At my wits end

[chevysford]

Good Morning all, so I just registered here because I need a lot of help. I bought this old pontoon a couple of years ago. The guy who sold it to me hyped it up saying it has a “tower of power” on it. Over the years I’ve learned a bit about this engine and for the most part it used to run good. So what did I do? What any “smart” person would do, sink a bunch of money into a really old pontoon and try to make it new! So now the issue is I rebuilt the whole boat ( except toons), stuck her at the marina, used her for 6 months. Well she has ran like crap ever since. I found a cracked gas pickup tube fixed that. The boat runs great on muffs. Super strong. The second I put her in the water she can’t move to save her life and just dies. I rebuilt the carbs ( what I could) as some of the holes were JB’d. any help would be greatly appreciated. I am not sure of the year as I can’t find a number anywhere on this thing. Cowl has been painted but the front one said power trim and had I think grey and red lines. She is a 115hp. I also know how forums are and will tell you all in advance- I am an idiot so no hard feelings out of me. Ty

 

[Scott Danforth]

So what did you do on the motor?

How did you "rebuild" the carbs?

Did you do a link-n-sync?

What is the compression numbers?

What did you goober JB on (because that is never a repair)

Have you checked your fuel for contamination?

 

[chevysford]

Morning! I haven’t done anything on the engine at all. Ran some seafood through the carbs early on when I got her all back together.
Rebuilding the carbs was limited cause previous owner or whoever worked on it jb’d a bunch of stuff. After watching some YouTube vids, I think there are jets behind some of em. I just did gaskets and the floats. 2/3 had gas in em. Tried to soak her and blow air threw the rest. I did buy a compression tester but have not tested them yet. The fuel was definitely contaminated. That’s what let me find the bad pickup tube. So my order of what I did was, renovate boat, seafoam- ran great, marina, used it a little less than a yr, noticed speed and power decreasing, hard to start, pulled back out of marina, checked fuel and drained tank, cleaned carbs (attempted rebuild but couldn’t), did floats, replaced pickup tube in tank. Ran perfect on muffs, started fast and idleD good. Reved up as I thought it should, threw it back in water, started great, backed off trailer, died in launch about, restarted died about a quarter mile out. Ran good out launch and just kept losing more speed and power till it died for about 20 mins in middle of lake. Started back up, limped her to trailer at maybe 2 mphs, died 5x getting back. Got on trailer, brought her home. Checked all my work and found nothing. Put her on muffs and ran like a champ again. Brought back down to lake put in water did the exact same thing.

 

[dingbat]

Describe how it dies…..abruptly or like it’s running out of gas?

Does pumping the primer bulb have any effects as it’s dying?

Really need to check compression numbers to make sure you’re working on a “healthy” motor.

Quite possible you have a temperature related failure. Check to make sure you have spark good strong spark on all cylinders when it happens.

When was the last time you changed the water pump impeller?

 

[racerone]

Need to know when impeller was changed.----And it might just need low speed mixture screws opened 1/8th turn at a time to see if keeps running.

 

[airshot]

Another example of why you should test run and or a sea trial before purchase. Only bringing this up for others looking for a bargain boat, remember the old saying..." The most expensive boat you will ever own is the one you get for free" ....!!!

 

[merc850]

If you post the serial Nr. and some photos it would really help.

 

[Scott Danforth]

Morning! I haven’t done anything on the engine at all. Ran some seafood through the carbs early on when I got her all back together.
Rebuilding the carbs was limited cause previous owner or whoever worked on it jb’d a bunch of stuff. After watching some YouTube vids, I think there are jets behind some of em. I just did gaskets and the floats. 2/3 had gas in em. Tried to soak her and blow air threw the rest. I did buy a compression tester but have not tested them yet. The fuel was definitely contaminated. That’s what let me find the bad pickup tube. So my order of what I did was, renovate boat, seafoam- ran great, marina, used it a little less than a yr, noticed speed and power decreasing, hard to start, pulled back out of marina, checked fuel and drained tank, cleaned carbs (attempted rebuild but couldn’t), did floats, replaced pickup tube in tank. Ran perfect on muffs, started fast and idleD good. Reved up as I thought it should, threw it back in water, started great, backed off trailer, died in launch about, restarted died about a quarter mile out. Ran good out launch and just kept losing more speed and power till it died for about 20 mins in middle of lake. Started back up, limped her to trailer at maybe 2 mphs, died 5x getting back. Got on trailer, brought her home. Checked all my work and found nothing. Put her on muffs and ran like a champ again. Brought back down to lake put in water did the exact same thing.

