Won't go Full throttle at first. Runs fine after a Bit. Timing issue?

[hagadonecp]

I have a 1986 75hp Mercury outboard (4cly). Just to Start, I'm not really familiar with boat motors. I can do the basics, but my brother in-law usually helps with indepth things. I had some starting issues a few weeks ago and we replaced the Stator (cracked), Flywheel (center was broke), and the Trigger (just because we were in that far). The boat started right up. It ran good with the ear muffs on and you could give it full throttle and it will go. I've taken it out 2 times since the fixes and when we first start it, it won't go full throttle. It will only go around 7mph and when you give it full throttle it seems to skip & buck a little but it won't rev up and go. It bogs down some, but doesn't usually stall. It will do this for a while. Usually we give up and fish for a couple hours & try it again. It will do it again, but after working on it 10 more minutes it all of sudden will kick in and go. It will run fine for the rest of the day. No idea of the issue. My brother-in-law thinks it's the timing, since we replaced those 3 parts, but he's not comfortable doing that. He's not really a fan of the outboards. Before i take it somewhere, i was wondering if it was the timing or if it might be flooding, air in the gas line (vapor lock), or something small. The Carbs were redone at the end of last year also. Runs great in Neutral & once it finally kicks in. Any thoughts?

Thanks,
Curtis

 

[fastjeff]

Sounds like a bad switch box, but try this first: Open each idle mixture screw OUT 1/2 turn (CCW). You might simply have a lean bogging problem caused by ethanol fuel.

Jeff

 

[Texasmark]

On timing, my 90 triple is spec'd at about 0 at idle but 20 BTDC at WOT. I know it's not a classic like yours (had a '74 85) but the point here is at WOT 2 strokes like to be lead. Did you check you timing when repairs were finished?

I had a problem for a long time with my engine. It usually sits for quite awhile as I don't get out that often any more. Upon launching, it was really thirsty initially in getting fuel to the engine for starting.....I blame that on seldom usage.

I'd let it run while putting up the trailer and back in the boat and motor out to the end of the no wake zone and punch it. Every single time it would cough and lurch and vibrate and miss and all that bad stuff until I got it up on plane the first time. Then all was well the rest of the day. Started immediately, punch it and it took everything you gave it, ran out to 56-5800 rpms and sang like a bird.

After 10 years of not touching the carbs, one day I did. On this engine (2B2 carbs) the high speed jet is a brass threaded plug, hole in it, in the bottom of the bowl. Upon removing the 3 bowls inspection revealed a spotless casting. Sea Foam had done it's deed. However, before putting them aside, I blasted all 3 (jets) with compressed air from both directions. Carb 1 and 2 yielded no foreign material. However when I hit #3 a piece of black something was dislodged and I saw it. Seemed to be a piece of fuel line that had deteriorated (engine is 12 yrs old). Put it all back together and no more problem on the first hole shot. Just a thought.

Tend to agree with Jeff on opening the low speed jets, if no internal carb problems. But with it running fine the rest of the day it makes me wonder. Some of the guys on other sites do this to check their low speed adjustment. With the boat still locked on the trailer like when transporting, transom well in the water (getting the water pump covered) they would start the engine, let it warm and then put it in F and goose it. They would open the low speed jets as necessary until the engine would take the throttle and not stall. I like that approach. You are at the ramp, not bouncing up and down the lake handing over the transom, trying to push the tow vehicle and trailer up the ramp is surely more stress than the hole shot. Something to think about.

Best I can do,
Mark