100 horses 10 miles per hour

Allen 79 wrangler · Nov 12, 2011

I recently purchased a 1988 100 hp mercury 2+2 Serial #OB359296. It has a new switch box, fuel pump rebuild ,serviced carbs ,and ,new plugs. Motor has been timed and new plugs. Runs good sounds good 125 psi per cylinder but runs about like a ten horse power. I just inspected the reed valves and they are within spec. Is there anyone out there who can help out this very sad former Marine who just wants to get on the water. I was told something about a stator being an issue that this engine might have a high speed side that is tha culprit of my woes. Please help while there migth a chance to get on the water without freezing. Thank You

Allen 79 wrangler · Nov 12, 2011

Re: 100 horses 10 miles per hour

I just covered her up with plastic and will await parts and info to put her back together. I have the reed blocks out and can see light through them I was told that this could be my culprit. I was told by someone else it was a stator that did not function on the high end speeds ? I guess I will order reed valves before I put it back together. There are no chips or cracks and the gap between the reed block and the pedals is less than .020 . I am determined to get to the bottom of this and I am greatful for any help.

MercMan82 · Nov 12, 2011

Re: 100 horses 10 miles per hour

When you say "runs like a ten horse", do you mean it only goes as fast as a ten horse and that the motor doesn't bog down or miss when rev'd? Also, did you test the stator to see if it's a problem?

jeffersondodson561 · Nov 12, 2011

Re: 100 horses 10 miles per hour

How many rpms are you turning at 10 mph? Spun prop?

Allen 79 wrangler · Nov 12, 2011

Re: 100 horses 10 miles per hour

I dont think its a spun prop, I have been in that boat (pun intended). It will not hit the high rmps. I dont have a tachometer that works but I know Im not getting into the high rpm range. I was told that this motor has a two stage stator Im trying to confirm that fact? If that be the case I think it might be the problem.

MercMan82 · Nov 12, 2011

Re: 100 horses 10 miles per hour

Yes, yours has a low and high. This is a link to test your stator when you get the motor back together. http://cdielectronics.com/downloads/Mercury_DVA.pdf
Doubt it's your reeds btw if it idles ok although .02 is more than mercury allows. I believe it's .007. I think the bigger question is how are your reed stops?

Allen 79 wrangler · Nov 12, 2011

Re: 100 horses 10 miles per hour

I have 125 psi per cylinder. I had a professional mechanic set carbs and timing. It has a new switch box, rebuilt carbs, new plugs, and, fuel pump. It just won't wind up and go. I was thinking fuel delivery the last thing I checked was the reeds. Less than .020 gap between blocks and reed valves.

Allen 79 wrangler · Nov 12, 2011

Re: 100 horses 10 miles per hour

Ya think the stator could be the problem?

Allen 79 wrangler · Nov 12, 2011

Re: 100 horses 10 miles per hour

I dont know what a reed stop is?

j_martin · Nov 12, 2011

Re: 100 horses 10 miles per hour

If it idles, it ain't the reeds. Reed stop has no bearing on this, other than maybe being hard on the reeds. Not likely.

I got a doggy XR4 that now runs like a top........after I shot out the dozen or so bugs the "professional" mechanic put in it.

Just for grins and giggles, have you checked your throttle plates position at full throttle?

MercMan82 · Nov 12, 2011

Re: 100 horses 10 miles per hour

The reed stop is the thick metal piece that's mounted on top of the reed to restrict the maximum movement. I'm assuming, since you have taken it apart, you have a service manual. Again, mainly has to do with idle not wot. Anyway, I see that you have an assembly a retainer, not reed stop and unless something is majorly wrong it's not worth messing with. I agree with j_Martin, check the butterfly valves to actually see if they open fully and in sync.

CharlieB · Nov 13, 2011

Re: 100 horses 10 miles per hour

Your motor is commonly referred to as a 2 + 2 design. Only the upper two carbs have complete idle circuits and allow fuel flow it idle, the lower two only pass enough fuel to provide lubrication, but not enough for combustion.

As the throttle is opened an accelerator pump is activated to give a squirt of fuel to the lower cyls to assist their beginning combustion as airflow thru the carbs begins pulling in fuel.

Carb adjustment, accelerator pump adjustment, carb linkage synch, all are absolutely critical to the performance of this system.

As a prior posted pointed out, all ignition system test are well spelled out in the CDIElectronics Ignition Troubleshooting Guide, Follow their excellent directions to test your ignition system to ensure it is working properly.

Carb cleaning, sync and adjustment then becomes your priority to dial in the motor.

Check these links to see if your manual is still available.

http://1manual.com/Mercury manuals/Service_Manual_Index.html

http://forums.iboats.com/showthread.php?t=309079&p=2072211#post2072211

Study the fuel system, follow the directions, make sure everything is set letter perfect.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

I have set the the throttle plate position at closed and open. When I set them at the Wide open position I did get better performance. I'm thinking some "professionals" are best at removing you from the burden of deciding what to do with your money. Most however have been very helpful and I am grateful.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

I have a engine specific mercury shop manual. I have read and followed it carefully . I am grateful for the expirience that you guys are sharing with me. I know that this motor will run like a top soon. I just need to win the lottery so I can spend more time working with it.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

I did purchase one set of reeds that I will install because I already bent the retainer tab down. I will not however replace all of them because of the advice I have recieved from you fine men. I am gonna look deeper into this stator situation. I have discovered that mercury has put this stator in the obsolete pile. I have found it aftermarket. I wonder if mercury has had problems with this particular stator ? This motor is older and looks like it has very low hours.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

I just read more of the manual and discovered in the carbs there are plugs where there should be vent jets in other models and empty ports in my model. I have discoverd many problems with this engine as such. Every time I discover a shade tree mechanic error I think Ahhhh this is it. This does look like a problem that would keep the fuel from getting to where it needs to be. I guess I have enough info now to put some bolts back in the motor. Wish me luck so I don't make my own shade tree mechanic errors. I guess I won't because I don't have a shade tree.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

Thanks for the link CharlieB, I purchased this manual fiel from another site. With this link I now have the power to view the information on any computer. Very handy when your a commuter. I am at my girlfriends house and was able to discover my carb vent problem from here thanks to your link.

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

Thank you all for your help any ideas will be met with graditute. I will keep you posted on my progress.

jimbo_jwc · Nov 13, 2011

Re: 100 horses 10 miles per hour

Allen 79 wrangler said:
I just read more of the manual and discovered in the carbs there are plugs where there should be vent jets in other models and empty ports in my model. I have discoverd many problems with this engine as such. Every time I discover a shade tree mechanic error I think Ahhhh this is it. This does look like a problem that would keep the fuel from getting to where it needs to be. I guess I have enough info now to put some bolts back in the motor. Wish me luck so I don't make my own shade tree mechanic errors. I guess I won't because I don't have a shade tree.

Yes you do look under the boat unless it's in one you have ? Damm I hate it when I have to weed wip under my boat !

Allen 79 wrangler · Nov 13, 2011

Re: 100 horses 10 miles per hour

She is alive!!!!!! She is alive !!!!!!! I found a plug in every hole the should have been a vent. I took them out and headed to the river. Yeah baby she not only runs she runs good !!! Shot out of the hole and planed right up. I could not be happier. Thank you gentlemen for your advice hopefully this thread will help others.

100 horses 10 miles per hour

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