10:1 compression on stock starter?

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

10:1 compression on stock starter?

Postby SthrnStyle3 » Thu Sep 03, 2015 11:19 pm

I just got the chance to fire my boat up for the first time since the rebuild. On one battery, the starter barely turned it before stopping. So I hooked a second battery to the first, in parallel. This second battery was out of my truck, so I know it was good. It still didn't have enough to turn it over. So then I had to add a 60amp battery jumper to it and that did the trick. The starter seems to be engaging fine. It acts like a starter with a weak or almost dead battery but the battery isn't. My question is what should I be looking at? Is it too much compression for an old stock starter? I was told it could be timing but I don't see how that could be it if the starter is having the this problem right from the second it's engaged. To me it doesn't seem like it's fighting a motor that's firing too advanced. :dontknow:
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

Hardtail
Site Supporter - I
Site Supporter - I
Posts: 251
Joined: Sat May 02, 2015 9:35 am

Re: 10:1 compression on stock starter?

Postby Hardtail » Thu Sep 03, 2015 11:26 pm

Put an Amp probe on the Positive wire to see how many amps you are drawing when you are trying to start, that will tell you what you will need to supply to start that motor, or if the starter is weak. A good battery will produce 300 plus amps, 2 good batteries will produce twice that, if you need more than 600 plus amps to turn over the engine, you will need a compression release when starting a very high compression motor. NOTE: You will need to use a DC amp probe to do that.

User avatar
swampsquatch09
Site Supporter - III
Site Supporter - III
Posts: 393
Joined: Thu Dec 13, 2012 9:13 am
Location: Mont Belvieu, TX

Re: 10:1 compression on stock starter?

Postby swampsquatch09 » Thu Sep 03, 2015 11:46 pm

Check to see if the engine and starter have good grounds to the battery, seen the problem had the problem
14ft Maxcraft, 70" WW Signature Series 320 lycoming
:texas:

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Fri Sep 04, 2015 12:00 am

What should I be looking for? High amps or low amps and which will tell me what? I've got a field piece multimeter but I've never measured amps on DC current, just AC current with the clamp. The only setting I see on it is measured in mA. Will that measure high enough for the cranking amps? I'm assuming you probe the negative terminal of the battery and the positive nut on the starter??
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

Hardtail
Site Supporter - I
Site Supporter - I
Posts: 251
Joined: Sat May 02, 2015 9:35 am

Re: 10:1 compression on stock starter?

Postby Hardtail » Fri Sep 04, 2015 12:38 am

You Can also measure volts which is easier because a digital meter will do DC and AC current, if your voltage drops way low you will then know the amps are too high or the batteries are weak, but that won't tell you if the starter is insufficient, you said when you put 3 power sources to the starter it turned over and started, so I'm thinking the power source was not strong enough. AMPS tells
what is needed for wire size to support a load, High compression requires high amperage, and the voltage has to be 10 to 12 volts for the starter to spin fast enough to start your motor. So for the easiest test watch the voltage drop when starting, with 1 or 2 batteries, and then with 3 Batteries. If the volts drop way down then you could have a loose connection, bad batteries, bad starter, OR
too small of wire from battery to starter. #4 gauge copper for 1 battery, #2 gauge for 2 batteries etc...

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Fri Sep 04, 2015 1:25 am

I'm using the same battery cable I've always had on my boat. I'll have to check but I think it's either #2 or #4.. I'll work on measuring the voltage drop and while I'm at it, I'll clean up the connections better. My buddy is working on getting me a high torque starter. I have one I bought from a guy but when I mount it, the starter gear is meshed with the flywheel, with out the starter being engaged. So we went with the old stock one. The original battery didn't work so I tried the one from my truck, which was good and when that didn't work, we just started adding more juice to it, just to get it running. The compression is more than what I had, but it's not extreme either.. It's around 9.8:1 maybe 10:1. I'm sure there's people out there running more compression than that. I'm hoping to only run one battery, because I don't have a spot to mount a second one. Does this sound like it could be timing?? Or is it more likely to either be the battery or starter?
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

Gary S
Site Supporter - I
Site Supporter - I
Posts: 1589
Joined: Wed Mar 03, 2010 3:30 pm
Location: Redlands

Re: 10:1 compression on stock starter?

