep-cycles are dual-rated, not as great as a pure starting battery but plenty good if you're only running one battery.

 

[paulrfrancisco]

Re: Question on cranking a big block

Thanks Ron, as far as the age of the starters, I dont know.. probably 1990 for all I know.. I only bought the boat 2 years ago...<br /><br />Given you desc. about the nature of the battery drain I assume they're starting batteries because its slow right off the get-go and doesn't diminish. I guess at this point I would conclude that the starters are normal. And maybe I should have the batteries load tested to be sure they're OK as well...<br /><br />thanks for you help.