Trigger Screw?????

[Floater49]

Last week I bought a boat with a 1974 115 inline 6 and the frustration level is rising. I bought the boat from a dealer, and they gave me the number for the previous owner. He informs me that the engine was professionally rebuilt last October. It was never "tuned" in the water since and therefore did not run right so it was traded in for a new boat.
I decided that I could do it. I printed off Clams' instructions for the link and sync and have tried to follow it. I thought it was straight forward, and maybe it is, but he uses a term "trigger screw". I can't see anything called that anywhere. All I can find is a "Idle Stop", Throttle Stop", and "Spark Adjust". There is another screw used for setting where the carbs open up after max advance is reached. But no Trigger screw.
Because of this, I can not get the idle and the "in gear" idle speed to be correct. It's either one or the other.
Pictures would be a great help!
Thanks for reading my first post/rant.

 

[hondon]

Re: Trigger Screw?????

The trigger screw is spark adjust.If you are convinced that you have achieved all ignition and timeining requirements you will now have to move to carbueration.What is the overall health of this engine?Compressoin numbers would be nice info to start.Keep in mind that you own an older engine and when this was enginered they had no concept of the fuels that they are now shovinig down our throats.They take a real toll on things like fuel pump diaphrams and pick up lines.

 

[Floater49]

Re: Trigger Screw?????

Ok, here is what I was told about the motor. #1 and 2 pistons and jugs were replaced due to an overheat caused by a bad impeller. Not sure if the owner had his terminology correct because I understood the block was modular and did not have individual jugs. Anyway, he told his mechanic to go through the rest of the engine because he wanted no issues once he got it onto the water. So the mech went through it. He replaced the 2 pistons and rings, decked the block and head, pulled the crank and checked it out, bearings, magnaflux for cracks, New timing belt, water pump, honed cylinders checked ring gaps and rest of pistons, replaced reed blocks and 2 reed sets, checked and adjusted shifter. I don't have compression #s for you yet. Although I am confident they are good.
I think I am understanding what I was thinking wrong before. I did do the steps as described, but I thought that the 4 degrees initial timing was going to stay set. But now I understand that it was just to get it running and then adjust from there to get a good idle and transition into forward. I followed the procedure and it works slick. Now it idles at around 800 in N and around 550-600 in gear. The timing at idle now is about 6-7 degrees btdc. lots of go when power is applied.
Do I pass the class?

 

[Chris1956]

Re: Trigger Screw?????

Floater, First of all that motor does not have a removeable head. It is also unlikely "the 1 and 2 jugs were replaced". More likely they were bored oversized, and more likely it was #1 and #3 cylinders. It is just the nature of the motor.

You should check the link and sync. With #2-6 plugs out and grounded to the block, and a timing light on #1, set the throttle using the fast idle lever until the distributor finger just touches the top carb lever arm. Now crank the motor with the starter and check the timing. It should be 4-6 degrees BTDC. If not set the timing to 2-6 BTDC, and loosen the two bolts on the dissy collar that controls the dissy finger, and turn it until it just touches the carb lever. tighten the bolts. Now set the throttle to WOT and crank it again. The timing should be 21 degrees BTDC. Adjust this with the Max Spark advance screw.

 

[Floater49]

Re: Trigger Screw?????

Chris
My collar is rotated all the way clockwise and it is just touching the throttle arm. It was at this point I had adjusted the idle screw to 4 degrees BTDC timing. I set the max advance with the spark adjust screw to acheive 21. I then went on to the carburetion. I guess my confusion came when I realized that if I set the idle screw to get the 4 BTDC earlier, and I use the same screw to get the 800 RPM, then the 4 Degrees was changed to get the 800 RPM. This brought it up to 6 degrees. Is that what is intended? The 21 obviously is not changed, so at least the motor should be safe at WOT. Does this sound right?
Thanks.

 

[emckelvy]

Re: Trigger Screw?????

Floater, you're correct in assuming that's for initial setup only. The motor's gonna end up with an idle timing that it 'likes' depending on what idle speed you set it at. But as long as the "primary pickup" is properly adjusted, you're OK.

BTW it sounds like they must have done a fairly good job with the rebuild, from what you described she's idling at a nice, slow speed and ain't too fussy!

HTH......ed

 

[Floater49]

Re: Trigger Screw?????

Update time!
Well, I put the boat into the water this afternoon after following the link and sync procedure as close as I could. I squeezed the primer bulb till it was hard then a bit more, lifted the warmup lever, hit the choke, and turned the key. It spun for 3 seconds and fired right up as smooth as can be. After a 3-4 minute warm-up at around 1500 RPM, I eased the Warm-up lever all the way down and enjoyed the sound of the 6 piston symphony. Easing the engine into gear, I idled away from the dock ever so smoothly, brought the revs up and it took off on a beautiful plane. After a few minutes, I stopped the boat and tried the "holeshot" test. The engine lept to life without a hesitation multiple times. I suspect that the prop is a bit shallow though. It topped out at 32 MPH on GPS. I suspect it is a 15 pitch prop on there. I also have a 19 and a 23. Not sure which I will try next. I Idled back to the dock and tried reverse. Both reverse and forward engage nearly completely silent. No grinding at all.
I couldn't be any more happy with this engine. A big thanks to Clams for his step by step on this one!!