Postby Gary S » Fri Sep 04, 2015 7:59 am

How hard is it to pull thru by hand? With mags off. I agree with swamp,check your cables. I have had ends look perfect and do the same thing your describing. You can use a good set of jumper cables to bypass the tables and see if this is the problem.

User avatar
kwanjangnihm
Site Supporter - IV
Site Supporter - IV
Posts: 1905
Joined: Sat Mar 30, 2013 8:23 pm
Location: Bartow FL

Re: 10:1 compression on stock starter?

Postby kwanjangnihm » Fri Sep 04, 2015 8:11 am

kwanjangnihm wrote:Install larger battery cables! (positive, negative & ground to rigging)

Look at the chart below - I replaced my 4 AWG cables and went to 1\0 AWG. Same battery spins my AV-540 with authority now!

The bigger cables allow 88% more energy to be utilized over the smaller diameter cables.

Image

I also installed military truck battery terminals that allow 4 times more current through them over lead type.

This may not be your only issue, but it will eliminate any doubts about your cables! :rebel:
" I don't care who you are back in the world, you give away our position one more time, I'll bleed ya, real quiet. Leave ya here. Got that? "

One Eyed Gator
Southern Airboat Member
Posts: 1258
Joined: Wed May 30, 2007 11:33 am
Location: Ocala,Fl

Re: 10:1 compression on stock starter?

Postby One Eyed Gator » Fri Sep 04, 2015 9:20 am

If it is a new or build with fresh paint check your ground locations.

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Fri Sep 04, 2015 11:18 am

Ok I checked the grounds and they seem ok. I tried to measure the volts when starting, but it fires off before I can get a reading. Last night I left the battery on charge all night, on 2 amps. Today it will start (multiple times) but it really struggles. Sometimes the starter will stop because it doesnt have enough force to turn it over, but if I let off the key and try it again and again, it will work again. But even with it working, it is really slow and struggles. The only good thing now is that the motor pops of so quick that I don't have to rely on the starter for long.. I should also note that it is really hard to turn the prop by hand. I don't know if most gearbox boats are like that or not.. It take two hands and a lot of pulling. I also noticed that when I shut it off everything stops almost instantly. Is it the compression or is the motor just still tight from the rebuild??
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

Dr.Dan
Southern Airboat Member
Posts: 32
Joined: Tue Mar 17, 2015 11:32 pm
Location: Calgary, AB

Re: 10:1 compression on stock starter?

Postby Dr.Dan » Fri Sep 04, 2015 11:50 am

As you mentioned, 10:1 is not super high. A stock sbc starter should turn that no problem. If it's super fresh and tight maybe that'll slow it down a bit. Wiring or ground could be contributing too.

After you confirm the wiring is good, a high torque mini starter is a good idea anyway. A decent hitachi style mini starter is much stronger and much lighter than then old stockers. At summit racing or any other speed shop they can be had for a decent price. They sound cool too. They're all I would ever use on a sbc now.

dd

terrible ted
Southern Airboat Member
Posts: 2819
Joined: Tue Aug 12, 2008 8:07 pm
Location: orlando

Re: 10:1 compression on stock starter?

Postby terrible ted » Fri Sep 04, 2015 12:16 pm

When i ran a 350 10:1 with 202 fuelies shaved 30t i used a stock starter. Most problem come from small battery cables or bad connections.

User avatar
pontoon outlaw
Site Supporter - IV
Site Supporter - IV
Posts: 1663
Joined: Fri Dec 04, 2009 7:56 pm
Location: palm bay, ride in Cocoa

Re: 10:1 compression on stock starter?

Postby pontoon outlaw » Fri Sep 04, 2015 7:18 pm

:scratch: my first Cad had that comp ratio and I used a stock starter to turn it just fine, funny ting is that with my new Cad 507 when all was bolted up it dragged and wouldn't turn over freely I thought :slap: come to find out the ground location had fresh paint on it that I didn't shine off , so after a few brush strokes down to bare metal,,,,, problem solved :cheers: also might want to have battery tested for cranking amps, volts can read 14 but the cranking amps would be bad just a thought.....

