new boat, some questions on 5.7 mercruiser

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

Hi, Just noticed your thread. I have a similar motor in a 19' 6" boat. I don't know exact weight but I know the boat & trailer weighed 3250 when I got it a few years ago. So maybe the boat weighs 2500 or 2600 I'd guess.
I have a 23 pitch Michigan wheel 3 blade aluminum prop and can spin my old pre vortec 350 to 4700 RPM at 58 mph on a pitot speedometer. My drive is a 1.47 ratio Alpha 1. And my motor only has the factory Rochester 750 on top. As far as I know it's all stock. I can tell you the idle is better and it pulls out of the hole better with the timing where it belongs. I'd definitely wait til you have the timing right before running it again.
I got a car GPS this winter so maybe I can report a gps speed if I ever get the boat in the water this year. Been too busy to boat!

When you get that motor set up right be very careful how you hit waves, your boat can launch right out of the water if you hit em with too much speed. If your boat gets air you need to pull back the throttle while the prop is out of the water. Then once the prop is just about to bite bring the throttle back on. Also if you are going to intentionally get it out of the water don't hit waves at an angle, the boat can come down crooked or sideways.
I think you have a 60 to 65 mph boat there.

thanks for the info! nice to have somewhat of a reference point. 60-65 seems about right from what ive read/gathered

i can assure you that i will be VERY careful when this boat is up and running smoothly

 

[Scott Danforth]

Re: new boat, some questions on 5.7 mercruiser

on the timing light, the inductive pickup goes on plug wire #1. there should be an arrow that says plug this side. the two alligator clips go to the battery.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

I don't need to put it in base timing mode I'm assuming because of being older model? Or look for pur/whi wires anyways? Going to try and get the serial of motor to try and narrow down details about motor

 

[Scott Danforth]

Re: new boat, some questions on 5.7 mercruiser

as far as your ignition system, not a clue what you have. could be mercruiser, could be aftermarket.

post a pic of the ignition system along with the engine serial number, etc. someone will be able to identify and comment. I agree, it would be wise to know what you have so you can use the right procedures.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

as far as your ignition system, not a clue what you have. could be mercruiser, could be aftermarket.

post a pic of the ignition system along with the engine serial number, etc. someone will be able to identify and comment. I agree, it would be wise to know what you have so you can use the right procedures.

i had this on my phone, didnt have time today to take any, planning to do timing/compression test tomorrow

 

[John_S]

Re: new boat, some questions on 5.7 mercruiser

i had this on my phone, didnt have time today to take any, planning to do timing/compression test tomorrow
View attachment 153717

Need a better pic of the module on the distributer, but it looks like Thunderbolt IV from what I can see. T4 does not have the purple/white wire, and does not have a base mode.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

Did compression test today, 120 all cylinders, spark plugs were black from preignition? Rich mix?

will post pics of them, guessing the timing is causing that? Or carb? any recommendations on replacement plugs? ngk?

It's a 1410 edelbrock carb ( 750cfm a bit much?)

thunder iv module

I got this code off block, mean anything -> 2m09131c34?

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser



pictures of spark plugs and ignition module

 

[Scott Danforth]

Re: new boat, some questions on 5.7 mercruiser

the plugs look wrong for the motor. they look too long. for reference, here is a picture of my plug that I checked

the TBIV is just like a standard ignition. there is no base-timing mode. at idle, you should be 6 degrees, however my guess is the engine isnt stock, so I would probably set it at 8

 

[TilliamWe]

Re: new boat, some questions on 5.7 mercruiser

the plugs look wrong for the motor. they look too long...

Good call. Based ont he picture in the very first post, this engine does NOT have Vortec heads. The plugs in his hand sure look like AC Delco MR 43LTS plugs to me. (They are for Vortec heads)

His heads should be using MR 43T.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

the plugs look wrong for the motor. they look too long. for reference, here is a picture of my plug that I checked

the TBIV is just like a standard ignition. there is no base-timing mode. at idle, you should be 6 degrees, however my guess is the engine isnt stock, so I would probably set it at 8

will be setting timing later this afternoon, will set a 8

spark plugs being too long, what problems would that cause? i will be sure to change them for the correct spark plugs this week

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

little question about timing, the timing marker shows a range of 14-0-8, with Before being on the larger range and after being the smaller range, the base timing should be set on which side of the zero? sorry if thats a dumb question, been trying to find the answer and keep getting confused

i decided to set at 8 degrees before (assumed because of btdc) just wanted to make sure, it was somewhere around 16 when i initially checked it :facepalm: brought the idle RPMs to around 625 and all sounds good, starts right up like a new car

i will be changing oil/gear lube and spark plugs this tuesday and doing another sea trial after i receive flame arrestor and will also take a fuel pressure gauge with me just to be sure.

random question, first sea trial, reverse was a little strange, went to move into gear and nothing, simply reved up in neutral, tried again and it engaged perfectly, any ideas on what to check?

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

Good call. Based ont he picture in the very first post, this engine does NOT have Vortec heads. The plugs in his hand sure look like AC Delco MR 43LTS plugs to me. (They are for Vortec heads)

His heads should be using MR 43T.

what kind of difference would having longer reach spark plugs make performance wise? condition of plugs?

i took them out again and they are mr43lts, will be changing them to your suggested mr43t tuesday

 

[John_S]

Re: new boat, some questions on 5.7 mercruiser

A 750 cfm vacuum 2ndary carb is commonly used by merc on most of the 350 SBC with 4brl carbs. The air valve will only open for what your engine needs. After you put the correct plugs in, check them to see if they are sooting up. If so, check your fuel pump site tube. If there is any fuel in it, you need a new fuel pump. If that is good, check if fuel is dribling at idle. Float setting may need adj, otherwise the carb needs some tuning.

8 degrees BTDC is correct. If you have an advance timing light, check it at 3500 or higher. Should be 30 or more degree BTDC.

 

[TilliamWe]

Re: new boat, some questions on 5.7 mercruiser

what kind of difference would having longer reach spark plugs make performance wise? condition of plugs?

i took them out again and they are mr43lts, will be changing them to your suggested mr43t tuesday

I don't know exactly what the longer plugs are doing inside your current heads. But they aren't supposed to be in there. The obviously rich condition could be a result of the plugs, but it is usually other things.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

hoping to take boat out this weekend, wanted to do quick oil/spark plug change

is part # 35866340q03 from quicksilver the correct replacement oil filter? found diff info, i have block mounted oil filter

 

[TilliamWe]

Re: new boat, some questions on 5.7 mercruiser

AC Delco PF25 ought to do it.

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

thanks!

 

[idleRelaxation]

Re: new boat, some questions on 5.7 mercruiser

swapped out spark plugs, went to change the oil and what do i find? grayish-brownish oil

boat is in miami so no winterizing cracked blocks/heads id assume, i suspect that the last owner might have used an automotive head gasket since the initial carb on the motor was also automotive (older mechanics i assume)

so i will be checking head gasket and removing the exhaust elbow and then manifolds to inspect, will post pictures of what i find if i cant deduce for myself

would there be any other specific places i should look for water intrusion that maybe some of my other symptoms have influenced/resulted from? oil on dipstick and when looking in thru valve covers looked fine

boat again turns on fine, idles fine, no smoke, restarts are a breeze, sounds very healthy, though thats not very telling

thanks in advance

 

[Scott Danforth]

Re: new boat, some questions on 5.7 mercruiser

have the heads pressure tested while they are out. check to see if you have an engine oil cooler. those can leak as well. generally water in oil is bad.