computer, oil injection,Thermostats removal on excel?

[bully]

Do you guys run thermostats. I live in South Carolina where the temps don't get that cold.

Any benefits other than not worrying about over heating?

I have an 89 excel yammi that I am considering removing the stats.

I am also considering removing the computer and oil injection.

Billy

[Markus]

Keep them in there. Yamaha's cooling system works really well without modifications. The cooling of the 60 degree 2.5 liter Mercury block is a different story.

As to the computer, removing it would allow you to run higher rpm, which tends to be a good thing. ;)

Yamaha's oil injection is very reliable, but if you want to run high rpm, remove it. (The 7500 rpm Pro-V 2.6 did not have oil injection)

[bully]

Markus

I have a surge problem at 4200-4300 rpm. Set the throttle at 4300 and she falls back to 3900rpm. Then she moves back up to 4300rpm and so on. It is not a miss like a bad plug. Acts more like a ghost is slowly moving the throttle back and forth. It will hold a certain rpm for about 15 seconds. Doesn't do it at WOT, but sometimes it wont turn up to its normal 5800rpm.

I tried another Throttle position sensor with no luck.

I really want to remove it. I have all the components off of a 200 yammi to make it a mechanical system. I just would like some experience with the situation. I realize I am going to have to make some brackets because the excel has a different intake than the 200.

Billy

[bully]

Another question


When I put on mechanical timing advance, what should I set the advance at?

Billy

[J Lamb]

sounds like a fuel restriction to me. Just fixed my dad's 89 excell cept his was a wide open surge. Would only rev to 4900-5100 and surge BAD. Replaced the fuel line from the tank to the transom (bulb). That took care of it. I think the line was getting closed somewhat. I would definately check the fuel system.

[Markus]

It fits quite nicely. If I remember it is only a couple of links that need to be custom made. In addition, the throttle cam does not fit great, but it works.

I am using the throttle arm from a 200, though, but you will need that anyway for mechanical advance.

Hydrotec sells a "de-computer kit" as well as a 200->225 kit, so they should know what you need. Hardcore marine is a great place for used Yamaha parts. I have links to both on my links page.

[Markus]

It sound like a fuel supply problem to me as well. Check for junk, restrictions and leaks.

[Markus]

IIRC, stock timing advance is 21 degrees. (I do not have the service manual here, but I am quite sure)

I have heard of people running 25-27 degrees, but your stock jetting may not allow that.

[bully]

I am pretty sure it is not a fuel restriction.

It only surges in the 4000 rpm range. If I go WOT, the surge is gone and I can get 5700-5800rpm, but sometimes it will only pull 5500 rpm which is exactly the rpm drop I see in the 4000rpm range.

If it were a fuel restriction, I would think it wouldn't pull 5700 rpm after it was surging in the 4000 rpm range just seconds before. When I have seen fuel restrictions in the past, the engine would pretty much die out once a certain rpm was reached. Not the case in my situation. I have talked to several mechanics that have told me to remove the computer.


Yesterday I pulled a mechanical timer base off of an old 200 and the timing advance/throttle lever. I installed it on my excel and got her running on the hose. I had to do some engineering to get the geometry correct. Now I have to fabricate a timing stop for full advance settings. I plan on setting the timing to 24 BTDC. The manual I have says 22 is the setting on the computer. I am almost finished with it, but it is raining.

If it turns out to be a fuel restriction, I will kick my self in the ass. Not all will be lost though. I can reverse everything I have done with out much problem. I really like the advance the computer gives on crankup anyways.


More details later.

[Ray Neudecker]

I would agree that it is a fuel restriction. Check the fuel pumps for a leak and carbs for a sticking needle. Most of the parts needed for the conversion come off the Pro V 200 such as linkage and cam. Will have to fabricate a throttle stop. Good Luck.

[bully]

Well I ran it today without the computer. I can only get 5600 rpm, but the surging is gone from what I can tell.

Question: Do I need to change the plugs to a resistor less type since the computer is gone?

Billy

[J Lamb]

Was it as cold in Charleston as it was in Columbia today? I had to stay in , nasty day. I'd keep the resistor plugs for the rest of your electronics. May have to check the heat range though.

[bully]

It was 43 and we were out in the boat. I felt like an idiot, but it was better than sitting at home doing nothing.

I think I may have a restriction anyway. I don't understand why I cant get 5800rpm any more.

Does the computer put more voltage to the power pack than the pulser coil does? Would that give me a weaker spark causing less power? I do notice that I am getting more smoke at idle now.

[Markus]

You do not need to change plugs. However, resistor less plugs are usually cheaper and less energy is lost in the plug, meaning more energy is available for the spark. You will not notice the performance difference, though.

[bully]

I looked up plug numbers for yammis on NGK's website.

They had BR9HS10's listed for the excel, which is what I have.

They had BR8HS10's listed for the 2.6 liter 225 20 inch shaft motor.

I have a 20 inch excel.

I think what they mean is the early 90's 225's that were 2.6 liter blocks.

Would it hurt if I ran a hotter plug like a B8 or BR8hs10?

What are the advantages to running a hotter plug or colder?

I found a slight amount of throttle not opening when at WOT. I adjusted it out, but I doubt the little bit will help.

Billy

[J Lamb]

I am by no means an outboard mechanic. My specialty is wheeled vehicles. I do know that by running a hotter plug you will increase your chance of detonation which is a bad thing in any engine. I wouldn't change the heat range if it were me. But my ProV 150 has been modified a little and I still run the br8hs-10 plugs. i'm not sure of the exact differences between the 2 motors other that timing,compression and ports as to why yours runs a colder plug.

[stray cat]

I had a bad surging problem on my Pro-V 150 that was traced to a restricted jet in the carbs,dont wast time finding the problem. Mine ended up killing the motor. Another website that you might try for info is boatset up.com, they have a Yamaha section that helped me a lot. I was also told that the connection on 80s Yamahas where the fuel lines connect to the motor have a problem with the inside of the connector flaking off on the inside and getting into the carbs, we think that is what happened to mine.:( Good luck with it.

[Markus]

If you have stock heads, NGK 8s will be fine, but 9s will give some extra insurance. The disadvantage of the 9s is that they will foul more.

To learn more about spark plugs, read the excellent article by Gordon Jennings on my links page (see below)

[bully]

Thanks Markus.

I ran the boat again on Saturday. She didn't surge at all again. I am hitting 5600 a little easier since I got the slack out of my linkage. I thing I lost some speed due to added weight. Remember, this is a saltwater fishing boat.

The 61 mph and 5800 rpm came when there was no 40lbs of anchor in the bow and cooler full of ice. I have also added a transom mount transducer that probably isn't helping and trim tabs that drag a touch at WOT. Oh, and a windshield.

I have hit 61 with the windshield though.

[Markus]

Bully, good luck with your Yamaha and let us know about your progress!

[bully]

Well Guys,

I think most of you were right. Threw her in for a ride yesterday, and the surge reappeared. I was really hoping the computer removal would fix her. I was just sick of pulling carbs off and cleaning them. I will have to flow test them again to see if there is any blockage behind the float seats. I pulled my fuel pumps and they were clean as a whistle. No leaks.

This one will have to wait until after xmas.

billy