User avatar
90chevy396
Southern Airboat Member
Posts: 242
Joined: Sun Mar 09, 2014 11:11 pm
Location: port saint john

Re: 10:1 compression on stock starter?

Postby 90chevy396 » Fri Sep 04, 2015 7:44 pm

hook your jumper cables both black and red clamps to the positive at battery and starter connection and try to start the engine and then if no change do the same for the negative and a known good ground. that will eliminate connection and wiring diameter possibilities.

if you want to upgrade to a gear reduction starter go to your local parts store and order a starter for a 98 Silverado with 5.7ltr and specify gear reduction and it comes with a lifetime warranty for less than $200.

look into the connections with which ever battery you have the most cranking amps first and then make sure its a quality battery not just your bottom shelf economy battery because of the reserve of the battery it will let you down at the most convenient time.
13' LASER W/455 BUICK DD SINGLE FRONT DOUBLE REAR WHIRL WIND PROPELLER

SWAMPHUNTER45
Site Supporter - III
Site Supporter - III
Posts: 2727
Joined: Thu Nov 21, 2013 11:38 am
Location: Naturecoast, Florida

Re: 10:1 compression on stock starter?

Postby SWAMPHUNTER45 » Fri Sep 04, 2015 7:59 pm

Curious if it could be a sum of several factors to include to much advance?

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Sat Sep 05, 2015 1:04 am

First off, I want to thank everyone for the replies. I cleaned the paint off the motor where I attach the ground cable but I didn't clean the paint off where the starter mounts. I would think the bolt threads would ground it but I may clean the paint off there, just to make sure. Tomorrow I plan on taking all the spark plugs out and see if that makes a difference. If so, then that may show that the starter just can't handle it..? :scratch: I'm also going to mess with the timing more. When I started it, I just wanted to be able to break the new cam in. I also have a mini gear reduction starter, but it doesn't line up right. When I install it the starter and flywheel gears are engaged. After looking at it, the bolt pattern is straight and I think I may need the staggered bolt pattern. Is there any chance that the new perko switch I installed could be causing a problem? I thought I read somewhere that they can have a high resistance..
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

speedymoe128
Southern Airboat Member
Posts: 39
Joined: Wed Jul 22, 2015 8:34 am
Location: northwest arkansas

Re: 10:1 compression on stock starter?

Postby speedymoe128 » Sat Sep 05, 2015 4:50 pm

a stock starter should start that motor with ease mine works just fine with that compression ratio if you think it is timing them unhook the wire to ur distributor and try that see if it turns over any better I am gonna say you prop have bad connection somewhere or a bad starter maybe

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Sat Sep 05, 2015 11:22 pm

Well I replaced the starter with a high torque starter that I got from a friend. It does the job. Still not as fast as I thought it would be but maybe it's just because this setup is new to me lol. I'm still going to try turning it over without the ignition wire and then maybe without the spark plugs to see the difference..
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0

SthrnStyle3
Southern Airboat Member
Posts: 510
Joined: Mon Apr 06, 2009 6:41 pm
Location: Sanford, FL

Re: 10:1 compression on stock starter?

Postby SthrnStyle3 » Tue Oct 20, 2015 6:09 pm

Just an update and maybe some info that may be helpful to someone. The starter I got from a friend crapped out. But I found a way to get a fairly cheap, decent gear reduction starter.. Go to any of the auto parts chain stores and ask for a 2004 Chevy Avalanche 2500 starter. The starter off that 8.1 L motor has a 4:1 gear reduction and a power rating of 1.4 kW. It has the staggered bolt pattern and will bolt right up to an old school smallblock. It was only around $90 and comes with a lifetime warranty.. Just an FYI!
12' aluminum hull, 350 sbc w/ flattop Pistons and camel hump heads, side by side seating w/ double in front, 2:1 gearbox and a 78" whirlwind whispertip 2.0


Return to “Airboat Tech”

Who is online

Users browsing this forum: Google Adsense [Bot], kwanjangnihm and 6 guests