varying power levels

[loukel]

I have a 1983 force 85 horse that will run W.O.T. at 25 M.P.H. and then occasionally will accelerate to 40 M.P.H. Compression is 130 on all three Cyls. Problem is getting worse <br />Fuel pump gaskets and diaphram replaced. Fresh gas allways used with wally word Synthetic oil at 50/1 ratio. plug replacement does not have any impact. Any help appreciated . [/LIST]

 

[The Marine Doctor]

Re: varying power levels

Remove the head and check the cyl wall, if they are smooth the engine is in need of a rebuild. The air fuel mixture will be pushing past the rings.<br /><br />TMD

 

[JB]

Re: varying power levels

I think you are running on 2 cylinders most of the time, Loukel. It is when the third cylinder cuts in that you take off. If you are getting 130psi on all cylinders I don't see evidence of blow-by.<br /><br />It is pretty rare that I disagree with TMD. He is, after all, a real guru on outboards.<br /><br />First step is to determine if that is the case, then whether the dead cylinder is missing fuel or spark.<br /><br />Crank it up on the muffs, at idle. Short out each spark plug (CAREFUL ). Idle speed should drop in each case. If it doesn't drop on one, that cylinder is not making power. Test for spark.<br /><br />If you have good spark to a dead cylinder, spray some premix fuel into that carb. If the idle immediately goes up that carb is at fault, overhaul it.<br /><br />If none of the above tests reveal anything, inspect all of your ignition wiring for shorting to the block or to the cover.<br /><br />Let us know what you find, and good luck.

 

[The Marine Doctor]

Re: varying power levels

JB, the only reason I suggested the blow by is because I ran into it this year.<br /><br />85hp Force 1989 blew 125 on all cyl's. NOTHING we did could make it go over 3800 RPM. Trust me I mean NOTHING. And yet on occasion it would up and take off all on its own.<br /><br />It was not until we tore the engine down that we found broken rings on #1 and #3 cyl just floating in the piston. They did not appear to do any damage to the engine other than make the engine lose power. So we figured the engine just plain wore out.<br /><br />Do not worry I would not post of this kind of nature unless I had seen it before.<br /><br />I do not think an 85hp engine would make it to 25mph on 2 cyls.<br /><br />TMD

 

[force01]

Re: varying power levels

loukel<br /><br />i had a customer with your exact complaint. so we put the engine in a tank on our dyno for two hours at varying rpms couldnt find the problem, so we sent the customer back to the lake sure enough <br />it was back. so this time i went to the lake with tools ,with a inductive timing light hooked to the ign wires one at a time i drove around until i found the problem it would drop one cylinder then recover . so i would try this test i think you will find your problem. check both ign and carburetion before you tear down this motor. i have seen similiar problems that the marine doctor<br /> is speaking about, but exhaust all external posibilities before rebuilding the motor good luck bret If you need further assistance please email me @ forcepower01@yahoo.com. thanks,Bret

 

[JB]

Re: varying power levels

Hi, Loukel.<br /><br />If you need further advice post it here.<br /><br />We do not allow businesses or freelancers to post links or Emails in search of business, and just to keep TMD and Force01 from being misunderstood,let them answer your questions here.<br /><br />TMD and Force01: You are both very valued advisers here and we respect your motives. Please don't seek to divert help requests into private conversations. Our members don't learn anything from interrupted threads. Please don't post your Email addresses or put them in your signatures.<br /><br />Thanks for your continuing help and cooperation.