1990 Mercruiser 350 Inboard Issues

[Garretheck]

Ok new to the boating world but not unfamiliar with a sbc based engine.

I bought a boat(1990 Bluewater ProAm Skier) from a coworker this year with a known blown head gasket. Replaced both gaskets and it fired right up. Took it out to the lake and it started off the trailer and ran for 10-15 minutes. I shut it off to hook up a ski and it wouldn’t start. I suspected vapor lock but it wouldn’t start on starting fluid either. Is there anything obvious in missing here? I tried upping the idle on the carb but this doesn’t seem like a fuel issue since it won’t start on starting fluid either. The next day I fired it up on the trailer and it started first crank.

Thanks in advance!

 

[nola mike]

Could be flooding. What's your starting procedure? New gas? Did you check spark? Fuel/spark/compression/timing. One of them is off. Doesn't sound like compression or timing if it started the next day.
Also, welcome...

 

[Garretheck]

Starting procedure is turn the key. I was afraid of flooding it so I don't use the throttle. I did let it sit for a couple hours before trying to start it and still nothing, still could be flooded though. I did flush the fuel system when I got it and filled with non ethanol. Spark is good, timing is locked out at 30 degrees advance. Haven't checked compression since doing the head gaskets

 

[nola mike]

1. You'd better recheck your timing. I don't know your ignition system, but 30' at idle is way advanced.
2. To start a warm engine, you need to give it throttle. Put it in neutral and give it maybe ⅓ throttle. To clear a flooded engine, you give it full throttle and crank a bit. It's when you pump the throttle that gas enters the carb
3. Make sure the choke is opening when the engine is warm

 

[Scott06]

if it doesn't start or at least cough on starting fluid you don't have spark. Check your timing and use a spark gap tester to test the strength of the spark. I would go through the ignition components, ohm out the coil since its seems to not run after getting hot.
if it happens again when it wont start take the center coil wire off and ground it turn the engine over and check for spark. If you have it there check for spark at plugs to rule out cap and rotor, any short inside the distributor.
do you know what ignition you have ? Im assuming thunderbolt 4 but could be other.

to start there is no fast idle cam on a boat so usually pump the throttle a couple times to set the choke and pump some gas in then advance the throttle in nuetral to like the 10 oclock position. Pull the throttle back as it warms

 

[nola mike]

if it doesn't start or at least cough on starting fluid you don't have spark.

Unless it's flooded, or if his choke is stuck closed, or if his timing is actually 30', or if he's trying to start with the throttle completely closed. I'd bet he has spark. It's running, he shuts down, then it doesn't restart. It's running when hot, then not running when it's less hot.

 

[Garretheck]

Unless it's flooded, or if his choke is stuck closed, or if his timing is actually 30', or if he's trying to start with the throttle completely closed. I'd bet he has spark. It's running, he shuts down, then it doesn't restart. It's running when hot, then not running when it's less hot.

What should I be running timing at? Total is 30 with just mechanical advance. I'm not sure what springs are in there or what the advance is at idle. I set it at ~2500 rpm to make sure it was fully advanced. There is no vacuum advance

 

[nola mike]

What should I be running timing at? Total is 30 with just mechanical advance. I'm not sure what springs are in there or what the advance is at idle. I set it at ~2500 rpm to make sure it was fully advanced. There is no vacuum advance

I don't know what ignition system you have, they're all different. 30' at 2500 rpm is in the right ballpark, but you should be setting your timing at idle.

 

[Scott06]

What should I be running timing at? Total is 30 with just mechanical advance. I'm not sure what springs are in there or what the advance is at idle. I set it at ~2500 rpm to make sure it was fully advanced. There is no vacuum advance

yeah i figured 30 was total advance as i doubt it would run even ok if you were that far off. traditionally you set base or initial timing then as long as advance system ( mechanical or electronic) works you are ok. Its always good to verify total advance is ok, typical marine is 26-30 degrees and no marine distributors use vacuum advance as there is no part throttle high vacuum cruise like in a car.
A lot of tuners will just set total advance and let initial fall where it may.

while a stuck choke is possible i doubt you would run well and when ive had that happen to where the engine dies, plugs are so fouled they need to be cleaned before it will start again.
assuming it will happen again check for spark when it does. also pull some plugs to see what they look like. If it is flooded due to needle and seat issues or excessive fuel pressure plugs would be wet with gas and carbon black. These two simple checks will drive the trouble shooting. If your plugs are fouled cary a spare set and a socket to change them when u go out on the lake next.

may be worth jumpering out the kill switch as well If you are missing spark.