1988 Shamrock engine problems

chris88

Cadet
Joined
Jun 25, 2005
Messages
9
We just moved down by the bay and the guy left a 1988 Shamrock 20ft with the house. The boat runs good but it doenst idle and it keeps over heating. Its got a 302 ford/pleasurecraft in it. Its a great boat but we keep having little problems with it. What temp T-stat do you guys run? What temp should this engine be running at? Were good until we get around 2500 rpms than we start having trouble. <br />Chris
 

jeff13601

Chief Petty Officer
Joined
Apr 30, 2005
Messages
593
Re: 1988 Shamrock engine problems

You need to give more info on engine and drive
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: 1988 Shamrock engine problems

Someone say BARNEGAT BAY?! You should post using the letters O.M.C. & Ford in your header. Pretty sure that's what you have, I don't know jack about O.M.C., but there are alot of guys here who do. Now the 302 Ford however.......J
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 1988 Shamrock engine problems

is it fresh or salt water cooled? do you have any of the maint history such as seawater pump replacements and riser/manifold replacements?
 

chris88

Cadet
Joined
Jun 25, 2005
Messages
9
Re: 1988 Shamrock engine problems

Barnegat Bay is right. The impellar was just replaced. It only has 480 hrs on it. The manifold looks original or at least OEM. Its salt water cooled. What else would you need on the engine? <br />Thanks<br />Chris
 

elpaso

Petty Officer 1st Class
Joined
Jun 27, 2003
Messages
264
Re: 1988 Shamrock engine problems

1988 Shamrock 20' were made in Cape Coral, Fl. Ford 302 - inboard -<br />with deep keel - to protect prop in shallow coastal waters.<br />Very popular in Southwest Florida. Engine conversion, was by Pleasurecraft.<br /> <br />Overheating at high speed is a lack of water flow problem. If this is the<br />boat that I think. What is the exhaust system from exhaust manifolds<br />to transom. They came from factory with 4" pipe. Are the manifolds center or rear risers? I owned a 1983.
 

chris88

Cadet
Joined
Jun 25, 2005
Messages
9
Re: 1988 Shamrock engine problems

The exhaust pipes or hoses are 4 inch. Im not sure if the manifolds are center or rear risers. How would we be able to fix the lack of water flow? What temp T-stat is right for these boats? What temp should these engines be running at? The boat is great but we just keep having problems with it overheating. <br />Chris
 

prockvoan

Chief Petty Officer
Joined
Jul 27, 2004
Messages
512
Re: 1988 Shamrock engine problems

I had one of those boats,my last one,Great one at that.The engine had a 160 drg t-stat in it.<br />After running it for about 8 years,I had repower it with a 351 Marine power bobtail engine.At the time it cost me around $4,800 for the engine.What a big improvement on how the boat handle.Went from 12 gals gas per hour to 7 per hour,pick up 9 mph at 3300 rpm's,prop pitch was 13x13 went to 13x19.WOT speed was 47mph loaded,cruise speed was 36mph @3300rpm's,reading were use from a GPS.The problem was it wasn't big enought for the family,now I am looking to down size due to the kids are out of the house.
 

chris88

Cadet
Joined
Jun 25, 2005
Messages
9
Re: 1988 Shamrock engine problems

Damn, our boat hits like 33 at around 3400. Yours had a bigger engine but still thats a big improvement. This boat is great because of where the engine is. Its right in the middle of the boat instead of in the back like an I/O. Thats the great thing about an inboard. The engine was 4800. With an I/O the engine would be 4800 and the out drive would be another 5000. What size Shamrock did you have? We're running a 165 degree T-stat now. <br />Thanks<br />Chris
 

nms1991

Cadet
Joined
May 18, 2004
Messages
25
Re: 1988 Shamrock engine problems

Engines that used freshwater to cool the block used a 143 degree thermostat. But problem does not sound like a bad thermostat but a water flow problem. The engine should have center dump risers and they should use 3" inside diameter hoses. Idle problem could be a adjustment on the carb or it may need to be rebuilt. First thing to check on the cooling problem is to check the trans cooler for seaweed clogging the tubes. then check your impeller to make sure it is not damaged, if it is damaged it is the sherwood part number 9959k and it should have all the gaskets you need. Then go to the thermostat housing to see if it is blocked or not flowing right. then check your exhaust manifolds for restriction in the cooling passages then you will want to check your exhaust hoses and mufflers if equiped for loose or broken baffles.
 
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