Fear the inevitable...

[FBCoach]

20’ Celebrity Runabout. Mercruiser 4.3L. Engine info in pic. Boat has been running great. Pulling the kids on a tube and skis today. Been running about an hour on and off. Then... oil pressure dropped suddenly. Boat lost power. Engine started knocking. Doesn’t knock while idling. Going to take it to the pros. But any idea what i may be looking at? Thanks much.

 

[Rick Stephens]

Oil pressure plus knocking is probably a rod bearing. Bad news. Least is a tear down and full rebuild.

 

[Scott06]

Yeah I think you spun a rod bearing which means full rebuild. If you are handy and have access to a decent machine shop you can rebuild it fairly reasonably. Worst case a new base engine (tinned long block) is $3 k.install is extra But again if you are handy easy to do

if you prefer to have it done turn key probably $5-10k depending on what replacement engine and who does it

 

[FBCoach]

Uggh. Afraid of that. Any idea what may have caused this? Engine only has about 140 hours On it. Oil level was good before we started and pressure read 40-50 up to the point of the problem. When this occurred i checked again the oil was low. No sign of oil leak anywhere. Gear oil also had backed up into reservoir. Trying to further educate and do all we can to keep this from occurring again once fixed. Thanks much.

 

[Rick Stephens]

Weird things can happen. The oil pickup tube falls off, a piece of something jams in the pump, or a bearing spins. Until you get inside you won't know.

 

[RaceCarRich]

How low was the oil when you checked? A few ounces low or off the stick low?

Sorry for your luck.

 

[Scott Danforth]

Agree, from the description it sounds like a spun bearing

Potential causes:

• Crud in oil pan letting loose and plugging pickup screen resulting in loss of oil to motor
• crud in oil causing PRV spring and piston to stick open resulting in loss of oil to motor
• Low oil level and sloshing while under load (pickup draws in air, the bearings loose oil film)
• prior bearing damage from acid build-up in the oil

Was the 140 hours over 3 years or 30 years?

Was the oil changed every year?

 

[FBCoach]

Oil was normal when i checked it before we went out. Oil was extremely low when i checked it after the incident. Yet, couldn’t see signs of oil in the engine compartment. The 140 hours was over the life of the boat. Family member had more money than time when they bought it. The boat sat in storage for over 5 years. We moved to a lake and my uncle gave it to me. Rotted during this time. I did a complete hull and transom rebuild a few years ago. Another reason this sucks so - lot of time and money in it already. See link below. Cleaned the motor and carb real good (i thought last summer as we got her running. Winterized her after last summer. Added a new gimbal bearing, replaced All fluids and Did tune up This April.

https://forums.iboats.com/forum/boa...ity-200-deck-stringer-and-transom-replacement

 

[FBCoach]

Hard to find anyone who wants to tackle this project and really don’t have the time at this point. Any suggestions on where to find replacement Motors at a quality price? Looking at all options.

 

[Rick Stephens]

Just went through your rebuild thread. Beautiful job. See why you like the boat.

Have to let someone answer the motor question. Never bought one, I always have a bit more time than dough.

 

[Searay205]

You need to find where the oil went. I don't buy the crud excuse in oil causing the problem. Hardest thing about pulling a boat engine is finding engine hoist tall enough. After that its all easy.

 

[Searay205]

4.3 in 20 foot boat a dog. I go with 350MAG. get used engine of eBay from freshwater service with ECM. You sure don't need a 350MAG but same price as 5.0MPI so might as well get an extra 40hp for free.

 

[Searay205]

Even carburetor 5.0 better than dog 4.3. Probably get whole engine under $3K

 

[Rick Stephens]

Even carburetor 5.0 better than dog 4.3. Probably get whole engine under $3K

And you are nuts. Need exhaust, carburetor, potentially accessories, and potentially motor mounts since a V8 is 3 inches longer to the mounts. Nobody gonna get away with anywhere near $3k. Save the baloney for someone without a brain.

 

[achris]

4.3 in 20 foot boat a dog. I go with 350MAG. get used engine of eBay from freshwater service with ECM. You sure don't need a 350MAG but same price as 5.0MPI so might as well get an extra 40hp for free.

Even carburetor 5.0 better than dog 4.3. Probably get whole engine under $3K

I beg your pardon!

A 4.3 is about the best engine for a 20' boat. In fact, I put my old 4.3LX into a friends 23' boat, which had a carbed 5 litre V8, and we got it 6 knots quicker with the 4.3 than the 5 litre.

Chris.......

 

[Lou C]

Yes well set up they are great in a boat that size, 100+ lbs less weight and very economical as well. I was always surprised how little fuel my boat actually uses cruising on the small primaries of the Rochester Quadrajet….

 

[achris]

... very economical as well. I was always surprised how little fuel my boat actually uses cruising on the small primaries of the Rochester Quadrajet….

I have the MPI, and at 27 knots it's only using about 1.2 litres per nautical mile. There wouldn't be a SBC V8 on the planet that could match that!

Chris....

 

[Scott06]

Hard to find anyone who wants to tackle this project and really don’t have the time at this point. Any suggestions on where to find replacement Motors at a quality price? Looking at all options.

Try Michigan motorz they have remanufactured and new engines.

 

[FBCoach]

Ok - where we are. First, the lake i live on has a motor restriction. I already have the largest available.

I found a local guy with a great reputation who said he can rebuild mine, or get a refeb - warranted long block replacement. He recommends the referb. Would you all concur? Thanks much.

 

[achris]

Until the old engine is stripped and assessed, you've no way of knowing. If it's just a rod bearing, you could just pull the crank and have that machined, new bearings and you're away. Do most of the labour yourself and it'll be a very inexpensive fix.

Chris........