$500 boat issues

xlrrp

Cadet
Joined
Sep 10, 2012
Messages
6
Hi,

First post on this awesome site. I am hoping for a bit of help as I am running out of ideas. I bought a $500 1978 Forumla Thunderbird F20 that has an OMC 240 (351w) with a Holley. It did not run and appears to not have in a few years, but the motor had been rebuilt. The paint is good and the freeze plugs look almost new. It was full of anti-freeze (San Juan fresh water cooling system).

I have been able to get it running by changing out the fuel, new spin on fuel filter, new plugs, points, rotor/cap, and rebuilt the carb (Holley 4160). It was dumping fuel into the intake and I discovered debris in the needle/seat that was keeping the float from completely stopping the fuel from entering the bowl. I fixed this.

No matter what I do, I cannot get it to idle below 1000rpm before it slowly starts sputtering and dies. Two things come to mind, this is the first carb I've ever rebuilt (Holley Renew kit) and also I timed it by ear.

So, I am going to use a timing light to set it at 10 degrees BTDC. Should have done that to begin with. I am also going to put the old power valve back into the Holley as I could not see the numbers and think the one in the kit may have been different. The kit was very generic and may not have been a marine kit after all (it's what Napa Auto sold me after I gave them the boat info and the numbers from the carb). Oh, and yesterday I put in an Ignitor II points eliminator kit, but the idle still does the same thing.

Am I missing anything here? Besides the idle and double checking my carb rebuild, any other ideas? One last thing, the intake appears to have some rust or corrosion inside that I saw when I removed the carb. Enough to concern me. Should I pull it and have it hot tanked to rule that out? I do see aftermarket intakes fairly cheap that could be another option.

When the motor is running, it has great oil pressure (50-60) and does not smoke from either the exhaust or the valve cover breather so that is a good thing.

Thanks and sorry for the long post..... Wait til I get the motor figured out and move on to the OMC 800 outdrive. That will generate many more questions. Btw, I am attempting not to put too much money into this five hundred dollar boat (yea, right) until I figure out if the motor/outdrive are going to work and do not have any major issues.

Thanks,

Chris
Washougal, Washington
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: $500 boat issues

The timing being off fits the idle issue as described.

Not sure how the needle and seat got debris in after a rebuild and filter change.

Power valves can dump fuel directly into the manifold anytime there is fuel in the carb bowl, so if it was not replaced during the rebuild, or the gasket was left out or not replaced then that needs to be done. The power valve rating would be a 3.5 - 6.5 or so. The kits usually come with an 8.5 I think. You can get the power valves separately as they are a tuning item.
 

emoney

Commander
Joined
Jul 19, 2010
Messages
2,551
Re: $500 boat issues

Yeah, my vote would be to set the timing the right way with a light and see what happens then. You might also want to have good long look at those fuel lines because picking up debris after a rebuild, it's gotta come from somewhere.

As for the intake, you're looking at it, but if it's got corrsion it's not going to "stop corroding", so you'd be better off rectifying that problem before it develops further.
 

xlrrp

Cadet
Joined
Sep 10, 2012
Messages
6
Re: $500 boat issues

Thanks for the replies. I guess I should have explained it better. I found the debris in the carb before rebuilding it and the float being stuck open was causing fuel to run into the intake. After the rebuild and cleaning, it stopped doing this. Yes, replaced the fuel line from the tank to the carb (tank to fuel filter, fuel filter to fuel pump, fuel pump to carb) and also emptied the 38 gal aluminum tank and looked inside it with a flash light, looked clean much to my surprise.

I will change the power valve to one rated for this motor instead of the one that was in the kit which may or may not have been correct. I will also start looking around for a place to hot tank and clean up my factory intake manifold. Still need to do a compression test so that's on the list too.

BTW, the reason the motor would not start was a combo of bad gas and the spark plugs that were in it were way too short. The new plugs were much longer and at first I thought I had the wrong ones so I tripple checked and the long ones were the right ones. Not sure why the previous owner put such short plugs in it and that makes me wonder what else is screwed up.

