sms986
Petty Officer 1st Class
- Joined
- Sep 18, 2017
- Messages
- 334
Hello all,
I have two 1998 gp1200 engines that I am putting into a jet boat. Working on drawing up some designs and stuff for the engines and I have a bunch of things I'm looking for.
The exhaust-I know they make some sort of a "triple exhaust" for these, but I can't find much on it. Is it worth it?
Water cooling route inside the engine. Is there a diagram for this anywhere? I want to completely separate the exhaust gas flow and water flow. Was considering something similar to a mercruiser Y pipe for the exhaust gas stream with flappers in it for check valves so I can route the exhaust down right between the two jets. I do not want to mix my water and exhaust gasses. Period. From what it looks like so far, the water doesn't seem to mix with gases until after the expansion chamber. Is this correct? If so, I can make an exhaust downpipe that collects the exhaust gasses and water separately and discharges them both separately out through the transom. I don't want the headache of water getting into the engines.
One of the engines didn't run right when I bought them. Previous owner said the ski would run fine low, but at WOT it would run hard for a few seconds then bog down. Upon inspection, I found a bolt on the head hand tight and the piston was pretty well water washed. Spark plug on the MAG cylinder was also wet after he ran the skis for me when I bought them. To me, it seems water was getting in here at the head gasket. I just checked the deck and it's fine, not warped. Don't care about the head. It's a RIVA head and I'm dumping it off for an OEM anyway. I also noticed the center piston was all scored up and and the center crank had some surface corrosion. Head for this cylinder was all pitted from probably a recent piston exploding. The crank does seem fine though. No up and down or side to side play. Rods don't move up and down either, just side to side like normal. Rotates freely. Cylinders don't look bad, but I'm going to deglaze.
I'm very familiar with yamaha two strokes, but not the open water cooling system for the skis. Bought these specific engines because I think the Yamahas are among the best. However, as far as the major differences of jet ski engines in general, I'm a novice. Have done a good amount of work on outboards, but never jet skis. Really just looking for any querks in this engine design or specific oddities.
Thanks!
I have two 1998 gp1200 engines that I am putting into a jet boat. Working on drawing up some designs and stuff for the engines and I have a bunch of things I'm looking for.
The exhaust-I know they make some sort of a "triple exhaust" for these, but I can't find much on it. Is it worth it?
Water cooling route inside the engine. Is there a diagram for this anywhere? I want to completely separate the exhaust gas flow and water flow. Was considering something similar to a mercruiser Y pipe for the exhaust gas stream with flappers in it for check valves so I can route the exhaust down right between the two jets. I do not want to mix my water and exhaust gasses. Period. From what it looks like so far, the water doesn't seem to mix with gases until after the expansion chamber. Is this correct? If so, I can make an exhaust downpipe that collects the exhaust gasses and water separately and discharges them both separately out through the transom. I don't want the headache of water getting into the engines.
One of the engines didn't run right when I bought them. Previous owner said the ski would run fine low, but at WOT it would run hard for a few seconds then bog down. Upon inspection, I found a bolt on the head hand tight and the piston was pretty well water washed. Spark plug on the MAG cylinder was also wet after he ran the skis for me when I bought them. To me, it seems water was getting in here at the head gasket. I just checked the deck and it's fine, not warped. Don't care about the head. It's a RIVA head and I'm dumping it off for an OEM anyway. I also noticed the center piston was all scored up and and the center crank had some surface corrosion. Head for this cylinder was all pitted from probably a recent piston exploding. The crank does seem fine though. No up and down or side to side play. Rods don't move up and down either, just side to side like normal. Rotates freely. Cylinders don't look bad, but I'm going to deglaze.
I'm very familiar with yamaha two strokes, but not the open water cooling system for the skis. Bought these specific engines because I think the Yamahas are among the best. However, as far as the major differences of jet ski engines in general, I'm a novice. Have done a good amount of work on outboards, but never jet skis. Really just looking for any querks in this engine design or specific oddities.
Thanks!