fuel goes bad after 6 months.

seafoam is snake oil. there is no magic mechanic in a can

stop watching youfacetwittube videos. and read the factory manual. not a haynes, chilton, or seloc. however a factory Mercury manual. for ever 1 good video on facetube, there are 200,000 bad videos with bad information.

your motor will run on 2-3 cylinders. you could have 3 dead cylinders and not know it

first, do a compression test. PERIOD. put down the phone/keyboard/mouse and go do it now

post the numbers here.

if all are close to 130-150 psi, you are in good shape. if cylinder 3 is low, the motor suffered an overheat. if the top 2 cylinders are low, you were running lean and torched them

if the numbers come out good, go thru the complete fuel system. if you do not know how to rebuild carbs. pay someone

also, if you havent done a complete water pump service, do that. unless your compression numbers are low, then look for a new motor or find someone to rebuild your powerhead.

 

[chevysford]

Describe how it dies…..abruptly or like it’s running out of gas?

Does pumping the primer bulb have any effects as it’s dying?

Really need to check compression numbers to make sure you’re working on a “healthy” motor.

Quite possible you have a temperature related failure. Check to make sure you have spark good strong spark on all cylinders when it happens.

When was the last time you changed the water pump impeller?

It dies like it’s just bogging down. Not abruptly at all. Like it has decent speed and then starts slowing down, losing power then shuts off and won’t start again for like 15 minutes. Then it will start and run really bad with almost no power. The primer bulb had no effect as it was full of fuel. I’m debating moving the engine to a stand so I could work on it and not on a 6ft ladder.

 

[Gary H NC]

First thing I would do is the compression test!
I have had them run great on the hose but like crap under load...
At least rule that out before spending anything more on it!

Also from what you describe it sounds like it may be overheating.....
The water pump Impeller should be changed every 3 years max...
Good luck and welcome aboard.

 

[chevysford]

Need to know when impeller was changed.----And it might just need low speed mixture screws opened 1/8th turn at a time to see if keeps running.

Impeller has not been changed since I owned it and ran it, which was about a yr and a half

 

[chevysford]

First thing I would do is the compression test!
I have had them run great on the hose but like crap under load...
At least rule that out before spending anything more on it!

Also from what you describe it sounds like it may be overheating.....
The water pump Impeller should be changed every 3 years max...
Good luck and welcome aboard.

Did compression Test! 141,141,147,145,151,151

 

[chevysford]

fuel goes bad after 6 months.

seafoam is snake oil. there is no magic mechanic in a can

stop watching youfacetwittube videos. and read the factory manual. not a haynes, chilton, or seloc. however a factory Mercury manual. for ever 1 good video on facetube, there are 200,000 bad videos with bad information.

your motor will run on 2-3 cylinders. you could have 3 dead cylinders and not know it

first, do a compression test. PERIOD. put down the phone/keyboard/mouse and go do it now

post the numbers here.

if all are close to 130-150 psi, you are in good shape. if cylinder 3 is low, the motor suffered an overheat. if the top 2 cylinders are low, you were running lean and torched them

if the numbers come out good, go thru the complete fuel system. if you do not know how to rebuild carbs. pay someone

also, if you havent done a complete water pump service, do that. unless your compression numbers are low, then look for a new motor or find someone to rebuild your powerhead.

I did the compression test 141,141,147,145,151,151

 

[chevysford]

So update, I did the compression test. Here’s what I got. 141,141,147,145,151,151. I can’t find a sticker for it anywhere to get a year. Or even a stamp. The only number I could read was 971-8435. I’m gonna attach some pics hope it will help identify, but be aware it the cowl was painted so I only have the front part that wasn’t. I also added the spark plugs in top down order if that helps.

 

[chevysford]

Here are is a pic for the water pump disassembly

 

[racerone]

That is one of the models that needs a new impeller every 2 years.-----Also looks like it might have been run dry a few times.

 

[chevysford]

That is one of the models that needs a new impeller every 2 years.-----Also looks like it might have been run dry a few times.

Agree, replaced now

 

[chevysford]

Starting to wonder how this thing ran at all…

 

[Scott Danforth]

Compression is good. Now go thru the whole fuel system and replace the whole raw water pump

 

[Gary H NC]

Sounds like a fuel issue then..Compression numbers look ok.