Thanks,

Chris

PS.... I haven't reached the point of parting the whole thing out to recover my money, but it's an option. Right now it's still fun to work on!
 

emoney

Commander
Joined
Jul 19, 2010
Messages
2,551
Re: $500 boat issues

Well, all that sounds pretty good, except for one thing. We have a rule around here that's pretty readily enforced: Pics or it didn't happen!

I'm disappointed in myself for not mentioning this earlier. Carry on. (oh and welcome to iboats!)
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: $500 boat issues

xl,

Set the timing then see how it acts. I would not go in after the power valve right now since you did change it. Get the timing and idle right then see if any other fuel related issues show up.
 

Maclin

Admiral
Joined
May 27, 2007
Messages
6,761
Re: $500 boat issues

... unless you were going to take the manifold off and all anyways, then might as well... Good luck!

still need pics though...I boat vicariously... :)
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: $500 boat issues

And set the points with a dwell meter and adust timing after you set the dwell.
 

floattest

Petty Officer 2nd Class
Joined
Jul 10, 2008
Messages
104
Re: $500 boat issues

that is a beautiful boat, I should know.

On your idle, is the old stock fuel filter still on it? Is it clean? When I got my boat the filter was a real mess, ended up putting a spin on fuel/water separator on it to replace the factory filter, the canister was rusted thru and the new filters are so much better than the old paper elements.



sweet-marie1.jpg
 

floattest

Petty Officer 2nd Class
Joined
Jul 10, 2008
Messages
104
Re: $500 boat issues

Chris,

I guess I wasn't suggesting that your fuel filter was the cause of the idle not getting down where it needs to be. You are on the right track with getting the timing right. If your ignition is right then idling issues will likely be the fault of the carb. The pros on here are very helpful and you'll get there. If your carb is right and all the adjustments have been checked you may test for vacuum leaks, which can be a cause of unstable idling.

You scored getting this boat for 500. I'm hoping you get it out on the river soon. If you get it idling right down around 600 you'll find the OMC is a dream to pilot. I got a lot of use out of mine this year.

FT
 

xlrrp

Cadet
Joined
Sep 10, 2012
Messages
6
Re: $500 boat issues

Ok, here's an update. Set the distributor timing (had to remove the distributor and move it a few teeth as the person who put it in didn't have it close). Then timed it to 10 degrees BTDC. The idle was about 1100 RPM's so I know the timing is not dead on, but it is closer than it was before. Still does the same thing. Dies below 1000 RPM.

SO...... Throw more money at it. The rebuild kit I bought at Napa was not for a Marine Holley 4160 EOJL 9510-CA, so I'm ordering the correct one. Wondered why I had to cut a bit of the gasket so the power valve would fit. Now I know. I am also buying a 2.5 power valve. The old one was unreadable, the one in the kit was an 8.5 and from what I see on the forums, older 351w's with this carb are mostly running 2.5's.

Getting new idle mixture screws and cork gaskets as the screws were cleaned with a wire wheel and I most likely should not have done that. They were in bad shape so I should have simply thrown them away. Last of all, I am replacing BOTH floats as I learned they can get fuel soaked and no longer work. Wow, should have just done the rebuild the right way to start with. Oh, and instead of using a pan of gas and compressed air to clean the carb, I'm going to buy a carb cleaner dip can and do it correctly.

Next question..... I either need to have my stock cast iron intake hot tanked to clean it up inside or replace it with an Edelbrock Performer intake (that would be my pick in aftermarket intakes). Would a 351w Edelbrock automotive intake work on an OMC 240 351w marine motor or is there something I'm not taking into account (water jackets, exhaust ports, or something like that)?

Last thought, when I first got thing running, the valve cover breather had lots of oil and hot exhaust blowing out of it. It was a mess. I gave up and tried it the next day and it was perfect. No blow by at all (new oil and at the correct level). I am guessing that the rings were stuck and by starting it they freed themselves???? It has zero blow by or hot exhaust coming from the breather cap now. BUT..... I bought a cheap compression tester and checked the #1 cylinder cold and only got 95psi. That concerns me as it seems low. I'm hoping that if it was really rebuilt a few years ago and never ran, then maybe the more I run it, the better the rings will seat...... Wishful thinking??

