Any comments on how to renew my engine

[sjc204]

I had almost given up on my engine until I found this forum. I hope someone might give me some new ideas on it. Here's the story.

The engine has been on the boat from new, around 1980ish, and was in the family with my father from about 1990. It was on fresh water (Norfolk) until about 1998, since then on sea water.

Originally it had a car alternator fitted, running from a pulley above the flywheel. I removed that a few years ago when I started having overheating problems.

The cause of the overheating problems was salts clogging the water channels in the inlet manifold. I have cleaned them many times, often with new gaskets and thermostats.

I have created a new bit of plumbing (with two diverter valves) that allows me to flush the engine with fresh water after use.

Another time the exhaust box sprang a leak, and the engine started to flood the boat whenever the engine was running. No problem though, I was able to replace the exhaust box with a new one from a company in Norfolk (which specialised in this engine but I think may no longer be running). They were having them cast by a third party.

On one occasion a bubble of air appears to have caused a corrosion hole in the top of the cylinder head. (Corrosion is worst where there is water and air.) I was able to get this welded and re-machined, and rebuilt the engine successfully. No part had any significant amount of wear, compared to the limits in the book.

More recently I have had lots of difficulty starting the engine. The compression seems good, there is a spark, and there is fuel. From various advice I concluded it might be due to old petrol (the petrol is always old in a boat used occsionally). So I have replaced the old metal fuel tank (which never sealed properly) with an airtight plastic one that should keep the volatiles in a bit better. I also replaced the fuel pipes and priming pump and removed the old filter. The result was that the engine ran fine for twenty minutes or so, while I wrote up the log book. After that the engine stopped and I have never been able to start it again. There is still compression, spark, and fuel getting through.

My plan (unless you have a better idea!) is to replace the powerhead with a "new" honda engine from a BF100 outboard. I have got one that runs nicely, and another for spares. Now reading this forum I wonder if I still have a chance someone can tell me how to put the existing engine right. One thing I am not sure of is whether the carburettor could be at fault (although I have stripped and cleaned it), or possibly I am not setting it up well enough. I now have two carbs to swop with...

I have also thought that if I could put in an electric start I might get it running again - it takes a very well set-up engine to spark and fire on the couple of turns you can get with a pull start.

All ideas welcome! Also if I can help anyone from my experience I'd be happy to.

Steve

[John Smith]

(08-04-2010 05:02 PM)sjc204 Wrote:  I had almost given up on my engine until I found this forum. I hope someone might give me some new ideas on it. Here's the story.

The engine has been on the boat from new, around 1980ish, and was in the family with my father from about 1990. It was on fresh water (Norfolk) until about 1998, since then on sea water.

Originally it had a car alternator fitted, running from a pulley above the flywheel. I removed that a few years ago when I started having overheating problems.

The cause of the overheating problems was salts clogging the water channels in the inlet manifold. I have cleaned them many times, often with new gaskets and thermostats.

I have created a new bit of plumbing (with two diverter valves) that allows me to flush the engine with fresh water after use.




Another time the exhaust box sprang a leak, and the engine started to flood the boat whenever the engine was running. No problem though, I was able to replace the exhaust box with a new one from a company in Norfolk (which specialised in this engine but I think may no longer be running). They were having them cast by a third party.

On one occasion a bubble of air appears to have caused a corrosion hole in the top of the cylinder head. (Corrosion is worst where there is water and air.) I was able to get this welded and re-machined, and rebuilt the engine successfully. No part had any significant amount of wear, compared to the limits in the book.

More recently I have had lots of difficulty starting the engine. The compression seems good, there is a spark, and there is fuel. From various advice I concluded it might be due to old petrol (the petrol is always old in a boat used occsionally). So I have replaced the old metal fuel tank (which never sealed properly) with an airtight plastic one that should keep the volatiles in a bit better. I also replaced the fuel pipes and priming pump and removed the old filter. The result was that the engine ran fine for twenty minutes or so, while I wrote up the log book. After that the engine stopped and I have never been able to start it again. There is still compression, spark, and fuel getting through.

