Advice on buying boat indmar 5.7l

[Dhayward84]

Hey I’m new to the forum but have been around boating with my dad my whole life. Looking to get my first boat and also looking for advice. We are looking to buy a 1978 30’ sea ray with twin inboard indmar 5.7l engines. I see it seems to be common having issues with motors with low WOT rpm and I’ve seen the list on the sticky. We ran a compression test and all was well 150 on almost all of them and 148 on cylinder 3.

On the sea trial the starboard engine stopped at 3000rpm not just a bad gauge either. And the port motor revved to 4500.

The fuel pump is working making correct pressure lines aren’t clogged gas is new according to the owner.

Assuming this is an issue with the carbs is this boat safe to run in this condition to get it home to work on? We have a 3-4 hour ride to get it home and I just don’t want to cause damage to the engine on the way there. Should I just buy a new carburetor for this engine swap it and try it or should I try something else?

 

[Dhayward84]

Also note the owner had these engines installed 3 years ago. Not sure what exactly was replaced his paperwork is not descriptive so I’m not sure if it was short blocks or full long block setup or what.

 

[alldodge]

Assuming this is an issue with the carbs is this boat safe to run in this condition to get it home to work on?

This is a question that only you can answer. Not sure right now that the carb is the issue, might be other things like the distributor not advancing or timing is incorrect, a plug not firing correctly

If its flooding then its just going to fowl the plugs, but if its running lean it can destroy the motor.

What about swapping the carb with the port motor to see if it problem moves?

 

[Dhayward84]

That’s a good idea I didn’t think of. The only big concern is the boat is far away and I don’t have anyone to work on it there for me so I kind of have to do it in one shot and fix it or run it home

 

[Scott Danforth]

What about fixing the carb or paying someone to fix it so you dont damage the motor

 

[Lou C]

that sounds like a risky plan at best, the carbs are the least of the issues! has the boat been checked for wood rot?

 

[KD4UPL]

I personally would not be comfortable hoping onto a 41 year old boat that I have no experience with and running 4 hours to get home. There is so much than can and will go wrong. Just because the owner said the fuel is new doesn't mean it is. It doesn't tell you how much water or other crud was in the tanks already when the new fuel was put in.
How new are the impellers? Is their water in the drive oil? Does the fuel gauge work? Are there any leaks in the hull? Does it have an anchor if you need one? Does it have all the lights, fire extinguishers, etc. that you'll need if you get stopped and checked?

 

[HT32BSX115]

1978 30’ sea ray with twin inboard indmar 5.7l engines.

Howdy,

Welcome aboard!

Well, low WOT RPM can be caused by several things.

There's a list here: https://forums.iboats.com/forum/eng...d-inboards/10530621-adults-only-no-exceptions

#15 speaks to low WOT RPM but there's a LOT of other stuff there!

If those engine are only 3 years old and fairly low time, I wouldn't run it at any RPM for 4 hrs until I found the problem and fixed it.

A few causes of low RPM can permanently damage an engine.


Regards,


Rick


Hey KD4UPL, You wouldn't happen to have a "cousin" Craig in Anchorage, AK would you?