Mercruiser 2.5 help

[Leveecius]

I'm lost and need help. I'm a semi mechanic so I'm very mechanical savy, but my Mercruiser 2.5 is giving me a migraine and I can't figure it out. I don't know why, but the boat runs flawlessly at an idle or even higher rpms with no load, as soon as the load gets on the engine it will run about 10 seconds and die out like it's starving for fuel, and even once it starts dying it won't catch itself. Both jets seem to be working fine. Not sure if the choke is working. I'm not sure how to test it. Odd part is, I had it in the water a few days ago and it ran fine, no issues whatsoever. I took on a rope on the prop and it got warm, not overheated but warm and it hasn't ran right since. Doesn't get hot after clearing it and compression is good across the board.. what is going on with my boat?

 

[Bondo]

as soon as the load gets on the engine it will run about 10 seconds and die out like it's starving for fuel, and even once it starts dying it won't catch itself.

Ayuh,..... Welcome Aboard,...... It sure acts like a lack of fuel,......

Don't suppose you've got a canister style fuel filter on it, do ya,..??

If by chance ones been added, check it's contents for anything but clean fresh gasoline,.....

 

[Leveecius]

Thanks for your response. I'll be checking this often! I know it has a screen canister in the carb, and it has an inline added before the mechanical lift. I have drained the tank completely and put new fuel in (thinking water in the tank), and it has a new inline filter. The screen in carb is clean. It looks like the inline keeps draining and never stays filled. But the inline never filled before the issues came tho so I don't think that's an issue.

 

[achris]

You have an air leak in the fuel system somewhere (before the fuel pump, or on the inlet side of the pump)....

 

[Leveecius]

Could a broken fuel cap seal be a cause?

 

[Bondo]

Could a broken fuel cap seal be a cause?

Naw,.... An air leak on the suction side,.....

Dip tube, elbow at the outlet, fuel lines, or filters, up to the fuel pump,.....

 

[Leveecius]

Naw,.... An air leak on the suction side,.....

Dip tube, elbow at the outlet, fuel lines, or filters, up to the fuel pump,.....

I guess my only question on that is, can a dip tube go bad between tank fills in less than 24 hours? As that is quite literally the only thing I haven't touched. When I drained the tank, I just the existing fuel line and just gravity drained the fuel and changed the inline filter afterwards. Sorry for my ignorance, I'm just lost at how this just magically started up from no previous signs of issues.

 

[Rick Stephens]

Didn't the older mechanical pumps on the 4 cylinder motors have a built in filter with separator bowl?

 

[Leveecius]

Didn't the older mechanical pumps on the 4 cylinder motors have a built in filter with separator bowl?

No clue! It looks like an inverted fuel water separator bowl to me with a single strap holding it down! If it is a filter in there, I wouldn't know!

 

[Leveecius]

Sorry, I just noticed I didn't put it up there, but I'm a semi mechanic and new to boats (I know, sorry for the pain of banging your heads on the wall). So I am kinda lacking things that might even be simple knowledge when it comes to boats.

 

[Scott06]

No clue! It looks like an inverted fuel water separator bowl to me with a single strap holding it down! If it is a filter in there, I wouldn't know!

Yes there is a filter in there would remove the strap and check it out

 

[Leveecius]

Yes there is a filter in there would remove the strap and check it out

Will definitely do! Thanks!

 

[Rick Stephens]

Will definitely do! Thanks!

Take pictures and post of what you find

 

[achris]

..I guess my only question on that is, can a dip tube go bad between tank fills in less than 24 hours?....

For everything that fails, just before it did, it was working fine... So yes, things fail without giving written notice 3 weeks in advance.

Chris........

 

[Leveecius]

Ok, I didn't get a chance to jump on it yesterday but got to it today. I pulled apart the main filter, and it looked clean and new. Although the gasket looked off. I also found sediment at the bottom of the housing on the pump itself (I have a low pressure system apparently). I pulled apart the carb intake fuel line and yanked the screen out if it and it had what looked to be a mud trail collected at the bottom. Pulled all lines and flushed the system. Cleaned the screen and put it all back together.

