Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

rtpassini

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Im going to look at a boat this weekend. I can't find any info on this boat. The guy couldnt send me any pics so I can't share those. I'll check overall condition. the floor, and transom best I can. (ill bring a screwdriver to tap the back).
Any pro's or cons with I/O? or things to look for?

Heres what he told me
"1979 18 ft V hull Thompson boat. I'm selling cause in the spring I'm upgrading bought as a project boat. Stuck over a grand in the motor. But now runs amazing. These are the things all redone
2new solenoids
All wiring brand new
Spark plugs
Carb
Starter
All boots replaced
Water pump
Ripped old seats out bought replace ments
Motor cover completely redone
Complete tune up
New battery
Motor tilt
New tires on trailer
Water pump

Only thing that needs to be fixed is the speedometer gauge doesn't work and one of the trailer lights needs to be replaced. Boat runs great inboard outboard 4 cylinder merc cruiser 180hp with trailer."
 

southkogs

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

Without pictures it's hard to guess ... and without actually seeing it, it's really hard to know.

Here's my concerns (right off the bat): I don't think the seller knows what they really have. A 4cyl 180HP doesn't sound right. Even worse, I'll bet that will turn out to be the dreaded Mercruiser 470.

It all just sounds a little weird.

What other choices to you have?
 

rtpassini

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

So far, ive bought 2 boats in my lifetime. Both times they got the year of the boat and motor wrong. the last one even got the HP wrong when talking to him. even though its printed in big numbers on the motor.

Im expecting the same in this instance.
Im assuming this is what it is http://www.fiberglassics.com/wiki/i...onbulletin79.jpg/463px-Thompsonbulletin79.jpg

I know NOTHING about I/O. What should I look for in terms of good models, bad models, or obvious issues I can see.
 

jayhanig

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

The best thing you can do is demand a test ride. You probably won't get one this time of year but that's the best thing you can do. Short of that, check every inch of that deck to be sure there's no spring or mush in it. Likewise the transom needs to be stressed by trying to flex the outdrive (it shouldn't). Look for rust on the outside of the engine and note how high it goes if there is any. It's had water that high in there. Pull the dipstick and look for at the oil for evidence of water contamination. If it's a salt water boat look hard at the exhaust manifold and the riser for signs of impending failure. Look underneath the engine for stains or leaks.

And BTW: the GM built 4 cylinder Mercruiser engine is 3 liters/181 ci and develops between 120-140 HP depending on the year.
 

ezmobee

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

I think you're going to find out it has the Mercruiser 470 motor in it which for me would be a non-starter. It was a problematic design and has a number of NLA parts. For I/O's you want Mercruiser or Volvo with Chevy based engines.
 

southkogs

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

I know NOTHING about I/O. What should I look for in terms of good models, bad models, or obvious issues I can see.
Buyin' used you kinda' have to roll with the market, y'know?

Not knowing exactly what you want to do on a boat (fish, ski, cruise, swim, etc.), where you're boating (Great Lakes, inland lakes) I took a quick spin through the CL listing I think that Larson you were looking at. With all of the offerings I saw, I would look at THIS boat or THIS boat.

If you're lookin' specifically at I/O's (seems like you know a thing or two about OBs) - follow EZ's call. Chevy based Mercruiser or Volvo.
 

Part-time

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

Like the others said... if it's truely 180hp it's most likely the in-line 6. If that's the case, just run.
If it's the 3.0 4 cyl (120 or 140hp) just check that there is no water in the oil.
Check that the block is not cracked, or the exhaust log.
Lift the outdrive all the way and check the belows for cracks or wear.
The exhaust below doesn't mater much(the bottom one) but a tiny hole in the shift cable or drive belows can let a lot of water in the boat in very little time (this I know from personal experience).
If these have been serviced then the gimbal bearing probably has been serviced as well.
If the belows look as old as the boat then you know what else to look forward too!
Check that the bottom bolts that hold the outside part of the outdrive to the inside transom plate are not loose as I have found is often the case when the transom goes soft.
Good luck.
P-T
 

ezmobee

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Re: Thoughts? 79 Thompson 18' open bow 4 cyl merc cruiser

Like the others said... if it's truely 180hp it's most likely the in-line 6. If that's the case, just run.

The in-line 6 isn't too bad. It's the big 4-cylinder you don't want. Most commonly called the Mercruiser 470 but also can be seen as 170, 190, 485 and 488. All are 3.7L 4 cylinders.
 
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