BF75 cold blooded

Got an older carb'd BF75 that I brought back to life that is a bit cold blooded. Symptoms are when first put in the water it starts best by having the throttle up a bit and then you have to leave choke on for a few minutes. Run's great once warmed up. If out fishing and shut the motor off, if it sits for any time at all one has to hold the choke on for a short period or it doesn't want to stay running until you bring the RPM up a bit. The water temps where I am at is typically in the 60's.

I have pulled and cleaned the carbs. Obviously can't pull out the mixture screws without breaking them so the cleaning on these was spraying carb cleaner through all the ports. I did pull out everything possible and cleaned thoroughly. The carbs were surprising clean. I did not sync the carbs but looking at the adjustments, from the factory, the paint marks are all still in line and doesn't appear to ever have been adjusted. A dealer told me that he has found with the Honda carbs that they about need to be cleaned in an ultrasonic cleaner as even though all looks well you just can't get everything cleaned off. Also said to check Sync. Not sure I buy into this. I have turned wrenches all of my life and never had a problem with not being able to clean carbs with elbow grease but admittedly my experience with outboards has been limited to the BF50A and this 75. I suppose the idle mixture screws could be a problem but I don't think you can get them out without breaking them at least according to the manual.

Also made sure valves were set correctly.

Any thoughts on this? Is it possibly just the nature? I can by a sync manometer but I hate the thought of spending $100 for 1 use in several years. Also the engine runs well other than when cold so not convinced syncing would help.

I bought something like this about a hundred years ago for dialing in the Honda Goldwings (oldwings) I was messing with at the time. Now messing with the 40-90hp Honda outboards exclusively, I bet I've used it a hundred times now. Still works as good as it did 30 years ago. All I've done is to replace the cracked/split hoses one in a while, and bent up a hook from coat hanger wire to allow me to hang it. Worth it? Oh hell yes...... and yes, the adapters are the right size you need. Bottom carb is the master, you dial the others in to match that one.

https://www.amazon.com/Motoforti-Mo...=1658348849&sprefix=carb+sync,aps,170&sr=8-27

Have you checked the compression yet? They can get picky to start when it drops too far (below 100psi) but still run good when started. Generally the low compression is caused by a gooked up motor that is run mostly at idle without thermostats (think pontoon boat). That'll seriously carbon up the rings eventually, to the point they stick and won't seal well anymore. I've pulled motors like this down, cleared the stuck/sticky rings, and reassembled using only new gaskets. Starting compression = 80-90 psi, after thorough cleaning, 120 psi! Yes, I've brought a few of theses back to life as well!

Regarding those tamper proof idle screw locks. They're fastened with epoxy. It IS possible to heat them up and remove them, you just have to be darn careful about it. I was using a heavy duty soldering gun at first, but found a small propane torch to be much more effective. No prying! They have to be lifted straight up! Worst case is the screws are still available. Plan on replacing that o-ring they use to seal after getting them hot enough to remove that adapter. I'll admit to using a Dremel tool with cut off wheel to make my own slot too. It's not like you need to use them every day....

Thanks for the info Alan. The compression thing has been in the back of my head. I am almost hate to check it The number 4 cylinder was the one from previous posts that was filled with sand on the cooling side of things and I wondered if it got hot even though I was told it hadn't. I suppose worst case it is just a thing. Hopefully I can get through the rest of the summer before diving in if this is indeed the problem. Thanks for the gauges set info. I am a bit leery using cheap gauges versus manometer but for a one time use at 1/2 the price I can always verify they are reading correctly. Will report back

Gauges allow you to see all 4 cylinders at the same time. I find that MUCH easier than the single manometer.....

The manometer I speak of has four tubes. Same concept as the 4 gauges but here nor there.

Did a compression check and all 4 cylinders are at 120 PSI. When I first did it didn’t realize you have to open throttle all the way and scared me as compression read low. Anyways, I have a Honda OEM service manual for my model and it states the compression should be 213 +-14 at 300 rpm. This seems high to me. Compression ratio indicates 8.8 to 1 which is also different than some posts I have seen. Not sure if specs are that much different on the older engines.

Also, compression test was done cold.

Just did it warm and same numbers.

I'd forgotten about the type multi manometer you're thinking of....

A uniform 120 across all cylinders should run just fine in my experience. Yes, older motor for sure, but not ready for the boneyard yet! Regular use with a quality synthetic oil could even bring those numbers up 30 psi.

I think my focus might be on the fact you mentioned the chokes need to be closed for a "few minutes". Anything over just a couple of seconds would have most motors blubbering and blowing blue smoke in my experience.

Maybe time to address those uncleaned idle mixture screws? If you decide to do these, set them at 3 turns and they'll be pretty close.

The brass tubes that go up through the center of each carb has a tiny o-ring located at the top. It's critical to the idle system that o-ring seals well. If these are original, or getting long in tooth, I doubt seriously that's the case.

Have all of the fuel hoses been replaced yet? If these are all original they have to be pretty hard by now. Any wet spots anywhere indicating potentially cracked lines? WHat about the main fuel line coming from the tank. Is that reasonably fresh with a flexible fuel primer bulb? -Al

Thanks for the input Alan. I am going to get some print kits and get to the mixture screw and the other oring you mention. Had that all apart but didn’t change anything. Suppose I will try a carb sync as well. The motor runs to well to be a big issue.

I get it! When it's just running half way decent, knowing what it's capable of can be a curse! That last couple of percent can result in all the stuff we're talking about.

The results though, an easy starting motor that just sits there and hums while idling, is worth it to some of us! I have an older 90 (a near identical twin to your 75) on our pontoon boat. I went through that motor several years ago, and it's STILL running like it did when new. There are times I can't feel or hear anything but the pisser hitting the water. -Al

Thanks Alan. Going to figure it out. I am known at work to be tenacious as hell. I will report back.

Wanted to report back that after an ultrasonic cleaning and o-ring replacement on all carbs along with carb sync and idle air adjust the engine is much happier on the cold start front. For the sync, carbs were at factory settings from long ago. #3 carb was quite a bit off although suspect the issue was with idle air. After a struggle with one EPA lock using a soldering iron and then snapping the second one off a pencil torch became my friend. For anyone thinking about the torch idea if you ever get into this please use some sense on a few fronts but the biggest being be sure any fuel remains are cleared for obvious reasons.

YAY!

If you haven't already tried, that screw with the broken off EPA lock COULD have enough of a slot carved into it with a Dremel to be serviceable.

Doesn't take a lot. It's not like it's going to be used everyday....

Exactly what I did. In the garage at 12 midnight and the F bomb went off. Then I got enough of a slot to get it out and then a good slot to make it useable. No money spent.