75hp Force Bogging at high RPM

[plaidpotato]

I'm a new boater, and I know nothing of boats, I'm much more farmiliar with automotive systems.<br />I recently purchased a 96 16' bayliner with a 75hp<br />force outboard, I'm assuming its about the same year model. The engine seems to run fine after warmed up, idles well, and even runns well up past 3/4 of the throttle, on full throttle it boggs down and if held at full throttle it dies. The engine restarts right away, but this concerns me, the owner said he left a full tank of gas in the tank for nearly a year, with no fuel stabalizer or anything like that. He drained as much as possible out of the tank and put about 7 gallons with oil in before we went and ran it.<br />I want to check the compression first to make sure the engine isnt seriously damaged, how exactly do i check compression, can I use a standard automotve comp guage?<br />Can I use automotive grade decarb spray in the carb to try and blow it out?<br /><br />Thanks for the info

 

[roscoe]

Re: 75hp Force Bogging at high RPM

Welcome to iboats stripedpotato. <br /><br />Yes, use an automotive compression gauge.<br /><br />If possible, warm up the engine.<br />Trip the kill switch to the "stop" position.<br />Remove both sparkplugs.<br />Set throttle control to FULL throttle.<br />Connect compression gauge.<br />Crank the engine 4-5 revolutions.<br />Observe reading.<br />Repeat on other cylinder.<br /><br />The 75 was made from '96-'99.<br /><br />I suspect your carb is gunked up. Good idea to clean her up and see if that solves the problem.<br /><br />Do not use regular carb cleaner in a 2 cycle outboard. They can burn up your motor and leave the metal surfaces unprotected.<br /><br />Get some Seafoam Deep Creep, Mercury Powertune, or Yamaha Ringfree, if you want to decarbon your motor. Good idea to do it too. These are made for 2 strokes and contain oil to keep the engine lubricated. <br /><br />See Decarb posts in the FAQ forum for more details.<br /><br />Spraying a decarb solution through the carb will not clean the carb. Only a disassemble and cleaning, will get the jets cleaned out. So get a carb rebuild kit from a Mercury dealer and have at it. Should be part number 820576A1

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

Thanks for the info, I'm glad you told me not to use the automotive carb cleaner, I was about to do that. Do you have any idea of a national retailer that might carry the sea foam deep creep, so I could pick some up locally?<br /><br />Thanks

 

[roscoe]

Re: 75hp Force Bogging at high RPM

NAPA carries the Seafoam and the Seafoam Deep Creep.<br />Maybe not every location has it in stock, but they can get it for you.<br /><br />Mercury, Yamaha, or Evinrude dealer will have similar product with their name on it.

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

well, i found out today from my local repair shop that my worst fears have come true, the engine has low compression on one cylinder and that is the cause of my problem. They are offering me a rebuild or complete powerhead replacement for anywhere from $3500 to $5000.<br />I didnt pay that much for the complete boat, and it doesnt seem any cheaper to replace the outboard all together.<br />any suggestions or advice?

 

[roscoe]

Re: 75hp Force Bogging at high RPM

A rebuild may be as cheap as $1500, no way of knowing till you open it up though.<br /><br />$2000-2300 will get a powerhead shipped to your door.<br /><br /> http://www.boatmotors.com/motorpart...year=1996&state=wi&zip=54451&hp=75&disp=&cyl= <br /><br />$1500-3000 to install it sounds outrageous to me.<br /><br />I would shop around at a few different mechanics/shops.<br /><br />Or you could buy a 2005 Merc Optimax delivered for about $4000.<br /><br /> http://www.boatmotors.com/motorparts/index.cgi?pid=4937&flag=2 <br /><br />There is always the option of finding a used motor for a lot less, if you are patient.

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

yeah, I'm definately trying to shop around.<br />does anyone have any experience with <br />TMS Marine Parts<br /> http://www.tenkillermarine.com/boatparts/powerhead.asp <br />they claim to rebuild my powerhead for $1295 including shipping both ways and give a lifetime warranty with it, it really sounds too good to be true, if this is possible why wouldnt my local service center offer it more reasonably?<br />just curious to know anyones opinions or personal experience with these guys

 

[RRitt]

Re: 75hp Force Bogging at high RPM

$1295 sounds reasonable. <br />powerhead kits not purchased from mercury are $450ish. http://www.powerheadkit.com/ <br /><br />they only go into the thousands when mercury gets a cut of the profit.<br /><br />The question is what does he do if your head or block is cracked? If his price is based on good metal and he's got enough Force experience to feel 100% confident in his rebuilds then he's making a healthy enough profit to cover his warranty and shipping.