My plan (unless you have a better idea!) is to replace the powerhead with a "new" honda engine from a BF100 outboard. I have got one that runs nicely, and another for spares. Now reading this forum I wonder if I still have a chance someone can tell me how to put the existing engine right. One thing I am not sure of is whether the carburettor could be at fault (although I have stripped and cleaned it), or possibly I am not setting it up well enough. I now have two carbs to swop with...

I have also thought that if I could put in an electric start I might get it running again - it takes a very well set-up engine to spark and fire on the couple of turns you can get with a pull start.

All ideas welcome! Also if I can help anyone from my experience I'd be happy to.

Steve

HI Steve.
I had a similar problem. My engine suddenly stopped whilst I was manuovering to enter the marina. Had to be rescued by the marina workboat. Subsequent investigations (and much time taken) indicated a thouroghly blocked Carb', probably corrosion in the very small internal drillings.
Solution, get a new carb'.

p.s. A collegue of mine was stranded out on the water when his engine suddenly stopped. He discovered that the wiring connections were very corroded. Try checking yours carefully.

Good Luck.
John

[sjc204]

HI Steve.
I had a similar problem. My engine suddenly stopped whilst I was manuovering to enter the marina. Had to be rescued by the marina workboat. Subsequent investigations (and much time taken) indicated a thouroghly blocked Carb', probably corrosion in the very small internal drillings.
Solution, get a new carb'.

p.s. A collegue of mine was stranded out on the water when his engine suddenly stopped. He discovered that the wiring connections were very corroded. Try checking yours carefully.

Good Luck.
John

Hi John,

I'll strip down one of the spare carbs I have got and if it looks ok I'll give it a try (although the one that's already on looks ok!).

Many thanks for your encouragement, and I'd be very glad to hear from anybody else.

Steve

[John Smith]

Hi.
I've had another thought about why your engine stopped after it had been running for twenty minutes. At the risk of stating the obvious, if you have installed a new plastic fuel tank, it's just possible that the air bleed hole in the tank is blocked. Alternatively, if the tank is one of the portable type with a scew type of air bleed then is the screw loosened?

[billyjmcd]

Hi Steve

check the exciter coil on the primary BROWN it should be 330 ohms and the yellow 1.4 ohms [NOTE the manual is wrong] i have just changed mine because i was getting a spark but not a good one and the resistance reading on the brown lead was 280 ohms once changed it was running great.
I removed my thermostat years ago and never had any problems my thinking being that if i leave the water inlet valve open for 30 mins after stopping the engine the water will drain out of the engine.
I have just bought a engine off the internet and am going to Norfolk in the morning to collect it.
good luck
james.

[sjc204]

Hi James,

Thanks for that. As I have a spark I have never checked the coil - all the contacts are good so I had assumed it was fine. However I now have two of these to swop with (from outboards).

Have you got your new engine? Is it any good, is it MB2A? was it from a dealer?

[billyjmcd]

Hi Steve.
I have just got back tonight the engine[nb2a/50s] looks good but i shall check it out tomorrow but i am very hopeful i will let you know .
james.
p.s. check on the carb that the plunger is working o.k.

[billyjmcd]

(20-04-2010 08:47 PM)sjc204 Wrote:  Hi James,

Thanks for that. As I have a spark I have never checked the coil - all the contacts are good so I had assumed it was fine. However I now have two of these to swop with (from outboards).

Have you got your new engine? Is it any good, is it MB2A? was it from a dealer?

Hi Steve
How are you getting on? yes it was a mb2a/50s engine that i bought i have just completed it today,there was oil in the engine with laying down to bring it home and although there was a spark it would not start i then found that the compresion was down on no1 cyl. on further investigation i found that the timing was out by about 2ml after resetting the timing i now have a nice running engine after running flushing oil and then changing engine&leg oil.
might be worth checking your timing.

If i can help get in touch
james.

[sjc204]

Hi, I have checked the electrics as suggested by Billyjmcd, all fine. I also removed the camshaft pulley and checked the weights were in place (they looked brand new). I replaced the belt as I thought that some slackness could interfere with the ignition timing, and I reset the timing by lining up the marks as carefully as I could.

The engine started, ran for a little while. I didn't get round to setting up the fuel mix and idle speed. After a while it stopped again, but I got it to run a couple of times, with a great deal of pulling. I gave up when my shoulder hurt too much.

Now I'm thinking the engine has to come out, and the BF100 can go in.