When looking at it, with the throttle at idle the choke plate was wide open. Well, that's not right, so I did some research and found how to adjust the choke. After adjusting the choke I decided to fire her up. Got the muffs on and started cranking away. I immediately noticed the inline filter (haven't removed yet, but will), filled very quickly, telling me she's pulling more fuel now. After a short bit of cranking and pumping gas she fired up. She missed for a short bit and eventually smoothed out. She still seems to have a slight hiccup, but I think better than before. Throttle response is much better. I set the idle to about 700 rpms and let her run. She runs nice for sure, and the inline fuel filter is no longer draining itself, even at higher rpms. That is a huge relief to me. Now I just need to get her out in the water for a quick load test and see how she does. If she does well on the water today, I'll get her back home and get proper equipment back into her and clean her up. Sorry, forgot to get pics this time .

 

[Bondo]

I immediately noticed the inline filter (haven't removed yet, but will), filled very quickly, telling me she's pulling more fuel now.

Ayuh,..... The filter in the fuel pump is on the vacuum side, so if the gasket was bad, that'll explain why the fuel pump was failin',......

Get rid of that in-line filter, 'n find a place to mount a canister type water seperatin' fuel filter on there,.....
Once that's in-place, you'll never need to service the ones in the fuel pump or carb again,....

 

[Leveecius]

Ayuh,..... The filter in the fuel pump is on the vacuum side, so if the gasket was bad, that'll explain why the fuel pump was failin',......

Get rid of that in-line filter, 'n find a place to mount a canister type water seperatin' fuel filter on there,.....
Once that's in-place, you'll never need to service the ones in the fuel pump or carb again,....

Yes, I am going to get a fuel/water separator in there, was definitely a plan for sure.

But I have an update. I got the boat in the water again yesterday evening. Ran the boat around 1500rpm for about 20 minutes in the lake with no issues. After 20 minutes I decided to ease her into higher rpms and speeds. I got her to top out at 3000rpm and about 28mph, and that was as fast as she would go. I played with the tilt as much as I could and it would only slow down from where it was, but she wouldn't go over 3k rpms. When turning she would slow down a bit to about 2700 rpms, then once straight would catch back up to 3k. But other than that and the little bit of oil she burns from valve seals, she ran great. Over the winter she will get some quality engine maintenance done tho, so not worried about the seals at this point.

 

[achris]

3,000rpm at wide open is WAY too low. At full noise that engine should be spinning at between about 4,200 and 4,600rpm. You may have an engine issue that's dropped the revs, or your prop may be too big (too much pitch), or someone has changed the drive and put the wrong ratio without changing the prop....

Chris....

 

[Leveecius]

3,000rpm at wide open is WAY too low. At full noise that engine should be spinning at between about 4,200 and 4,600rpm. You may have an engine issue that's dropped the revs, or your prop may be too big (too much pitch), or someone has changed the drive and put the wrong ratio without changing the prop....

Chris....

Yeah, I figured it should be faster for sure, when out of load she will ping 6k no problem. I just don't know where to go from here to correct it. As far as I can tell, the drive is the right one, not 100% sure how to tell tho. And as far as the prop, I wouldn't know on that at all. I've had her to almost 4k (wide open) before catching the rope, so there still may be some issues. I'm sure the carb needs rebuilt, but Im not comfortable doing that. Other than that, I'm lost lol.

 

[achris]

Ok, you need to pull the prop off and check it over very carefully for any numbers. Could be stamped into the outer hub, or could be cast into the inside somewhere. Clean all the grease off and find it.

A couple of things worth checking on the engine. Make sure the throttle is actually opening all the way. Check and make sure the timing is set to the correct initial advance, and make sure it's advancing properly. Spinning to 6K no load isn't a good test... It proves very little. Also, check your compressions.

To check the drive ratio, put the drive in forward gear, remove the spark plugs and have an assistant watching the prop and counting turns. Turn the engine, by hand (do not use a socket on the crank bolt, you'll break it), and count the turns until you have 10 turns of the propeller (mark the prop with a white paint marker to make it easier for your helper).... The number of turns you needed to make on the engine to get 10 turns of the propeller, divided by 10 will give you the overall drive ratio. You should have a 1.98:1 reduction. That would mean 19.8 turns of the engine to 10 turns of the prop... The other way is to remove the drive, and do the same thing with the drive on the bench. Or you could pull the top cover off the drive and start counting teeth....

Chris...........