 

[roscoe]

Re: 75hp Force Bogging at high RPM

He's been around a while.<br />I've bought parts from him, but thats all I can tell you about him.<br /><br />I', sur e the warranty covers his workmanship and defective parts. But not owner error, like no oil in fuel, or overheat, etc.

 

[b.gagnon]

Re: 75hp Force Bogging at high RPM

What were the psi readings? It could be a stuck ring that needs a de-carb...

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

i'm not sure exactly what the psi readings were, I will find out from the repair shop that checked it.<br />I talked to an independant mechanic this weekend and he also suggested that the rings may be stuck and to soak the spark plug holes with seafoam repeatedly for 3-4 days and then take it the lake to run it. Makes sense to me because seems like if it were a broken ring or worse I would hear something rattling in the engine or something like that, is that not the case?

 

[b.gagnon]

Re: 75hp Force Bogging at high RPM

On a three cylinder motor when one cylinder goes the motor usually does not idle well.<br />Did your overheat alarm ever go on? I am just hoping the best for you!

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

it idles wonderfully, and starts easy every time, I never heard the overheat alarm, not sure what it sounds like, being a newbie, but it had this problem bogging down before i bought it when the owner demoed it for me, so I dont know if it ever overheated before I got it.<br />Is there no way to know the cause of low compression without doing a teardown?

 

[roscoe]

Re: 75hp Force Bogging at high RPM

"low compression" could be bad, or not so bad.<br />How low?<br />Could just be a blown head gasket.<br /><br />You can look inside the sparkplug hole and look for damage to the piston, and examine the sparkplugs itself.<br /><br />You can also pull the head off and examine the head gasket and its mating surfaces.<br /><br />If it was mine, I would examine the sparkplugs.<br />Then check compression myself, write down the readings.<br />Then do a serious decarb.<br />Recheck compression.<br />Then if readings are still low, remove head and examine.<br /><br />Let's see, on one hand you have the cost of the Seafoam deep creeep, the compression gauge, and a gasket = $65 verses $2000-$5000 on the other hand.

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

the compression readings are 85-135-135, the local repair shop tells me that it is very unlikly that the rings have stuck closed due to carbon and caused that much of a drop in compression, i pulled the plugs before taking it in and only saw black on the tips of the plugs, the repair shop told me that they didnt notice any aluminum on the spark plug which would be a sign of something broken inside. He said they could remove the head and inspect for an additional hour of labor, I think i should try the decarb first

 

[roscoe]

Re: 75hp Force Bogging at high RPM

85 is awful low.<br />But decarb first, its cheap.<br /><br />Could still be a blown head gasket, or a broken ring that did not do any major internal damage.<br />Don't give up hope yet.

 

[hamburgerman]

Re: 75hp Force Bogging at high RPM

My low compression was a head gasket 23.50 and good as new if you take off the head you can see if there is any scoring from the rings. I had an old motor once with bad scoring and the more it ran the better it got SUPRISE

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

thanks for all the advice<br />I found an independant mechanic that is going to remove the head, for a lot less than the local dealer service, and ispect the engine and let me know what is going on. Hopefully it wont be too bad.<br />Keep your fingers crossed for me....lol

 

[Kahrmar3912]

Re: 75hp Force Bogging at high RPM

Fingers bcrossed

 

[plaidpotato]

Re: 75hp Force Bogging at high RPM

well, the mechanic pulled off the head on my motor and tells me that the number 1 cylinder is so worn out, its not even rebuildable, that my only option would be to replace the power head, but recommends that replacing the engine with a good quality used unit would be more cost effective.<br />I'm curious to know what the max HP my boat is rated for, I've been told that it is on an ID plate somewhere but I cant find it. Its a 1996 Bayliner Capri 16' open bow, any one know or know where I can find that plate to find out?