Logo
FULL SITE MENU

Timing Issue 1987 5.7 L model 260hp merc

87concord

87concord

Regular Contributor
so this may sound dumb but i have had my boat three years and never thought to check the timiming until yesterday. it is an 87 model 260hp 5.7L and when we checked it was showing to be at 14 degrees BTDC. I always thought that 8 to 10 degrees BTDC was more acceptable. I retarded to 10 degrees just to be on the safe side. I was also told i may gain a little top end power by retarding 4 degrees but havent had it in the water to see what it will do. any thoughts or suggestions would be appreciated. should i have left it alone or is tinkering with timing a normal practice?
 
Re: Timing Issue 87 model 260hp merc

if it hasn't stopped running in three years, I'd say there wasn't anything wrong with it. The more critical timing parameter to check is full advance. Get that dialed in and make sure it starts ok, both hot and cold, and you'll be fine.

If it is the thunderbolt system, it is a "set it once and check it" annually type of deal.
 
Re: Timing Issue 87 model 260hp merc

it is thunderbolt. what should it read at full advance? i have heard that advancing the timing can give more bottom end power but kill the top like end, it has always felt it could wind a little tighter but something is holding it back. im running a 21p laser II turning 4300 at WOT
 
Re: Timing Issue 87 model 260hp merc

What manual you working out of ?

Listen you have not tuned or looked at the plugs on this boat all the time you have the boat ?

Drive oil ? Motor oil ? Impeller change ? Anything else you have not done ?

Wot was in the recommendation that is 4200-4600
 
Re: Timing Issue 87 model 260hp merc

you should get the factor service manual.

A quick glance shows 8 deg BTC at idle with another 24 degrees (+/-2) in by 3800 rpm. The nominal "advance" built into the module is stamped onto its mounting plate.

I think whoever told you the "timing advance story" has confused ignition timing with camshaft timing but that's a different thread.
 
Re: Timing Issue 87 model 260hp merc

chief,

i have the oil and drive oil changed yearly when winterizing, the plugs where replaced when i bought it. i was just wondering what the time was set at so i checked it to see, im not an idiot dont assume that i am one. im just tinkering for the sake of it. Isnt that how people learn about things, by asking questions and tinkering?
 
Last edited:
Re: Timing Issue 87 model 260hp merc

So your doing what has to be done to make sure the boat runs good and make it last.

Good for you doing the right thing.
 
Re: Timing Issue 87 model 260hp merc

its a thunderbolt iv, its a mechanical advance, like i said it runs good but feels like it could run better. im building a new vortec engine as we speak so i really dont know why i care about this old one, i guess i just want to get the most out of it while im using it, im a speed freak so i guess the smallest things drive me nuts, anything to milk that extra mph, im shooting for mid to high 60's with new engine
 
Re: Timing Issue 87 model 260hp merc

im sure you guys have figured it out but thats my boat in my avatar. it aint much but damn i love it, god bless the small block
 
Re: Timing Issue 87 model 260hp merc

TB IV is all electric, no mechanical advance. TB IV has 'male' terminal for the spark plug leads & coil.
 
Re: Timing Issue 87 model 260hp merc

260 HP on a boat that looks to be in the 22 to 24 ft range? 21 P and 4300 RPM... That's about all you'll get.

Re: "I'm not an idiot"... Don't think anyone thought you are, however, many of us respond to posts with an eye to the fact that not only the original poster reads these posts, but others who are less competent who are looking for answers. Soooo, apologies in advance if you think anyone posting responses is talking down to you.
 
Re: Timing Issue 87 model 260hp merc

You'll find that TB IV is one of the best HEI systems around.

The only issue with them nowadays is finding a module when you need one.
 
Re: Timing Issue 87 model 260hp merc

you are right makomark my module went out on my thunderbolt lV. a new one was 494 and some change changed over to a delco remey a easy fix. boat runs very well now!
 
Back
Top