Blueghost924
Petty Officer 1st Class
- Joined
- Sep 19, 2013
- Messages
- 250
Hi, I have a 1987 21 foot Renken that I bought recently, and I'm looking to replace the Mercruiser 470 4-cylinder engine that's in it. The manager of a local chemical shop, who is also a boat owner, recently removed an entire Mercruiser 470 170 HP from his boat that would be a perfect match for mine. He removed his 470 from his boat (a 60's model he recently bought) to put in an original model. I've been told that this 470 has been rebuilt and has low hours (but he doesn't know how low).
I went to the shop this morning to look at the engine, and one of the shop guys brought out a battery. I sprayed some lubricant down the spark plug holes. I removed #3 spark plug, hooked up my compression gauge and we hooked up a battery to the starter. We grounded it to a bolt on the exhaust manifold. The engine turned over very slow, and got up to about 45 PSI on the compression gauge (but at least it did turn over and is not locked up). Supposedly the battery was 13.5 volts (which may not mean much). We then removed the spark plugs completely from #2, #3 and #4 cylinders and hooked up the battery. It turned over a little faster, but still too slow than normal. The shop guy then plugged in a portable cart battery charger, hooked that up to the battery and then hooked the battery to the boat engine starter (with the 3 plugs out still). The engine still turned over slow. As it was turning over slow, I put my hand over #2, #3 and #4 spark plug holes and could feel air popping out. Good sign?
Anyway, I'm hesitating buying this engine. Overall, it appears to be in good shape, normal wear on the outside, and doesn't appear to have any leaks. The reason it turns over real slow, I'm thinking:
1. The battery is still not giving it enough juice (most likely).
2. The starter is starting to give out or there's something wrong with it (doesn't seem likely).
3. There's something wrong internally with the engine (may not be the case).
Thoughts?
I went to the shop this morning to look at the engine, and one of the shop guys brought out a battery. I sprayed some lubricant down the spark plug holes. I removed #3 spark plug, hooked up my compression gauge and we hooked up a battery to the starter. We grounded it to a bolt on the exhaust manifold. The engine turned over very slow, and got up to about 45 PSI on the compression gauge (but at least it did turn over and is not locked up). Supposedly the battery was 13.5 volts (which may not mean much). We then removed the spark plugs completely from #2, #3 and #4 cylinders and hooked up the battery. It turned over a little faster, but still too slow than normal. The shop guy then plugged in a portable cart battery charger, hooked that up to the battery and then hooked the battery to the boat engine starter (with the 3 plugs out still). The engine still turned over slow. As it was turning over slow, I put my hand over #2, #3 and #4 spark plug holes and could feel air popping out. Good sign?
Anyway, I'm hesitating buying this engine. Overall, it appears to be in good shape, normal wear on the outside, and doesn't appear to have any leaks. The reason it turns over real slow, I'm thinking:
1. The battery is still not giving it enough juice (most likely).
2. The starter is starting to give out or there's something wrong with it (doesn't seem likely).
3. There's something wrong internally with the engine (may not be the case).
Thoughts?
