Maxum SCR 2300 4.3 Mercruiser 175hp not revving more than 3000-3500 RPM

[silviuradu95]

Hello guys,

I have a Maxum SCR 2300 from 1991 with Mercruiser 4.3L 175 HP paired with an Alpha One Gen 2 outdrive.

Took it out last week and saw that it does not rev more than 3000-3500 RPM.
There are no alarms, no engine weird sounds, idles good..
After 20-30 mins of going at 3000-3500rpm it just died at idle, cleaned 3 sparkplugs and it fired right back ( they were dirty, boat stood for more than a year ) .

What do you guys think it could be the cause ? I'm new on boating, especially Inboard engined since they are not really popular in my country ( Romania ).

Also what website do you guys use in order to purchase parts ?

Thank you alot for the help !

[mmwjr]

Welcome aboard!

I had a 4.3 in a previous boat that ran ok and had a smooth idle but had no compression in one cylinder due to a bad exhaust valve. I would check the other plugs and perform a compression test. Is this a new to you boat? If not when did it last run good? How old is the fuel and have you changed the filter?

[silviuradu95]

Thanks alot for the tip.

Just bought the boat. The fuel is fresh, the last time it run was more than a year ago. They said the filter is changed and also fresh oil. Checked the oil it really is fresh, they did the oil change and did not go on the water with it.. I will go to the boat in a couple of days and change the sparkplugs (they look ok but decided just to get new ones).

[mmwjr]

See if one plug looks different from the others. I take it you bought the boat without taking it for a sea trail? No one no no when buying a boat.

[silviuradu95]

They are all the same, I bought it with a sea trial, they just said it's caused by the carburateur needing to be adjusted. The price was good and the boat is in a very good condition.. I just think it needs a bit of love cuz in the last 4 years it was only took out 2 times.. it has around 700 hours.

[silviuradu95]

Now that you told me about your issue with one cylinder not working kinda got me worried. Will need to check

[mmwjr]

I hope it is something simple but I have seen many folks here who were told it just needs,… only to find a much bigger issue. Best wishes.

[mmwjr]

BTY do you know if the exhaust manifolds and risers were ever replaced? These as well as the engine are raw water cooled and if in salt water the exhaust typically needs to be replaced every 5 years. When they fail sea water gets into the exhaust stream and engine backpressure can draw the water into the cylinders which results in failure. This is what happened to the engine I had.

[silviuradu95]

They were replaced 4 years ago when it came to Romania. The boat was not used in salt water.

[mmwjr]

Originally Posted by silviuradu95

They were replaced 4 years ago when it came to Romania. The boat was not used in salt water.

Ok, that’s promising. With a boat this age it may be time to rebuild the carburetor. But I would first perform a compression test to verify the engines health.

[silviuradu95]

Thank you very much for the help.
Will purchase a compression test kit and try to do it soon, will update once I do that.
Hopefully no compression issues