Engine Power

captainron19

Seaman
Joined
Feb 10, 2012
Messages
54
OK So here it goes...

1989 Robalo 2320, center console walk around (no cuddy cabin). It is 23' with an 8' Beam. Both engines are outboard Mariner V6 150's (1989) with a 25" shaft.

Both engines ran strong when I test drove the boat.... had it out with an full open throttle for almost 45 minutes continuous on the bay/inlet with a heavy chop and wind blowing 20-25 so the engines really got a good test. The first run i took it out on the river a week ago with a flat calm my starboard engine stalled twice (go figure). I thought it was just some air in the fuel line but the guy at Marina did a compression test for me and 5 cylinders were good (all 120-125) but the one cylinder had 0 compression. Me and the mechanic at my firehouse took the head cover off and found a blown piston.

I then took it to a marine shop specializing in Mercury and he gave it a look over and confirmed that the piston and cylinder were damaged to the point where it is un-repairable.

I went to a few other Marine shops to inquire on my options. One guy actually said that if I choose to go to a single engine (around 250 HP) I would actually increase my speed and fuel efficiency because the 2 engines on there now weigh almost 425 pounds each. Plus he did not recommend re-powering the bad engine since it is very old.

He also told me I could probably get almost $1500 for the good engine and anywhere from $300-$500 for the bad engine since people are always looking for parts. So I would plan on trading them or selling them to help offset any costs. I know I cannot afford a brand new outboard and I have seen a few good ones online and on ebay for the price range of about $4k -$5k.


The only other thing is..... if I choose to go with a single engine I was told it would have to have a 30" shaft. Right now my 2 Mariner Engines are 25" shafts but they are offset on the port and starboard sides so if I go with one engine it will be in the center of the transom where it is the tallest so the shaft would need to be 30"

Do I seem in the ballpark. I have heard from several people that I could go with a 225 - 250 HP single engine but one guy told me to check into the possibility that my boat is designed to have 2 engines and will not operate properly with a single engine. I know the max HP allowed for it is 300

I am not looking for imense speed..... I just want to get from point A to Point B with mostly operating in the river and bay with the ocassional trip just out of the inlets into the ocean.

Can anyone offer and input if I am on the right track?
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: Engine Power

You may just want to get another opinion. Most outboards when damaged beyond boring tolerance can be re-sleeved if the block is not cracked. It does take special tools and skills and is not cheap, but it beats buying another engine.

Go onto the Wiseco website. They used to sell sleeves for Merc. and OMC engines--don't know if they still do. Don't know if anyone makes a 30 inch shaft engine and if you can not find one you would need to get an expensive transom set-back box. Lots and lots of work adapting cables and steering etc. If at all possible I would repair the existing engine or buy a short block on the auctions.
 

Bob_VT

Moderator & Unofficial iBoats Historian
Staff member
Joined
May 19, 2001
Messages
26,065
Re: Engine Power

Absolutely get it sleeved. I agree with Frank ^^^^^
 

Philster

Captain
Joined
Sep 15, 2009
Messages
3,344
Re: Engine Power

As I read up to the point where the OP said, "I ran them wide open for 45 minutes", I thought, "With old outboards, that is just begging for a lean condition. Wonder where this story is going...?"

And whatya know. :facepalm:

A lean condition will destroy a piston.

.
 
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