Thanks and please bear with me....... this is going to be a long process and once I hit around $1500, I'm done! I'll sell or part it out then if it is not ready to put in the water.
 

bruceb58

Supreme Mariner
Joined
Mar 5, 2006
Messages
30,454
Re: $500 boat issues

So what was the compression of the rest of the cylinders?
 

xlrrp

Cadet
Joined
Sep 10, 2012
Messages
6
Re: $500 boat issues

Update. Still waiting to perform compression test on all cylinders. The tester that I have fits fine in the #1 cylinder, but may not fit in the other cylinders due to clearance issues. I may need some type of adapter or a different guage.

Last weekend I changed the 6.5 power valuve to a 2.5. I also checked the primary float and slightly tweeked the level. I replaced both corroded air mixture screws with brand new ones. I then started it up and much to my surprise, it ran great. I was able to get it to idle just fine at 800 RPM and also adjusted the timing so it's set at 10 degrees BTDC. It ran perfect for 10-15 minutes....... THEN

The motor started missing and black smoke was coming out of the exhaust. It would no longer idle below 1000 RPM's. The temp gauge still stayed at 160-165 degrees and the oil pressure remained at 50psi or so. After a few minutes of this, I gave up and buttoned it up for the week.

My theory is that perhaps the old floats are "fuel logged" and no longer working as designed. Maybe they are sinking and allowing too much fuel into the engine causing it to run rich. Actually, I'm hoping that's what is going on as I'm out of ideas after that. I picked up two new side mounted Holley floats today and will install them this weekend.

Not sure if this is even possible, but my other thought is that something is cracked and maybe once the motor heats up it causes it to run rich??? Then again, it was running at normal temp for 10-15 minutes just fine before it started to act up. Back to the drawing board.

Chris
 

webrx

Seaman
Joined
Apr 29, 2009
Messages
69
Re: $500 boat issues

Not a marine inboard guy, but thought I would mention a couple things, first, recheck what you fixed - i.e. points, and condenser and position of distributor. Poinits could have slipped, condenser wire got cut by rotor, something was not tight and wiggled loose. If it ran perfect and then loaded up sounds like you had things right, but, don't forego double checking your work because "you know you set the points right" etc. I had one do similar (an outboard) and after a day of WTH, I went back to the points and found a broken condenser wire.

also, where did you set your mixture screws, and did you adjust them after starting the motor? When the motor was running bad, did you pull plug wires to see if one made no difference? could have a plug wire or coil breaking down when it gets hot. missing and black smoke (assuming it smells like gas and not oil) indicate a rich condition, or a cylinder not firing.

Just some thoughts

Dave
 

xlrrp

Cadet
Joined
Sep 10, 2012
Messages
6
Re: $500 boat issues

Hi,

Haven't had much time to work on the boat. So, newest update and need some advice for a major screw up I made. Can't believe I did it actually.

I have not checked the other cylinders with a compression tester as the one I have will not fit (threads will, but clearance is too tight due to the manifolds). When I get a different tester I will check compression on all cylinders and post the results.

In the meantime I rebuilt the Holley carb with the correct renew kit. I also replaced both floats as I suspected that they may have been soaked and no longer working correctly. It was slightly raining today when I put the carb back on and fired it up. Ran awesome for a short time then MY SCREWUP happened.

I did not connect the electric choke wire well and it came lose and grounded against the intake manifold. I actually saw it spark so I know that's what happened (good thing the boat didn't catch fire). Now I have no power to the starter at all. Also, with the key in the on position I have no juice to the coil. I should have taken more time and ensured that the wire was on good. On the plus side, the engine was running great for about four minutes.

I looked and cannot find a blown fuse. Anyone have any idea what the problem could be. I oviously shorted something out, just can't figure out what.

Seaman, sorry for the delayed reply. The points were replaced with an electronic ignition so I know that's not the issue. The mixture screws were seated and backed out 1.5 turns at first and then adjusted as the motor idled. I did not pull any plug wires to see if one cylinder was no firing, but plan to pull the plugs and look at them. Also, it was running rich and smelled like fuel before the carb was rebuilt. I'm hoping that once I figure out why I have no juice to the starter and get it running again, the engine will run fine with the new floats in the carb.

Thanks for all the advice on this.

Chris
 
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