Gt150 rebuild

**jbower** · 12-13-2018, 05:41 PM

Hey everyone new guy here in Indiana. I am currently rebuilding my gt150 and trying to get as much info as I can. It’s an 1985 and I have 200 intake filler blocks, the good heads off a 200. Anyways I knew it was going to need attention when I bought it due to low compression, I fished a big tournament with long runs and in practice it locked up and a few minutes later started right up I limped it threw the tournament hoping not to do to much damage and now I have it apart. Everything looks great but one of the middle cylinders is scarred on both intake and exhaust side. Any info on what would cause that would be great. Now I’m seeking advice on porting and polishing and getting the most I can without going overboard

**rock** · 12-13-2018, 06:18 PM

Welcome to the site. Post some pics of the piston and cyl and someone will have a guess.

Rock

**jbower** · 12-13-2018, 06:22 PM

Click image for larger version.

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Here’s piston. I’ll have to take a pic of the cylinder tomorrow when I get back to the shop

**racer** · 12-14-2018, 07:51 AM

Looks like a heat issue which is odd for a center cylinder. #4 would be more likely than 3. I would check the water diverters as they could cause this type of issue.

**jbower** · 12-14-2018, 08:32 AM

thanks racer. there is a chance that i had hit some floating debri such as weeds and what not..the tournament was down in tennessee after a flood and stuff was everywhere. ive seen your name in alot of crossflow threads, are you by chance still doing any work on these?

**jbower** · 12-14-2018, 02:24 PM

diverters are all in. when this incident happened i immediatly premixed fuel because i thought it had appeared not to of used as much oil as a couple of 40 mile runs should have. i dont know what happened. i have 1 3/8 carbs that came on it and the 200 also has 1 3/8s carbs.

**Merc 2.5** · 12-14-2018, 02:40 PM

Possibly leaned that cyl out? There is a great video on YouTube with a guy rebuilding omc v6 , if your rebuilding yourself and is 1st one, its worthwhile to watch it. Lots of helpful hints he gives, you may have built hundreds tho

**jbower** · 12-14-2018, 02:42 PM

ive built a etec 225 a couple yamaha 4 strokes and some other 2 strokes..nothing im scared of but i am a little scared of porting

**Merc 2.5** · 12-14-2018, 02:48 PM

way I understand it a unsteady hand can ruin one , wrechin2 can give u the specs or tell u exactly what u need to do , very very good machine guy on these outboards , theres quite a few on here that could prob help u out. If your interested PM me and I'll send his # over to u , he will put u on rite path, hes done lots of members motors here

**racer** · 12-14-2018, 03:19 PM

The diverters tend to block off the passage way toward outside of block. If it were an oil issue all the cylinders would have damage.

No I dont build engines these days more or less retired.

**H2OPERF** · 12-14-2018, 05:43 PM

Take a pic of the top of the piston may just be lighting but looks kinda light...

**jbower** · 12-14-2018, 06:58 PM

that Piston was a little drier than the rest. I guess I probably can answer my only question at the end of the tournament it wouldn’t run without the enrichment on. Completely forgot about it

**Merc 2.5** · 12-15-2018, 02:24 PM

Prob sucked trash n carb or sumthin, I scuffed #6 on a 2.4 frm piece trash n carb

**racer** · 12-16-2018, 08:46 AM

From the view of posted pic does not look to have any detonation.

**jbower** · 12-16-2018, 11:22 AM

I’ll get some pics of the cylinder itself tomorrow. Intake and exhaust sides are both tore up at the ports. All other 5 cylinders look perfectly fine though